TI1 ADS1198 Low-power, 8-channel, 24-bit analog front-end for biopotential measurement Datasheet

ADS1294, ADS1294R
ADS1296, ADS1296R
ADS1298, ADS1298R
SBAS459I – JANUARY 2010 – REVISED JANUARY 2012
www.ti.com
Low-Power, 8-Channel, 24-Bit Analog Front-End for Biopotential Measurements
Check for Samples: ADS1294, ADS1294R, ADS1296, ADS1296R, ADS1298, ADS1298R
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Eight Low-Noise PGAs and Eight
High-Resolution ADCs (ADS1298, ADS1298R)
Low Power: 0.75mW/channel
Input-Referred Noise: 4μVPP (150Hz BW, G = 6)
Input Bias Current: 200pA
Data Rate: 250SPS to 32kSPS
CMRR: –115dB
Programmable Gain: 1, 2, 3, 4, 6, 8, or 12
Supports AAMI EC11, EC13, IEC60601-1,
IEC60601-2-27, and IEC60601-2-51 Standards
Unipolar or Bipolar Supplies:
AVDD = 2.7V to 5.25V, DVDD = 1.65V to 3.6V
Built-In Right Leg Drive Amplifier, Lead-Off
Detection, WCT, PACE Detection, Test Signals
Integrated Respiration Impedance
Measurement (ADS1294R/6R/8R only)
Digital PACE Detection Capability
Built-In Oscillator and Reference
Flexible Power-Down, Standby Modes
SPI™-Compatible Serial Interface
Operating Temperature Range:
–40°C to +85°C
APPLICATIONS
•
Package options include a tiny 8mm × 8mm, 64-ball
BGA and a TQFP-64. The ADS1294/6/8 BGA version
is specified over the commercial temperature range of
0°C to +70°C. The ADS1294R/6R/8R BGA and
ADS1294/6/8 TQFP versions are specified over the
industrial temperature range of –40°C to +85°C.
REF
Test Signals and
Monitors
Reference
ADS129xR
RESP
DEMOD
A1
SPI
ADC1
A2
ADC2
A3
ADC3
A4
ADC4
A5
ADC5
A6
ADC6
A7
ADC7
Oscillator
MUX
Control
GPIO AND CONTROL
The ADS1294/6/8/4R/6R/8R are a family of
multichannel,
simultaneous
sampling,
24-bit,
delta-sigma (ΔΣ) analog-to-digital converters (ADCs)
with built-in programmable gain amplifiers (PGAs),
internal reference, and an onboard oscillator. The
ADS1294/6/8/4R/6R/8R incorporate all of the features
that
are
commonly
required
in
medical
electrocardiogram (ECG) and electroencephalogram
(EEG) applications.
Multiple ADS1294/6/8/4R/6R/8R devices can be
cascaded in high channel count systems in a
daisy-chain configuration.
CLK
DESCRIPTION
The ADS1294/6/8/4R/6R/8R have a flexible input
multiplexer per channel that can be independently
connected to the internally-generated signals for test,
temperature, and lead-off detection. Additionally, any
configuration of input channels can be selected for
derivation of the right leg drive (RLD) output signal.
The ADS1294/6/8/4R/6R/8R operate at data rates as
high as 32kSPS, thereby allowing the implementation
of software PACE detection. Lead-off detection can
be implemented internal to the device, either with a
pull-up/pull-down resistor or an excitation current
sink/source. Three integrated amplifiers generate the
Wilson Central Terminal (WCT) and the Goldberger
Central Terminals (GCT) required for a standard
12-lead ECG. The ADS1294R/6R/8R versions
include a fully-integrated, respiration impedance
measurement function.
SPI
•
Medical Instrumentation (ECG, EMG and EEG):
Patient monitoring; Holter, event, stress, and
vital signs including ECG, AED, telemedicine
Bispectral index (BIS), Evoked audio potential
(EAP), Sleep study monitor
High-Precision, Simultaneous, Multichannel
Signal Acquisition
With its high levels of integration and exceptional
performance, the ADS1294/6/8/4R/6R/8R family
enables the development of scalable medical
instrumentation systems at significantly reduced size,
power, and overall cost.
INPUTS
FEATURES
1
ADC8
A8
To Channel
WCT
RESP
Wilson
Terminal
¼
¼
Resp
¼
ADS129xR
RLD
PACE
1
2
3
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of Texas
Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
SPI is a trademark of Motorola.
All other trademarks are the property of their respective owners.
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of the Texas
Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.
Copyright © 2010–2012, Texas Instruments Incorporated
ADS1294, ADS1294R
ADS1296, ADS1296R
ADS1298, ADS1298R
SBAS459I – JANUARY 2010 – REVISED JANUARY 2012
www.ti.com
This integrated circuit can be damaged by ESD. Texas Instruments recommends that all integrated circuits be handled with
appropriate precautions. Failure to observe proper handling and installation procedures can cause damage.
ESD damage can range from subtle performance degradation to complete device failure. Precision integrated circuits may be more
susceptible to damage because very small parametric changes could cause the device not to meet its published specifications.
FAMILY AND ORDERING INFORMATION (1)
PRODUCT
PACKAGE
OPTION
NUMBER OF
CHANNELS
ADC
RESOLUTION
MAXIMUM
SAMPLE RATE
(kSPS)
OPERATING
TEMPERATURE
RANGE
RESPIRATION
CIRCUITRY
BGA
4
16
8
0°C to +70°C
No
TQFP
4
16
8
0°C to +70°C
No
BGA
6
16
8
0°C to +70°C
No
TQFP
6
16
8
0°C to +70°C
No
BGA
8
16
8
0°C to +70°C
No
TQFP
8
16
8
0°C to +70°C
No
BGA
4
24
32
0°C to +70°C
External
ADS1294R
BGA
4
24
32
–40°C to +85°C
Yes
ADS1294
TQFP
4
24
32
–40°C to +85°C
External
ADS1296
BGA
6
24
32
0°C to +70°C
External
ADS1296R
BGA
6
24
32
–40°C to +85°C
Yes
ADS1296
TQFP
6
24
32
–40°C to +85°C
External
ADS1298
BGA
8
24
32
0°C to +70°C
External
ADS1298R
BGA
8
24
32
–40°C to +85°C
Yes
ADS1298
TQFP
8
24
32
–40°C to +85°C
External
ADS1194
ADS1196
ADS1198
ADS1294
(1)
For the most current package and ordering information, see the Package Option Addendum at the end of this document, or visit the
device product folder at www.ti.com.
ABSOLUTE MAXIMUM RATINGS (1)
Over operating free-air temperature range, unless otherwise noted.
ADS1294, ADS1296, ADS1298
ADS1294R, ADS1296R, ADS1298R
UNIT
AVDD to AVSS
–0.3 to +5.5
V
DVDD to DGND
–0.3 to +3.9
V
AVSS to DGND
–3 to +0.2
V
VREF input to AVSS
AVSS – 0.3 to AVDD + 0.3
V
Analog input to AVSS
AVSS – 0.3 to AVDD + 0.3
V
Digital input voltage to DGND
–0.3 to DVDD + 0.3
V
Digital output voltage to DGND
–0.3 to DVDD + 0.3
V
Input current (momentary)
100
mA
Input current (continuous)
10
mA
Commerical Grade: ADS1294, ADS1296, ADS1298
0 to +70
°C
Industrial grade: ADS1294I, ADS1296I, ADS1298I,
ADS1294RI, ADS1296RI, ADS1298RI
–40 to +85
°C
Human body model (HBM)
JEDEC standard 22, test method A114-C.01, all pins
±2000
V
Charged device model (CDM)
JEDEC standard 22, test method C101, all pins
±500
V
–60 to +150
°C
+150
°C
Operating
temperature
range
ESD ratings
Storage temperature range
Maximum junction temperature (TJ)
(1)
2
Stresses above these ratings may cause permanent damage. Exposure to absolute maximum conditions for extended periods may
degrade device reliability. These are stress ratings only, and functional operation of the device at these or any other conditions beyond
those specified is not implied.
Submit Documentation Feedback
Copyright © 2010–2012, Texas Instruments Incorporated
Product Folder Link(s): ADS1294 ADS1294R ADS1296 ADS1296R ADS1298 ADS1298R
ADS1294, ADS1294R
ADS1296, ADS1296R
ADS1298, ADS1298R
SBAS459I – JANUARY 2010 – REVISED JANUARY 2012
www.ti.com
ELECTRICAL CHARACTERISTICS
Minimum/maximum specifications apply for all commercial grade (0°C to +70°C) devices and from –40°C to +85°C for
industrial grades devices. Typical specifications are at +25°C. All specifications at DVDD = 1.8V, AVDD – AVSS = 3V (1),
VREF = 2.4V, external fCLK = 2.048MHz, data rate = 500SPS, High-Resolution mode, and gain = 6, unless otherwise noted.
ADS1294, ADS1296, ADS1298
ADS1294R, ADS1296R, ADS1298R
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
ANALOG INPUTS
Full-scale differential input voltage (AINP – AINN)
±VREF/GAIN
V
See the Input Common-Mode Range
subsection of the PGA Settings and Input
Range section
Input common-mode range
Input capacitance
20
pF
±200
TA = +25°C, input = 1.5V
Input bias current
±1
TA = 0°C to +70°C, input = 1.5V
TA = –40°C to +85°C, input = 1.5V
No lead-off
DC input impedance
pA
nA
±1.2
nA
1000
MΩ
Current source lead-off detection
500
MΩ
Pull-up resistor lead-off detection
10
MΩ
PGA PERFORMANCE
Gain settings
1, 2, 3, 4, 6, 8, 12
Bandwidth
See Table 6
ADC PERFORMANCE
Resolution
Data rate
Data rates up to 8kSPS, no missing codes
24
Bits
16kSPS data rate
19
Bits
32kSPS data rate
17
Bits
fCLK = 2.048MHz, High-Resolution mode
500
32000
SPS
fCLK = 2.048MHz, Low-Power mode
250
16000
SPS
CHANNEL PERFORMANCE
DC Performance
Input-referred noise
Gain = 6 (2), 10 seconds of data
5
Gain = 6, 256 points, 0.5 seconds of data
4
Gain settings other than 6, data rates other
than 500SPS
Integral nonlinearity
μVPP
See Noise Measurements section
Full-scale with gain = 6, best fit
8
ppm
Full-scale with gain = 6, best fit,
ADS1294R/6R/8R channel 1
40
ppm
–20dBFS with gain = 6, best fit,
ADS1294R/6R/8R channel 1
8
ppm
±500
Offset error
Offset error drift
µV
µV/°C
2
Gain error
Excluding voltage reference error
Gain drift
Excluding voltage reference drift
Gain match between channels
(1)
(2)
μVPP
7
±0.2
±0.5
% of FS
5
ppm/°C
0.3
% of FS
Performance is applicable for 5V operation as well. Production testing for limits is performed at 3V.
Noise data measured in a 10-second interval. Test not performed in production. Input-referred noise is calculated with input shorted
(without electrode resistance) over a 10-second interval.
Copyright © 2010–2012, Texas Instruments Incorporated
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3
ADS1294, ADS1294R
ADS1296, ADS1296R
ADS1298, ADS1298R
SBAS459I – JANUARY 2010 – REVISED JANUARY 2012
www.ti.com
ELECTRICAL CHARACTERISTICS (continued)
Minimum/maximum specifications apply for all commercial grade (0°C to +70°C) devices and from –40°C to +85°C for
industrial grades devices. Typical specifications are at +25°C. All specifications at DVDD = 1.8V, AVDD – AVSS = 3V(1),
VREF = 2.4V, external fCLK = 2.048MHz, data rate = 500SPS, High-Resolution mode, and gain = 6, unless otherwise noted.
ADS1294, ADS1296, ADS1298
ADS1294R, ADS1296R, ADS1298R
PARAMETER
TEST CONDITIONS
MIN
TYP
–105
MAX
UNIT
CHANNEL PERFORMANCE (continued)
AC Performance
Common-mode rejection ratio (CMRR)
fCM = 50Hz, 60Hz (3)
–115
dB
Power-supply rejection ratio (PSRR)
fPS = 50Hz, 60Hz
90
dB
Crosstalk
fIN = 50Hz, 60Hz
–126
dB
Signal-to-noise ratio (SNR)
fIN = 10Hz input, gain = 6
112
dB
10Hz, –0.5dBFs
–98
dB
ADS1294R/6R/8R channel 1, 10Hz, –0.5dBFs
–70
dB
–100
dB
ADS1294R/6R/8R channel 1,
100Hz, –0.5dBFs (4)
–68
dB
ADS1294R/6R/8R channel 1,
100Hz, –20dBFs (4)
–86
dB
100Hz, –0.5dBFs (4)
Total harmonic distortion (THD)
DIGITAL FILTER
–3dB bandwidth
0.262fDR
Digital filter settling
Full setting
Hz
4
Conversions
RIGHT LEG DRIVE (RLD) AMPLIFIER AND PACE AMPLIFIERS
RLD integrated noise
BW = 150Hz
7
μVRMS
PACE integrated noise
BW = 8kHz
20
µVRMS
PACE amplifier crosstalk
Crosstalk between PACE amplifiers
60
dB
Gain bandwidth product
50kΩ || 10pF load, gain = 1
100
kHz
Slew rate
50kΩ || 10pF load, gain = 1
0.25
V/μs
Short-circuit to GND (AVDD = 3V)
270
μA
Short-circuit to supply (AVDD = 3V)
550
μA
Short-circuit to GND (AVDD = 5V)
490
μA
Short-circuit to supply (AVDD = 5V)
810
μA
Peak swing (AVSS + 0.3V to AVDD + 0.3V)
at AVDD = 3V
50
μA
Peak swing (AVSS + 0.3V to AVDD + 0.3V)
at AVDD = 5V
75
μA
PACE and RLD amplifier drive strength
PACE and RLD current
PACE amplifier output resistance
Total harmonic distortion
fIN = 100Hz, gain = 1
Common-mode input range
Common-mode resistor matching
Ω
–70
dB
AVDD – 0.3
AVSS + 0.7
Internal 200kΩ resistor matching
Short-circuit current
Quiescent power consumption
100
Either RLD or PACE amplifier
V
0.1
%
±0.25
mA
20
μA
WILSON CENTRAL TERMINAL (WCT) AMPLIFIER
Integrated noise
See Table 5
nV/√Hz
Gain bandwidth product
BW = 150Hz
See Table 5
kHz
Slew rate
See Table 5
V/s
Total harmonic distortion
fIN = 100Hz
Common-mode input range
Short-circuit current
(3)
(4)
4
dB
AVDD – 0.3
AVSS + 0.3
Through internal 30kΩ resistor
Quiescent power consumption
90
V
±0.25
mA
See Table 5
μA
CMRR is measured with a common-mode signal of AVSS + 0.3V to AVDD – 0.3V. The values indicated are the maximum of the eight
channels.
Harmonics above the second harmonic are attenuated by the digital filter.
Submit Documentation Feedback
Copyright © 2010–2012, Texas Instruments Incorporated
Product Folder Link(s): ADS1294 ADS1294R ADS1296 ADS1296R ADS1298 ADS1298R
ADS1294, ADS1294R
ADS1296, ADS1296R
ADS1298, ADS1298R
SBAS459I – JANUARY 2010 – REVISED JANUARY 2012
www.ti.com
ELECTRICAL CHARACTERISTICS (continued)
Minimum/maximum specifications apply for all commercial grade (0°C to +70°C) devices and from –40°C to +85°C for
industrial grades devices. Typical specifications are at +25°C. All specifications at DVDD = 1.8V, AVDD – AVSS = 3V(1),
VREF = 2.4V, external fCLK = 2.048MHz, data rate = 500SPS, High-Resolution mode, and gain = 6, unless otherwise noted.
ADS1294, ADS1296, ADS1298
ADS1294R, ADS1296R, ADS1298R
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
LEAD-OFF DETECT
Frequency
See the Register Map section for settings
0, fDR/4
kHz
Current
See the Register Map section for settings
6, 12, 18, 24
nA
Current accuracy
±20
%
Comparator threshold accuracy
±30
mV
RESPIRATION (ADS1294R/6R/8R Only)
Internal source
Frequency
External source
32, 64
32
kHz
64
22.5
90
157.5
kHz
Phase shift
See the Register Map section for settings
Impedance range
IRESP = 30μA
Impedance measurement noise
0.05Hz to 2Hz brick wall filter, 32kHz
modulation clock, phase = 112.5,
using IRESP = 30μA with 2kΩ baseline load,
gain = 4 test condition
20
mΩPP
Modulator current
internal reference, signal path = 82kΩ,
baseline = 2.21kΩ
29
µA
3V supply VREF = (VREFP – VREFN)
2.5
V
5V supply VREF = (VREFP – VREFN)
4.0
V
AVSS
V
10
Degrees
kΩ
EXTERNAL REFERENCE
Reference input voltage
Negative input (VREFN)
Positive input (VREFP)
AVSS + 2.5
Input impedance
V
10
kΩ
Register bit CONFIG3.VREF_4V = 0,
AVDD ≥ 2.7V
2.4
V
Register bit CONFIG3.VREF_4V = 1,
AVDD ≥ 4.4V
4.0
V
INTERNAL REFERENCE
Output voltage
±0.2
VREF accuracy
%
TA = +25°C
35
ppm/°C
Commerical grade, 0°C to +70°C
35
ppm
Industrial grade, –40°C to +85°C
45
ppm
150
ms
Analog supply reading error
2
%
Digital supply reading error
2
%
150
ms
Internal reference drift
Start-up time
SYSTEM MONITORS
From power-up to DRDY low
Device wake up
STANDBY mode
Temperature sensor reading, voltage
TA = +25°C
Temperature sensor reading, coefficient
9
ms
145
mV
490
μV/°C
Test Signal
Signal frequency
See Register Map section for settings
fCLK/221, fCLK/220
Hz
Signal voltage
See Register Map section for settings
±1, ±2
mV
±2
Accuracy
Copyright © 2010–2012, Texas Instruments Incorporated
%
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Product Folder Link(s): ADS1294 ADS1294R ADS1296 ADS1296R ADS1298 ADS1298R
5
ADS1294, ADS1294R
ADS1296, ADS1296R
ADS1298, ADS1298R
SBAS459I – JANUARY 2010 – REVISED JANUARY 2012
www.ti.com
ELECTRICAL CHARACTERISTICS (continued)
Minimum/maximum specifications apply for all commercial grade (0°C to +70°C) devices and from –40°C to +85°C for
industrial grades devices. Typical specifications are at +25°C. All specifications at DVDD = 1.8V, AVDD – AVSS = 3V(1),
VREF = 2.4V, external fCLK = 2.048MHz, data rate = 500SPS, High-Resolution mode, and gain = 6, unless otherwise noted.
ADS1294, ADS1296, ADS1298
ADS1294R, ADS1296R, ADS1298R
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
CLOCK
Internal oscillator clock frequency
Nominal frequency
2.048
MHz
TA = +25°C
0°C ≤ TA ≤ +70°C
Internal clock accuracy
–40°C ≤ TA ≤ +85°C,
ADS1298I industrial grade version only
Internal oscillator start-up time
%
±2
%
±2.5
%
20
Internal oscillator power consumption
External clock input frequency
±0.5
CLKSEL pin = 0
1.94
μs
μW
120
2.048
2.25
MHz
DIGITAL INPUT/OUTPUT (DVDD = 1.65V to 3.6V)
Logic level
VIH
0.8DVDD
DVDD + 0.1
V
VIL
–0.1
0.2DVDD
V
VOH
IOH = –500μA
VOL
IOL = +500μA
Input current (IIN)
0V < VDigitalInput < DVDD
DVDD – 0.4
V
–10
0.4
V
+10
μA
POWER-SUPPLY REQUIREMENTS
Analog supply (AVDD – AVSS)
2.7
3.0
5.25
V
Digital supply (DVDD)
1.65
1.8
3.6
V
AVDD – DVDD
–2.1
3.6
V
SUPPLY CURRENT (RLD, WCT, and PACE Amplifiers Turned Off)
High-Resolution mode (ADS1298)
IAVDD
IDVDD
AVDD – AVSS = 3V
2.75
mA
AVDD – AVSS = 5V
3.1
mA
DVDD = 3.0V
0.5
mA
DVDD = 1.8V
0.3
mA
AVDD – AVSS = 3V
1.8
mA
AVDD – AVSS = 5V
2.1
mA
DVDD = 3.0V
0.5
mA
DVDD = 1.8V
0.3
mA
Low-Power mode (ADS1298)
IAVDD
IDVDD
POWER DISSIPATION (Analog Supply = 3V, RLD, WCT, and PACE Amplifiers Turned Off)
Quiescent power dissipation
ADS1298/8R
ADS1296/6R
ADS1294/4R
High-Resolution mode
8.8
9.5
mW
Low-Power mode (250SPS)
6.0
7.0
mW
High-Resolution mode
7.2
7.9
mW
Low-Power mode
5.3
6.6
mW
High-Resolution mode
5.4
6
mW
Low-Power mode
4.1
4.4
mW
Power-down
Standby mode
Quiescent channel power
6
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PGA + ADC
10
μW
2
mW
818
μW
Copyright © 2010–2012, Texas Instruments Incorporated
Product Folder Link(s): ADS1294 ADS1294R ADS1296 ADS1296R ADS1298 ADS1298R
ADS1294, ADS1294R
ADS1296, ADS1296R
ADS1298, ADS1298R
SBAS459I – JANUARY 2010 – REVISED JANUARY 2012
www.ti.com
ELECTRICAL CHARACTERISTICS (continued)
Minimum/maximum specifications apply for all commercial grade (0°C to +70°C) devices and from –40°C to +85°C for
industrial grades devices. Typical specifications are at +25°C. All specifications at DVDD = 1.8V, AVDD – AVSS = 3V(1),
VREF = 2.4V, external fCLK = 2.048MHz, data rate = 500SPS, High-Resolution mode, and gain = 6, unless otherwise noted.
ADS1294, ADS1296, ADS1298
ADS1294R, ADS1296R, ADS1298R
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
POWER DISSIPATION (Analog Supply = 5V, RLD, WCT, and PACE Amplifiers Turned Off)
Quiescent power dissipation
ADS1298/8R
ADS1296/6R
High-Resolution mode
17.5
mW
Low-Power mode
12.5
mW
High-Resolution mode
14.1
mW
10
mW
10.1
mW
8.3
mW
Low-Power mode
High-Resolution mode
ADS1294/4R
Low-Power mode
Power-down
Standby mode
Quiescent channel power
PGA + ADC
20
μW
4
mW
1.5
mW
TEMPERATURE
Specified temperature range
0
+70
°C
Operating temperature range
0
+70
°C
Specified temperature range
(industrial grade only)
–40
+85
°C
Operating temperature range
(industrial grade only)
–40
+85
°C
Storage temperature range
–60
+150
°C
THERMAL INFORMATION
THERMAL METRIC
ADS1294/6/8
ADS1294/6/8/
4R/6R/8R
PAG
ZXG
(1)
64 PINS
64 PINS
θJA
Junction-to-ambient thermal resistance
35
48
θJCtop
Junction-to-case (top) thermal resistance
31
8
θJB
Junction-to-board thermal resistance
26
25
ψJT
Junction-to-top characterization parameter
0.1
0.5
ψJB
Junction-to-board characterization parameter
—
22
θJCbot
Junction-to-case (bottom) thermal resistance
—
—
(1)
UNITS
°C/W
For more information about traditional and new thermal metrics, see the IC Package Thermal Metrics application report, SPRA953.
Copyright © 2010–2012, Texas Instruments Incorporated
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Product Folder Link(s): ADS1294 ADS1294R ADS1296 ADS1296R ADS1298 ADS1298R
7
ADS1294, ADS1294R
ADS1296, ADS1296R
ADS1298, ADS1298R
SBAS459I – JANUARY 2010 – REVISED JANUARY 2012
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NOISE MEASUREMENTS
NOTE
The ADS1294R/6R/8R channel performance differs from the ADS1294/6/8 in regards to
respiration circuitry found on channel one. Unless otherwise noted, ADS129x refers to all
specifications and functional descriptions of the ADS1294, ADS1296, ADS1298,
ADS1294R, ADS1296R, and ADS1298R.
The ADS129x noise performance can be optimized by adjusting the data rate and PGA setting. As the averaging
is increased by reducing the data rate, the noise drops correspondingly. Increasing the PGA value reduces the
input-referred noise, which is particularly useful when measuring low-level biopotential signals. Table 1 and
Table 2 summarize the noise performance of the ADS129x in the High-Resolution (HR) mode and Low-Power
(LP) mode, respectively, with a 3V analog power supply. Table 3 and Table 4 summarize the noise performance
of the ADS129x in the HR mode and LP mode, respectively, with a 5V analog power supply. The data are
representative of typical noise performance at TA = +25°C. The data shown are the result of averaging the
readings from multiple devices and are measured with the inputs shorted together. A minimum of 1000
consecutive readings are used to calculate the RMS and peak-to-peak noise for each reading. For the two
highest data rates, the noise is limited by quantization noise of the ADC and does not have a gaussian
distribution. Thus, the ratio between rms noise and peak-to-peak noise is approximately 10. For the lower data
rates, the ratio is approximately 6.6.
Table 1 to Table 4 show measurements taken with an internal reference. The data are also representative of the
ADS129x noise performance when using a low-noise external reference such as the REF5025.
Table 1. Input-Referred Noise (μVRMS/μVPP) in High-Resolution Mode
3V Analog Supply and 2.4V Reference (1)
DR BITS OF
CONFIG1
REGISTER
OUTPUT
DATA RATE
(SPS)
–3dB
BANDWIDTH
(Hz)
PGA
GAIN = 1
PGA
GAIN = 2
PGA
GAIN = 3
000
32000
8398
335/3553
168/1701
001
16000
4193
56/613
28/295
010
8000
2096
12.4/111
011
4000
1048
100
2000
101
110
(1)
PGA
GAIN = 4
PGA
GAIN = 6
PGA
GAIN = 8
PGA
GAIN = 12
112/1100
85/823
58/529
42.5/378
28.6/248
18.8/188
14.3/143
9.7/94
7.4/69
5.2/44.3
6.5/54
4.5/37.9
3.5/29.7
2.6/21.7
2.2/17.8
1.8/13.8
6.1/44.8
3.2/23.3
2.4/17.1
1.9/14.0
1.5/11.1
1.3/9.7
1.2/8.5
524
4.1/27.8
2.2/15.4
1.6/11.0
1.3/9.1
1.1/7.3
1.0/6.5
0.9/6.0
1000
262
2.9/19.0
1.6/10.1
1.2/7.5
1.0/6.2
0.8/5.0
0.7/4.6
0.6/4.1
500
131
2.1/12.5
1.1/6.8
0.9/5.1
0.7/4.3
0.6/3.5
0.5/3.1
0.5/2.9
PGA
GAIN = 12
At least 1000 consecutive readings were used to calculate the RMS and peak-to-peak noise values in this table.
Table 2. Input-Referred Noise (μVRMS/μVPP) in Low-Power Mode
3V Analog Supply and 2.4V Reference (1)
DR BITS OF
CONFIG1
REGISTER
OUTPUT
DATA RATE
(SPS)
–3dB
BANDWIDTH
(Hz)
PGA
GAIN = 1
PGA
GAIN = 2
PGA
GAIN = 3
000
16000
4193
333/3481
166/1836
001
8000
2096
56/554
28/272
010
4000
1048
12.5/99
011
2000
524
6.1/41.8
100
1000
262
4.1/26.3
101
500
131
110
250
65
(1)
8
PGA
GAIN = 4
PGA
GAIN = 6
PGA
GAIN = 8
111/1168
84/834
56/576
42/450
28/284
19/177
14.3/133
9.7/85
7.4/64
5.0/42.4
6.5/51
4.5/35.0
3.4/25.9
2.4/18.8
2.0/14.5
1.5/11.3
3.2/22.2
2.3/15.9
1.8/12.1
1.4/9.3
1.2/7.8
1.0/6.7
2.2/14.6
1.6/9.9
1.3/8.1
1.0/6.2
0.8/5.4
0.7/4.7
3.0/17.9
1.6/9.8
1.1/6.8
0.9/5.7
0.7/4.2
0.6/3.6
0.5/3.4
2.1/11.9
1.1/6.3
0.8/4.6
0.7/4.0
0.5/3.0
0.5/2.6
0.4/2.4
At least 1000 consecutive readings were used to calculate the RMS and peak-to-peak noise values in this table.
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Table 3. Input-Referred Noise (μVRMS/μVPP) in High-Resolution Mode
5V Analog Supply and 4V Reference (1)
DR BITS OF
CONFIG1
REGISTER
OUTPUT
DATA RATE
(SPS)
–3dB
BANDWIDTH
(Hz)
PGA
GAIN = 1
PGA
GAIN = 2
PGA
GAIN = 3
PGA
GAIN = 4
PGA
GAIN = 6
PGA
GAIN = 8
PGA
GAIN = 12
000
32000
8398
521/5388
260/2900
173/1946
130/1403
87/917
65/692
44/483
001
16000
4193
86/1252
43/633
29/402
22/298
15/206
11/141
7/91
010
8000
2096
17/207
9/112
6/71
4/57
3/36
3/29
2/18
011
4000
1048
6.4/48.2
3.4/25.9
2.417.7
1.9/15.4
1.5/11.2
1.3/9.6
1.1/8.2
100
2000
524
4.2/29.9
2.3/15.9
1.6/11.1
1.3/9.3
1.0/7.5
0.9/6.6
0.8/5.8
101
1000
262
2.9/18.8
1.6/10.4
1.1/7.8
0.9/6.1
0.7/4.9
0.6/4.7
0.6/3.9
110
500
131
2.0/12.8
1.1/7.2
0.8/5.2
0.7/4.0
0.5/3.3
0.5/3.3
0.4/2.7
(1)
At least 1000 consecutive readings were used to calculate the RMS and peak-to-peak noise values in this table.
Table 4. Input-Referred Noise (μVRMS/μVPP) in Low-Power Mode
5V Analog Supply and 4V Reference (1)
DR BITS OF
CONFIG1
REGISTER
OUTPUT
DATA RATE
(SPS)
–3dB
BANDWIDTH
(Hz)
PGA
GAIN = 1
PGA
GAIN = 2
PGA
GAIN = 3
PGA
GAIN = 4
PGA
GAIN = 6
PGA
GAIN = 8
PGA
GAIN = 12
000
16000
4193
526/5985
263/2953
175/1918
132/1410
88/896
66/681
44/458
001
8000
2096
88/1201
44/619
29/411
22/280
15/191
11/139
7/83
010
4000
1048
17/208
9/103
6/62
4/52
3/37
2/25
2/16
011
2000
524
6.0/41.1
3.3/23.3
2.2/15.5
1.8/12.3
1.3/9.8
1.1/7.8
0.9/6.5
100
1000
262
4.1/27.1
2.3/14.8
1.5/10.1
1.2/8.1
0.9/6.0
0.8/5.4
0.7/4.4
101
500
131
2.9/17.4
1.6/9.6
1.1/6.6
0.9/5.9
0.7/4.3
0.6/3.4
0.5/3.2
110
250
65
2.1/11.9
1.1/6.6
0.8/4.6
0.6/3.7
0.5/3.0
0.4/2.5
0.4/2.2
(1)
At least 1000 consecutive readings were used to calculate the RMS and peak-to-peak noise values in this table.
Table 5. Typical WCT Performance
PARAMETER
ANY ONE
(A, B, or C)
ANY TWO
(A+B, A+C, or B+C)
ALL THREE
(A+B+C)
UNIT
Integrated noise
540
382
312
nVRMS
Power
53
59
65
μW
–3dB BW
30
59
89
kHz
Slew rate
BW limited
BW limited
BW limited
—
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PIN CONFIGURATIONS
ZXG PACKAGE
BGA-64
(TOP VIEW, SOLDER BUMPS ON BOTTOM SIDE)
H
G
F
E
D
C
B
A
IN1P
IN2P
IN3P
IN4P
IN5P
IN6P
IN7P
IN8P
1
IN1N
IN2N
IN3N
IN4N
IN5N
IN6N
IN7N
IN8N
2
VREFP
VCAP4
TESTN_
PACE_OUT2
TESTP_
PACE_OUT1
WCT
RLDINV
RLDOUT
RLDIN
3
VREFN
RESP_
MODP
RESP_
MODN
RESV1
AVSS
RLDREF
AVDD
AVDD
4
VCAP1
PWDN
GPIO1
GPIO4
AVSS
AVSS
AVSS
AVSS
5
VCAP2
RESET
DAISY_IN
GPIO3
DRDY
AVDD
AVDD
AVDD
6
DGND
START
GPIO2
CS
DGND
DGND
VCAP3
AVDD1
7
CLK
DIN
SCLK
DOUT
DVDD
DVDD
CLKSEL
AVSS1
8
BGA PIN ASSIGNMENTS
NAME
TERMINAL
FUNCTION
DESCRIPTION
IN8P (1)
1A
Analog input
Differential analog positive input 8 (ADS1298/8R)
IN7P (1)
1B
Analog input
Differential analog positive input 7 (ADS1298/8R)
IN6P (1)
1C
Analog input
Differential analog positive input 6 (ADS1296/8/6R/8R)
(1)
1D
Analog input
Differential analog positive input 5 (ADS1296/8/6R/8R)
IN4P (1)
1E
Analog input
Differential analog positive input 4
IN3P (1)
1F
Analog input
Differential analog positive input 3
IN2P (1)
1G
Analog input
Differential analog positive input 2
IN1P (1)
1H
Analog input
Differential analog positive input 1
IN8N (1)
2A
Analog input
Differential analog negative input 8 (ADS1298/8R)
IN7N (1)
2B
Analog input
Differential analog negative input 7 (ADS1298/8R)
IN6N (1)
2C
Analog input
Differential analog negative input 6 (ADS1296/8/6R/8R)
IN5N (1)
2D
Analog input
Differential analog negative input 5 (ADS1296/8/6R/8R)
IN4N (1)
2E
Analog input
Differential analog negative input 4
IN3N (1)
2F
Analog input
Differential analog negative input 3
IN2N (1)
2G
Analog input
Differential analog negative input 2
IN1N (1)
2H
Analog input
Differential analog negative input 1
IN5P
(1)
Connect unused terminals to AVDD.
10
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BGA PIN ASSIGNMENTS (continued)
NAME
TERMINAL
FUNCTION
DESCRIPTION
RLDIN (2)
3A
Analog input
Right leg drive input to MUX
RLDOUT
3B
Analog output
RLDINV
3C
Analog input/output
WCT
3D
Analog output
TESTP_PACE_OUT1 (2)
3E
Analog input/buffer output
Internal test signal/single-ended buffer output based on register settings
TESTN_PACE_OUT2 (2)
3F
Analog input/output
Internal test signal/single-ended buffer output based on register settings
VCAP4
3G
Analog output
VREFP
3H
Analog input/output
AVDD
4A
Supply
Analog supply
AVDD
4B
Supply
Analog supply
RLDREF
4C
Analog input
(2)
Right leg drive output
Right leg drive inverting input
Wilson Central Terminal output
Analog bypass capacitor
Positive reference voltage
Right leg drive noninverting input
AVSS
4D
Supply
RESV1
4E
Digital input
Analog ground
RESP_MODN
4F
Analog output
ADS1294R/6R/8R: modulation clock for respiration measurement, negative
side.
ADS1294/6/8: leave floating.
RESP_MODP
4G
Analog output
ADS1294R/6R/8R: modulation clock for respiration measurement, positive
side.
ADS1294/6/8: leave floating.
VREFN
4H
Analog input
AVSS
5A
Supply
Analog ground
AVSS
5B
Supply
Analog ground
AVSS
5C
Supply
Analog ground
AVSS
5D
Supply
Analog ground
GPIO4
5E
Digital input/output
GPIO4 in normal mode
GPIO1
5F
Digital input/output
General purpose input/output pin
PWDN
5G
Digital input
Power-down; active low
VCAP1
5H
Analog input/output
Analog bypass capacitor
AVDD
6A
Supply
Analog supply
AVDD
6B
Supply
Analog supply
AVDD
6C
Supply
Analog supply
DRDY
6D
Digital output
Data ready; active low
GPIO3
6E
Digital input/output
GPIO3 in normal mode
DAISY_IN
6F
Digital input
Daisy-chain input; if not used, short to DGND.
RESET
6G
Digital input
System reset; active low
Analog bypass capacitor
Reserved for future use; must tie to logic low (DGND).
Negative reference voltage
VCAP2
6H
—
AVDD1
7A
Supply
VCAP3
7B
—
DGND
7C
Supply
Digital ground
DGND
7D
Supply
Digital ground
GPIO2
7E
Digital input/output
CS
7F
Digital input
SPI chip select; active low
START
7G
Digital input
Start conversion
DGND
7H
Supply
Digital ground
AVSS1
8A
Supply
Analog ground for charge pump
CLKSEL
8B
Digital input
Master clock select
DVDD
8C
Supply
Digital power supply
DVDD
8D
Supply
Digital power supply
DOUT
8E
Digital output
SPI data out
SCLK
8F
Digital input
SPI clock
CLK
8G
Digital input/output
DIN
8H
Digital input
Analog supply for charge pump
Analog bypass capacitor; internally generated AVDD + 1.9V.
General-purpose input/output pin
External Master clock input or internal clock output.
SPI data in
Connect unused terminals to AVDD.
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49 DGND
50 DVDD
51 DGND
52 CLKSEL
53 AVSS1
54 AVDD1
55 VCAP3
56 AVDD
57 AVSS
58 AVSS
59 AVDD
60 RLDREF
61 RLDINV
62 RLDIN
GPIO3
IN6N
5
44
GPIO2
IN6P
6
43
DOUT
IN5N
7
42
GPIO1
IN5P
8
41
DAISY_IN
IN4N
9
40
SCLK
IN4P 10
39
CS
IN3N 11
38
START
IN3P 12
37
CLK
IN2N 13
36
RESET
IN2P 14
35
PWDN
IN1N 15
34
DIN
IN1P 16
33
DGND
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AVSS 32
45
RESV1 31
4
VCAP2 30
IN7P
NC 29
GPIO4
VCAP1 28
46
NC 27
3
VCAP4 26
IN7N
VREFN 25
DRDY
VREFP 24
47
AVSS 23
2
AVDD 22
IN8P
AVDD 21
DVDD
AVSS 20
48
AVDD 19
1
TESTN_PACE_OUT2 18
IN8N
TESTP_PACE_OUT1 17
12
63 RLDOUT
64 WCT
PAG PACKAGE
TQFP-64
(TOP VIEW)
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ADS1298, ADS1298R
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PAG PIN ASSIGNMENTS
NAME
PIN
FUNCTION
DESCRIPTION
IN8N (1)
1
Analog input
Differential analog negative input 8 (ADS1298)
IN8P (1)
2
Analog input
Differential analog positive input 8 (ADS1298)
IN7N (1)
3
Analog input
Differential analog negative input 7 (ADS1298)
IN7P (1)
4
Analog input
Differential analog positive input 7 (ADS1298)
IN6N (1)
5
Analog input
Differential analog negative input 6 (ADS1296/8)
IN6P (1)
6
Analog input
Differential analog positive input 6 (ADS1296/8)
IN5N (1)
7
Analog input
Differential analog negative input 5 (ADS1296/8)
IN5P (1)
8
Analog input
Differential analog positive input 5 (ADS1296/8)
IN4N
(1)
9
Analog input
Differential analog negative input 4
IN4P (1)
10
Analog input
Differential analog positive input 4
IN3N (1)
11
Analog input
Differential analog negative input 3
IN3P (1)
12
Analog input
Differential analog positive input 3
IN2N (1)
13
Analog input
Differential analog negative input 2
IN2P (1)
14
Analog input
Differential analog positive input 2
IN1N (1)
15
Analog input
Differential analog negative input 1
IN1P (1)
16
Analog input
Differential analog positive input 1
TESTP_PACE_OUT1 (1)
17
Analog input/buffer output
Internal test signal/single-ended buffer output based on register settings
TESTN_PACE_OUT2 (1)
18
Analog input/output
Internal test signal/single-ended buffer output based on register settings
AVDD
19
Supply
Analog supply
AVSS
20
Supply
Analog ground
AVDD
21
Supply
Analog supply
AVDD
22
Supply
Analog supply
AVSS
23
Supply
Analog ground
VREFP
24
Analog input/output
Positive reference voltage
VREFN
25
Analog input
Negative reference voltage
VCAP4
26
Analog output
NC
27
—
No connection
VCAP1
28
—
Analog bypass capacitor
(1)
Analog bypass capacitor
NC
29
—
No connection
VCAP2
30
—
Analog bypass capacitor
RESV1
31
Digital input
AVSS
32
Supply
Analog ground
DGND
33
Supply
Digital ground
DIN
34
Digital input
SPI data in
PWDN
35
Digital input
Power-down; active low
RESET
36
Digital input
System reset; active low
CLK
37
Digital input/output
START
38
Digital input
Start conversion
CS
39
Digital input
SPI chip select; active low
SCLK
40
Digital input
SPI clock
DAISY_IN
41
Digital input
Daisy-chain input; if not used, short to DGND.
GPIO1
42
Digital input/output
DOUT
43
Digital output
GPIO2
44
Digital input/output
General-purpose input/output pin
GPIO3
45
Digital input/output
General-purpose input/output pin
GPIO4
46
Digital input/output
General-purpose input/output pin
DRDY
47
Digital output
DVDD
48
Supply
Digital power supply
DGND
49
Supply
Digital ground
DVDD
50
Supply
Digital power supply
Reserved for future use; must tie to logic low (DGND).
External Master clock input or internal clock output.
General-purpose input/output pin
SPI data out
Data ready; active low
Connect unused terminals to AVDD.
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PAG PIN ASSIGNMENTS (continued)
NAME
PIN
FUNCTION
DGND
51
Supply
CLKSEL
52
Digital input
AVSS1
53
Supply
Analog ground
AVDD1
54
Supply
Analog supply
VCAP3
55
Analog
Analog bypass capacitor; internally generated AVDD + 1.9V.
AVDD
56
Supply
Analog supply
AVSS
57
Supply
Analog ground
AVSS
58
Supply
Analog ground
AVDD
59
Supply
Analog supply
RLDREF
60
Analog input
RLDINV
61
Analog input/output
Right leg drive inverting input
(1)
62
Analog input
Right leg drive input to MUX
RLDOUT
63
Analog output
Right leg drive output
WCT
64
Analog output
Wilson Central Terminal output
RLDIN
14
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DESCRIPTION
Digital ground
Master clock select
Right leg drive noninverting input
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TIMING CHARACTERISTICS
tCLK
CLK
tCSSC
tSCLK
SCLK
tCSH
tSDECODE
CS
1
tSPWL
tSPWH
3
2
8
1
tDIHD
tDIST
tSCCS
3
2
8
tDOHD
tDOPD
DIN
tCSDOZ
tCSDOD
DOUT
Hi-Z
Hi-Z
NOTE: SPI settings are CPOL = 0 and CPHA = 1.
Figure 1. Serial Interface Timing
tDISCK2ST
MSBD1
DAISY_IN
SCLK
1
2
tDISCK2HT
LSBD1
3
216
218
217
219
tDOPD
DOUT
LSB
MSB
Don’t Care
MSBD1
NOTE: Daisy-chain timing shown for eight-channel ADS1298, ADS1298R, and ADS1298I.
Figure 2. Daisy-Chain Interface Timing
Timing Requirements For Figure 1 and Figure 2
Specifications apply from –40°C to +85°C, unless otherwise noted. Load on DOUT = 20pF || 100kΩ.
2.7V ≤ DVDD ≤ 3.6V
PARAMETER
DESCRIPTION
tCLK
Master clock period
tCSSC
CS low to first SCLK, setup time
MIN
414
TYP
1.65V ≤ DVDD ≤ 2V
MAX
MIN
514
414
TYP
MAX
UNIT
514
ns
6
17
ns
SCLK period
50
66.6
ns
SCLK pulse width, high and low
15
25
ns
tDIST
DIN valid to SCLK falling edge: setup time
10
10
ns
tDIHD
Valid DIN after SCLK falling edge: hold time
10
11
ns
tDOHD
SCLK falling edge to invalid DOUT: hold time
10
10
tDOPD
SCLK rising edge to DOUT valid: setup time
tCSH
CS high pulse
tCSDOD
CS low to DOUT driven
tSCCS
Eighth SCLK falling edge to CS high
tSDECODE
Command decode time
tCSDOZ
CS high to DOUT Hi-Z
tDISCK2ST
DAISY_IN valid to SCLK rising edge: setup time
10
10
ns
tDISCK2HT
DAISY_IN valid after SCLK rising edge: hold time
10
10
ns
tSCLK
tSPWH,
L
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17
ns
32
ns
2
2
10
20
ns
4
4
tCLKs
4
4
tCLKs
10
tCLKs
20
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TYPICAL CHARACTERISTICS
All plots at TA = +25°C, AVDD = 3V, AVSS = 0V, DVDD = 1.8V, internal VREFP = 2.4V, VREFN = AVSS, external clock =
2.048MHz, data rate = 500SPS, High-Resolution mode, and gain = 6, unless otherwise noted.
INPUT-REFERRED NOISE
NOISE HISTOGRAM
1600
1400
2
1200
1
Occurrences
0
-1
1000
800
600
400
-2
200
Peak-to-Peak Over 10sec = 5mV
9
10
Time (sec)
2.18
0
8
1.68
7
1.17
6
0.67
5
0.17
4
-0.34
3
-0.84
2
-1.35
1
-1.85
0
-2.35
-3
-2.88
Input-Referred Noise (mV)
3
Input-Referred Noise (mV)
Figure 3.
Figure 4.
INTERNAL REFERENCE vs TEMPERATURE
CMRR vs FREQUENCY
2.408
Common-Mode Rejection Ratio (dB)
-130
Internal Reference (V)
2.406
2.404
2.402
2.4
2.398
2.396
Gain = 1
Gain = 2
Gain = 3
Gain = 4
Gain = 6
Gain = 8
Gain = 12
-125
-120
-115
-110
-105
-100
-95
Data Rate = 4kSPS
AIN = AVDD - 0.3V to AVSS + 0.3V
-90
-85
-40
35
10
-15
60
10
85
Figure 5.
Figure 6.
LEAKAGE CURRENT vs INPUT VOLTAGE
0.18
LEAKAGE CURRENT vs TEMPERATURE
1200
AVDD - AVSS = 5V
PGA = 1
1000
0.14
Leakage Current (pA)
Input Leakage Current (nA)
0.16
1k
100
Frequency (Hz)
Temperature (°C)
0.12
0.10
0.08
0.06
0.04
800
600
400
200
0.02
0
0
0.3
0.8
1.3
1.8
2.3
2.8
Input Voltage (V)
Figure 7.
16
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3.3
3.8
4.3
4.8
-40
-15
10
35
60
85
Temperature (°C)
Figure 8.
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TYPICAL CHARACTERISTICS (continued)
All plots at TA = +25°C, AVDD = 3V, AVSS = 0V, DVDD = 1.8V, internal VREFP = 2.4V, VREFN = AVSS, external clock =
2.048MHz, data rate = 500SPS, High-Resolution mode, and gain = 6, unless otherwise noted.
PSRR vs FREQUENCY
THD vs FREQUENCY
-105
Gain = 2
105
Gain = 8
Total Harmonic Distortion (dB)
Power-Supply Rejection Ratio (dB)
110
Gain = 12
100
95
Gain = 4
Gain = 6
90
Gain = 3
Gain = 2
85
80
Gain = 1
75
-100
Gain = 1
-95
Gain = 3
-90
Gain = 4
-85
Gain = 6
-80
Gain = 8
-75
Data Rate = 4kSPS
AIN = 0.5dBFS
Data Rate = 4kSPS
10
10
1k
100
Frequency (Hz)
Figure 9.
Figure 10.
INL vs TEMPERATURE
8
8
6
Integral Nonlinearity (ppm)
Integral Nonlinearity (ppm)
INL vs PGA GAIN
10
6
4
2
0
Gain = 1
Gain = 2
Gain = 3
Gain = 4
Gain = 6
Gain = 8
Gain = 12
-2
-4
-6
-8
-10
-1.0 -0.8 -0.6 -0.4 -0.2
4
2
0
-2
-40°C
-20°C
0°C
+25°C
+40°C
+60°C
-4
-6
-8
0
1k
100
Frequency (Hz)
0.2
0.4
0.6
0.8
1.0
-1
0
-0.5
0.5
Figure 11.
Figure 12.
THD FFT PLOT
(60Hz Signal)
FFT PLOT
(60Hz Signal)
PGA Gain = 1
THD = -102dB
SNR = 115dB
fDR = 500SPS
fCLK = External Clock
-40
-60
-80
-100
-120
0
1
-40
-60
-80
-100
-120
-140
-140
-160
-160
-180
PGA Gain = 6
THD = -104dB
SNR = 74.5dB
fDR = 32kSPS
-20
Amplitude (dBFS)
0
-20
+70°C
+85°C
Input Range (Normalized to Full-Scale)
Input (Normalized to Full-Scale)
Amplitude (dBFS)
Gain = 12
-70
70
-180
0
50
100
150
200
250
0
2
4
6
8
10
Frequency (Hz)
Frequency (kHz)
Figure 13.
Figure 14.
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12
14
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TYPICAL CHARACTERISTICS (continued)
All plots at TA = +25°C, AVDD = 3V, AVSS = 0V, DVDD = 1.8V, internal VREFP = 2.4V, VREFN = AVSS, external clock =
2.048MHz, data rate = 500SPS, High-Resolution mode, and gain = 6, unless otherwise noted.
OFFSET vs PGA GAIN
(ABSOLUTE VALUE)
TEST SIGNAL AMPLITUDE ACCURACY
800
70
700
60
Data From 31 Devices, Two Lots
Number of Bins
500
400
300
50
40
30
20
200
10
100
10
12
11
PGA Gain
0.66
9
0.54
8
0.42
7
0.30
6
0.18
5
0.06
4
-0.06
3
-0.18
2
-0.53
1
-0.29
0
0
-0.41
Offset (mV)
600
Error (%)
Figure 15.
Figure 16.
LEAD-OFF COMPARATOR THRESHOLD ACCURACY
LEAD-OFF CURRENT SOURCE ACCURACY
DISTRIBUTION
80
120
Data From 31 Devices, Two Lots
Current Setting = 24nA
Data From 31 Devices, Two Lots
70
100
Number of Bins
Number of Bins
60
50
40
30
80
60
40
20
20
10
0
2.93
2.37
1.80
1.24
0.68
Figure 18.
ADS1294R/6R/8R NONLINEARITY
ADS1298/8R CHANNEL POWER
40
17.5
30
15.5
20
13.5
10
0
Power (mW)
Integral Nonlinearity (ppm)
0.12
Error in Current Magnitude (nA)
Figure 17.
Channel 1
Channel 2
Channel 3
Channel 4
Channel 5
Channel 6
Channel 7
Channel 8
-10
-20
-30
-40
AVDD = 3V
AVDD = 5V
11.5
9.5
7.5
5.5
3.5
1.5
-50
-1
-0.8 -0.6 -0.4 -0.2
0
0.2
0.4
0.6
Input Range (Normalized to Full-Scale)
Figure 19.
18
-0.45
-1.01
-1.57
Threshold Error (mV)
-2.14
-2.70
35
30
25
20
15
10
5
0
-10
-15
-20
0
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0.8
1
0
1
2
3
4
5
6
7
8
Number of Channels Disabled
Figure 20.
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TYPICAL CHARACTERISTICS (continued)
All plots at TA = +25°C, AVDD = 3V, AVSS = 0V, DVDD = 1.8V, internal VREFP = 2.4V, VREFN = AVSS, external clock =
2.048MHz, data rate = 500SPS, High-Resolution mode, and gain = 6, unless otherwise noted.
SNR vs INPUT AMPLITUDE
(10Hz Sine Wave)
ADS129xR THD
120
105
Signal-to-Noise Ratio (dB)
Total Harmonic Distortion (dBc)
110
100
95
90
85
80
75
70
110
100
90
80
Internal Master Clock, AVDD = 3V
Internal Master Clock, AVDD = 5V
External Master Clock, AVDD = 3V
External Master Clock, AVDD = 5V
70
60
65
fIN = 10Hz, -0.5dBFS
50
60
1
2
3
4
5
6
Channel
Figure 21.
Copyright © 2010–2012, Texas Instruments Incorporated
7
8
-60
-50
-40
-30
-20
-12
-5
-2
-0.5
Input Amplitude (dBFS)
Figure 22.
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OVERVIEW
NOTE
The ADS1294R/6R/8R channel performance differs from the ADS1294/6/8 in regards to
respiration circuitry found on channel one. Unless otherwise noted, ADS129x refers to all
specifications and functional descriptions of the ADS1294, ADS1296, ADS1298,
ADS1294R, ADS1296R, and ADS1298R.
The ADS129x are low-power, multichannel, simultaneously-sampling, 24-bit delta-sigma (ΔΣ) analog-to-digital
converters (ADCs) with integrated programmable gain amplifiers (PGAs). These devices integrate various
ECG-specific
functions
that
make them
well-suited for
scalable electrocardiogram
(ECG),
electroencephalography (EEG), and electromyography (EMG) applications. The devices can also be used in
high-performance, multichannel data acquisition systems by powering down the ECG-specific circuitry.
The ADS129x have a highly programmable multiplexer that allows for temperature, supply, input short, and RLD
measurements. Additionally, the multiplexer allows any of the input electrodes to be programmed as the patient
reference drive. The PGA gain can be chosen from one of seven settings (1, 2, 3, 4, 6, 8, and 12). The ADCs in
the device offer data rates from 250SPS to 32kSPS. Communication to the device is accomplished using an
SPI-compatible interface. The device provides four GPIO pins for general use. Multiple devices can be
synchronized using the START pin.
The internal reference can be programmed to either 2.4V or 4V. The internal oscillator generates a 2.048MHz
clock. The versatile right leg drive (RLD) block allows the user to choose the average of any combination of
electrodes to generate the patient drive signal. Lead-off detection can be accomplished either by using a
pull-up/pull-down resistor or a current source/sink. An internal ac lead-off detection feature is also available. The
device supports both hardware PACE detection and software PACE detection. The Wilson Central Terminal
(WCT) block can be used to generate the WCT point of the standard 12-lead ECG.
Additionally, the ADS1294R, ADS1296R, and ADS1298R provide options for an internal respiration modulator
and a demodulator circuit in the signal path of channel 1.
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ADS1296/6R/8/8R
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WCT
IN8N
EMI
Filter
EMI
Filter
EMI
Filter
EMI
Filter
EMI
Filter
EMI
Filter
EMI
Filter
EMI
Filter
AVSS AVSS1
Internal Respiration
Modulator
(ADS129xR)
MUX
WCT
From
Wmuxb
From
Wmuxa
B
A
RLD
Amplifier
PGA8
PGA7
PGA6
PGA5
PGA4
PGA3
PGA2
RLD RLD RLD
IN REF OUT
From
Wmuxc
C
Power-Supply Signal
Lead-Off Excitation Source
PGA1
Temperature Sensor Input
Test Signal
RLD
INV
RESP_DEMOD_EN
RESP
DEMOD
G = 0.4
PACE
OUT2
PACE
Amplifier 2
DS
ADC8
DS
ADC7
DS
ADC6
DS
ADC5
DS
ADC4
DS
ADC3
DS
ADC2
DS
ADC1
Reference
VREFP VREFN
G = 0.4
DGND
RESP
CLK
Oscillator
PACE
OUT1
PACE
Amplifier 1
Control
SPI
DVDD
START
RESET
PWDN
GPIO2
GPIO4/RCLKO
GPIO3/RCLKO
GPIO1
CLK
CLKSEL
CS
SCLK
DIN
DOUT
DRDY
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IN8P
IN7N
IN7P
IN6N
IN6P
IN5N
IN5P
IN4N
IN4P
IN3N
IN3P
IN2N
IN2P
IN1N
IN1P
RESP_MODN
RESP_MODP
AVDD AVDD1
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ADS129xR
ADS1298/8R
ADS129xR
Figure 23. Functional Block Diagram
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THEORY OF OPERATION
This section discusses the details of the ADS129x internal functional elements. The analog blocks are reviewed
first, followed by the digital interface. Blocks implementing ECG-specific functions are covered in the end.
Throughout this document, fCLK denotes the frequency of the signal at the CLK pin, tCLK denotes the period of the
signal at the CLK pin, fDR denotes the output data rate, tDR denotes the time period of the output data, and fMOD
denotes the frequency at which the modulator samples the input.
EMI FILTER
An RC filter at the input acts as an EMI filter on all of the channels. The –3dB filter bandwidth is approximately
3MHz.
INPUT MULTIPLEXER
The ADS129x input multiplexers are very flexible and provide many configurable signal switching options.
Figure 24 shows the multiplexer on a single channel of the device. Note that the device has eight such blocks,
one for each channel. TEST_PACE_OUT1, TEST_PACE_OUT2, and RLD_IN are common to all eight blocks.
VINP and VINN are separate for each of the eight blocks. This flexibility allows for significant device and
sub-system diagnostics, calibration, and configuration. Selection of switch settings for each channel is made by
writing the appropriate values to the CHnSET[2:0] register (see the CHnSET: Individual Channel Settings section
for details) and by writing the RLD_MEAS bit in the CONFIG3 register (see the CONFIG3: Configuration Register
3 subsection of the Register Map section for details). More details of the ECG-specific features of the multiplexer
are presented in the Input Multiplexer subsection of the ECG-Specifc Functions section.
ADS129x
MUX
INT_TEST
TESTP_PACE_OUT1
INT_TEST
MUX[2:0] = 101
TestP
TempP
MvddP
(1)
MUX[2:0] = 100
MUX[2:0] = 011
From LoffP
MUX[2:0] = 000
VINP
MUX[2:0] = 110
EMI
Filter
To PgaP
MUX[2:0] = 010 AND
RLD_MEAS
MUX[2:0] = 001 (AVDD + AVSS)
2
MUX[2:0] = 111
MUX[2:0] = 000
VINN
RLDIN
From LoffN
MUX[2:0] = 001
To PgaN
MUX[2:0] = 010 AND
RLD_MEAS
RLD_REF
MvddN
(1)
TempN
MUX[2:0] = 011
MUX[2:0] = 100
MUX[2:0] = 101
TestN
INT_TEST
TESTN_PACE_OUT2
INT_TEST
(1)
MVDD monitor voltage supply depends on channel number; see the Supply Measurements (MVDDP, MVDDN)
section.
Figure 24. Input Multiplexer Block for One Channel
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Device Noise Measurements
Setting CHnSET[2:0] = 001 sets the common-mode voltage of (AVDD – AVSS)/2 to both inputs of the channel.
This setting can be used to test the inherent noise of the device in the user system.
Test Signals (TestP and TestN)
Setting CHnSET[2:0] = 101 provides internally-generated test signals for use in sub-system verification at
power-up. This functionality allows the entire signal chain to be tested out. Although the test signals are similar to
the CAL signals described in the IEC60601-2-51 specification, this feature is not intended for use in compliance
testing.
Control of the test signals is accomplished through register settings (see the CONFIG2: Configuration Register 2
subsection in the Register Map section for details). TEST_AMP controls the signal amplitude and TEST_FREQ
controls switching at the required frequency.
The test signals are multiplexed and transmitted out of the device at the TESTP_PACE_OUT1 and
TESTN_PACE_OUT2 pins. A bit register (CONFIG2.INT_TEST = 0) deactivates the internal test signals so that
the test signal can be driven externally. This feature allows the calibration of multiple devices with the same
signal. The test signal feature cannot be used in conjunction with the external hardware PACE feature (see the
External Hardware Approach subsection of the ECG-Specific Functions section for details).
Auxiliary Differential Input (TESTP_PACE_OUT1, TESTN_PACE_OUT2)
When hardware PACE detect is not used, the TESTP_PACE_OUT1 and TESPN_PACE_OUT2 signals can be
used as a multiplexed differential input channel. These inputs can be multiplexed to any of the eight channels.
The performance of the differential input signal fed through these pins is identical to the normal channel
performance.
Temperature Sensor (TempP, TempN)
The ADS129x contain an on-chip temperature sensor. This sensor uses two internal diodes with one diode
having a current density 16x that of the other, as shown in Figure 25. The difference in current densities of the
diodes yields a difference in voltage that is proportional to absolute temperature.
As a result of the low thermal resistance of the package to the printed circuit board (PCB), the internal device
temperature tracks the PCB temperature closely. Note that self-heating of the ADS129x causes a higher reading
than the temperature of the surrounding PCB.
The scale factor of Equation 1 converts the temperature reading to °C. Before using this equation, the
temperature reading code must first be scaled to μV.
Temperature (°C) =
Temperature Reading (mV) - 145,300mV
490mV/°C
+ 25°C
(1)
Temperature Sensor Monitor
AVDD
1x
2x
To MUX TempP
To MUX TempN
8x
1x
AVSS
Figure 25. Measurement of the Temperature Sensor in the Input
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Supply Measurements (MVDDP, MVDDN)
Setting CHnSET[2:0] = 011 sets the channel inputs to different supply voltages of the device. For channels 1, 2,
5, 6, 7, and 8, (MVDDP – MVDDN) is [0.5 × (AVDD – AVSS)]; for channel 3 and for channel 4, (MVDDP –
MVDDN) is DVDD/4. Note that to avoid saturating the PGA while measuring power supplies, the gain must be
set to '1'. For example, if AVDD = 2.5V and AVSS = –2.5V, then the measurement result would be 2.5V.
Lead-Off Excitation Signals (LoffP, LoffN)
The lead-off excitation signals are fed into the multiplexer before the switches. The comparators that detect the
lead-off condition are also connected to the multiplexer block before the switches. For a detailed description of
the lead-off block, refer to the Lead-Off Detection subsection in the ECG-Specific Functions section.
Auxiliary Single-Ended Input
The RLD_IN pin is primarily used for routing the right leg drive signal to any of the electrodes in case the right leg
drive electrode falls off. However, the RLD_IN pin can be used as a multiple single-ended input channel. The
signal at the RLD_IN pin can be measured with respect to the voltage at the RLD_REF pin using any of the eight
channels. This measurement is done by setting the channel multiplexer setting to '010' and the RLD_MEAS bit of
the CONFIG3 register to '1'.
ANALOG INPUT
The analog input to the ADS1298 is fully differential. Assuming PGA = 1, the differential input (INP – INN) can
span between –VREF to +VREF. Note that the the absolute range for INP and INN must be between AVSS – 0.3V
and AVDD + 0.3V. Refer to Table 8 for an explanation of the correlation between the analog input and the digital
codes. There are two general methods of driving the analog input of the ADS1298: single-ended or differential,
as shown in Figure 26 and Figure 27. Note that INP and INN are 180°C out-of-phase in the differential input
method. When the input is single-ended, the INN input is held at the common-mode voltage, preferably at
mid-supply. The INP input swings around the same common voltage and the peak-to-peak amplitude is the
(common-mode + 1/2VREF) and the (common-mode – 1/2VREF). When the input is differential, the common-mode
is given by (INP + INN)/2. Both the INP and INN inputs swing from (common-mode + 1/2VREF to
common-mode – 1/2VREF). For optimal performance, it is recommended that the ADS1298 devices be used in a
differential configuration.
-1/2VREF to
+1/2VREF
VREF
peak-to-peak
ADS1298
ADS1298
Common
Voltage
Common
Voltage
Single-Ended Input
VREF
peak-to-peak
Differential Input
Figure 26. Methods of Driving the ADS1298: Single-Ended or Differential
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CM + 1/2VREF
+1/2VREF
INP
CM Voltage
-1/2VREF
INN = CM Voltage
CM - 1/2VREF
t
Single-Ended Inputs
INP
CM + 1/2VREF
+VREF
CM Voltage
CM - 1/2VREF
INN
-VREF
t
Differential Inputs
(INP) + (INN)
, Common-Mode Voltage (Single-Ended Mode) = INN.
2
Input Range (Differential Mode) = (AINP - AINN) = VREF - (-VREF) = 2VREF.
Common-Mode Voltage (Differential Mode) =
Figure 27. Using the ADS1298 in the Single-Ended and Differential Input Modes
PGA SETTINGS AND INPUT RANGE
The PGA is a differential input/differential output amplifier, as shown in Figure 28. It has seven gain settings (1,
2, 3, 4, 6, 8, and 12) that can be set by writing to the CHnSET register (see the CHnSET: Individual Channel
Settings subsection of the Register Map section for details). The ADS129x have CMOS inputs and hence have
negligible current noise. Table 6 shows the typical values of bandwidths for various gain settings. Note that
Table 6 shows the small-signal bandwidth. For large signals, the performance is limited by the slew rate of the
PGA.
From MuxP
PgaP
R2
50kW
R1
20kW
(for Gain = 6)
To ADC
R2
50kW
PgaN
From MuxN
Figure 28. PGA Implementation
Table 6. PGA Gain versus Small-Signal Bandwidth
GAIN
NOMINAL BANDWIDTH AT ROOM
TEMPERATURE (kHz)
1
237
2
146
3
127
4
96
6
64
8
48
12
32
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The resistor string of the PGA that implements the gain has 120kΩ of resistance for a gain of 6. This resistance
provides a current path across the outputs of the PGA in the presence of a differential input signal. This current
is in addition to the quiescent current specified for the device in the presence of a differential signal at the input.
Input Common-Mode Range
The usable input common-mode range of the front end depends on various parameters, including the maximum
differential input signal, supply voltage, PGA gain, etc. This range is described in Equation 2:
AVDD - 0.2 -
Gain VMAX_DIFF
2
> CM > AVSS + 0.2 +
Gain VMAX_DIFF
2
where:
VMAX_DIFF = maximum differential signal at the input of the PGA
CM = common-mode range
(2)
For example:
If VDD = 3V, gain = 6, and VMAX_DIFF = 350mV
Then 1.25V < CM < 1.75V
Input Differential Dynamic Range
The differential (INP – INN) signal range depends on the analog supply and reference used in the system. This
range is shown in Equation 3.
VREF
±VREF 2VREF
Max (INP - INN) <
;
Full-Scale Range =
=
Gain
Gain
Gain
(3)
The 3V supply, with a reference of 2.4V and a gain of 6 for ECGs, is optimized for power with a differential input
signal of approximately 300mV. For higher dynamic range, a 5V supply with a reference of 4V (set by the
VREF_4V bit of the CONFIG3 register) can be used to increase the differential dynamic range.
ADC ΔΣ Modulator
Power Spectral Density (dB)
Each channel of the ADS129x has a 24-bit ΔΣ ADC. This converter uses a second-order modulator optimized for
low-power applications. The modulator samples the input signal at the rate of fMOD = fCLK/4 for High-Resolution
mode and fMOD = fCLK/8 for Low-Power mode. As in the case of any ΔΣ modulator, the noise of the ADS129x is
shaped until fMOD/2, as shown in Figure 29. The on-chip digital decimation filters explained in the next section
can be used to filter out the noise at higher frequencies. These on-chip decimation filters also provide antialias
filtering. This feature of the ΔΣ converters drastically reduces the complexity of the analog antialiasing filters that
are typically needed with Nyquist ADCs.
0
−10
−20
−30
−40
−50
−60
−70
−80
−90
−100
−110
−120
−130
−140
−150
−160
0.001
0.01
0.1
Normalized Frequency (fIN/fMOD)
1
G001
Figure 29. Modulator Noise Spectrum Up To 0.5 × fMOD
26
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DIGITAL DECIMATION FILTER
The digital filter receives the modulator output and decimates the data stream. By adjusting the amount of
filtering, tradeoffs can be made between resolution and data rate: filter more for higher resolution, filter less for
higher data rates. Higher data rates are typically used in ECG applications for implement software PACE
detection and ac lead-off detection.
The digital filter on each channel consists of a third-order sinc filter. The decimation ratio on the sinc filters can
be adjusted by the DR bits in the CONFIG1 register (see the Register Map section for details). This setting is a
global setting that affects all channels and, therefore, in a device all channels operate at the same data rate.
Sinc Filter Stage (sinx/x)
The sinc filter is a variable decimation rate, third-order, low-pass filter. Data are supplied to this section of the
filter from the modulator at the rate of fMOD. The sinc filter attenuates the high-frequency noise of the modulator,
then decimates the data stream into parallel data. The decimation rate affects the overall data rate of the
converter.
Equation 4 shows the scaled Z-domain transfer function of the sinc filter.
½H(z)½ =
1 - Z- N
3
1 - Z- 1
(4)
The frequency domain transfer function of the sinc filter is shown in Equation 5.
sin
½H(f)½ =
N ´ sin
Npf
fMOD
3
pf
fMOD
where:
N = decimation ratio
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(5)
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The sinc filter has notches (or zeroes) that occur at the output data rate and multiples thereof. At these
frequencies, the filter has infinite attenuation. Figure 30 shows the frequency response of the sinc filter and
Figure 31 shows the roll-off of the sinc filter. With a step change at input, the filter takes 3 × tDR to settle. After a
rising edge of the START signal, the filter takes tSETTLE time to give the first data output. The settling time of the
filters at various data rates are discussed in the START subsection of the SPI Interface section. Figure 32 and
Figure 33 show the filter transfer function until fMOD/2 and fMOD/16, respectively, at different data rates. Figure 34
shows the transfer function extended until 4 × fMOD. It can be seen that the passband of the ADS129x repeats
itself at every fMOD. The input R-C anti-aliasing filters in the system should be chosen such that any interference
in frequencies around multiples of fMOD are attenuated sufficiently.
0
0
-20
-0.5
-40
Gain (dB)
Gain (dB)
-1.0
-60
-80
-1.5
-2.0
-100
-2.5
-120
-3.0
-140
0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
0
0.05
0.10
Normalized Frequency (fIN/fDR)
0.15
0.30
0.35
Figure 31. Sinc Filter Roll-Off
0
0
DR[2:0] = 110
DR[2:0] = 110
-20
DR[2:0] = 000
DR[2:0] = 000
-40
Gain (dB)
-40
Gain (dB)
0.25
Normalized Frequency (fIN/fDR)
Figure 30. Sinc Filter Frequency Response
-20
0.20
-60
-80
-60
-80
-100
-100
-120
-120
-140
-140
0
0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50
0
0.01
0.02
Normalized Frequency (fIN/fMOD)
0.04
0.05
0.06
0.07
Normalized Frequency (fIN/fMOD)
Figure 32. Transfer Function of On-Chip
Decimation Filters Until fMOD/2
10
0.03
Figure 33. Transfer Function of On-Chip
Decimation Filters Until fMOD/16
DR[2:0] = 000
DR[2:0] = 110
-10
Gain (dB)
-30
-50
-70
-90
-110
-130
0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
Normalized Frequency (fIN/fMOD)
Figure 34. Transfer Function of On-Chip Decimation Filters
Until 4fMOD for DR[2:0] = 000 and DR[2:0] = 110
28
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REFERENCE
Figure 35 shows a simplified block diagram of the internal reference of the ADS129x. The reference voltage is
generated with respect to AVSS. When using the internal voltage reference, connect VREFN to AVSS.
22mF
VCAP1
R1
(1)
Bandgap
2.4V or 4V
R3
VREFP
(1)
10mF
R2
(1)
VREFN
AVSS
To ADC Reference Inputs
(1) For VREF = 2.4V: R1 = 12.5kΩ, R2 = 25kΩ, and R3 = 25kΩ. For VREF = 4V: R1 = 10.5kΩ, R2 = 15kΩ, and R3 = 35kΩ.
Figure 35. Internal Reference
The external band-limiting capacitors determine the amount of reference noise contribution. For high-end ECG
systems, the capacitor values should be chosen such that the bandwidth is limited to less than 10Hz, so that the
reference noise does not dominate the system noise. When using a 3V analog supply, the internal reference
must be set to 2.4V. In case of a 5V analog supply, the internal reference can be set to 4V by setting the
VREF_4V bit in the CONFIG2 register.
Alternatively, the internal reference buffer can be powered down and VREFP can be applied externally. Figure 36
shows a typical external reference drive circuitry. Power-down is controlled by the PD_REFBUF bit in the
CONFIG3 register. By default the device wakes up in external reference mode.
100kW
10pF
+5V
0.1mF
100W
+5V
VIN
10mF
OUT
22mF
REF5025
TRIM
To VREFP Pin
OPA211
100W
0.1mF
100mF
22mF
Figure 36. External Reference Driver
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CLOCK
The ADS129x provide two different methods for device clocking: internal and external. Internal clocking is ideally
suited for low-power, battery-powered systems. The internal oscillator is trimmed for accuracy at room
temperature. Over the specified temperature range the accuracy varies; see the Electrical Characteristics. Clock
selection is controlled by the CLKSEL pin and the CLK_EN register bit.
The CLKSEL pin selects either the internal or external clock. The CLK_EN bit in the CONFIG1 register enables
and disables the oscillator clock to be output in the CLK pin. A truth table for these two pins is shown in Table 7.
The CLK_EN bit is useful when multiple devices are used in a daisy-chain configuration. It is recommended that
during power-down the external clock be shut down to save power.
Table 7. CLKSEL Pin and CLK_EN Bit
CLKSEL PIN
CONFIG1.CLK_EN
BIT
CLOCK SOURCE
CLK PIN STATUS
0
X
External clock
Input: external clock
1
0
Internal clock oscillator
3-state
1
1
Internal clock oscillator
Output: internal clock oscillator
DATA FORMAT
The ADS129x output 24 bits of data per channel in binary twos complement format, MSB first. The LSB has a
weight of VREF/(223 – 1). A positive full-scale input produces an output code of 7FFFFFh and the negative
full-scale input produces an output code of 800000h. The output clips at these codes for signals exceeding
full-scale. Table 8 summarizes the ideal output codes for different input signals. Note that for DR[2:0] = 000 and
001, the device has only 17 and 19 bits of resolution, respectively. The last seven (in 17-bit mode) or five (in
19-bit mode) bits can be ignored.
Table 8. Ideal Output Code versus Input Signal (1) (2)
INPUT SIGNAL, VIN
(AINP – AINN)
IDEAL OUTPUT CODE (3)
≥ VREF
7FFFFFh
23
– 1)
000001h
0
000000h
–VREF/(223 – 1)
FFFFFFh
≤ –VREF (223/223 – 1)
800000h
+VREF/(2
(1)
(2)
(3)
30
Only valid for 24-bit resolution data rates.
Assumes gain = 1.
Excludes effects of noise, linearity, offset, and gain error.
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SPI INTERFACE
The SPI-compatible serial interface consists of four signals: CS, SCLK, DIN, and DOUT. The interface reads
conversion data, reads and writes registers, and controls the ADS129x operation. The DRDY output is used as a
status signal to indicate when data are ready. DRDY goes low when new data are available.
Chip Select (CS)
Chip select (CS) selects the ADS129x devices for SPI communication. While CS is low the serial interface is
active CS must remain low for the entire duration of the serial communication. After the serial communication is
finished, always wait four or more tCLK cycles before taking CS high. When CS is taken high, the serial interface
is reset, SCLK and DIN are ignored, and DOUT enters a high-impedance state. DRDY asserts when data
conversion is complete, regardless of whether CS is high or low.
While ADS129x is selected the device will attempt to decode and execute commands every eight serial clocks. If
the devices ceases to execute serial commands, it is possible extra clock pulses were presented and placed the
serial interface in an unknown state. Take CS high and back low to reset the serial interface to a known state.
Serial Clock (SCLK)
SCLK is the serial peripheral interface (SPI) serial clock. It is used to shift in commands and shift out data from
the device. The serial clock (SCLK) features a Schmitt-triggered input and clocks data on the DIN and DOUT
pins into and out of the ADS129x. Even though the input has hysteresis, it is recommended to keep SCLK as
clean as possible to prevent glitches from accidentally forcing a clock event. The absolute maximum limit for
SCLK is specified in the Serial Interface Timing table.
While ADS129x is selected(CS = LOW), the device attempts to decode and execute commands every eight
serial clocks. It is therefore recommended that multiples of 8 SCLKs be presented every serial transfer to keep
the interface in a normal operating mode. If the interface ceases to function because of extra serial clocks, it can
be reset by toggling CS high and back to low.
For a single device, the minimum speed needed for the SCLK depends on the number of channels, number of
bits of resolution, and output data rate. (For multiple cascaded devices, see the Cascade Mode subsection of the
Multiple Device Configuration section.)
tSCLK < (tDR – 4tCLK)/(NBITS × NCHANNELS + 24)
(6)
For example, if the ADS1298 is used in a 500SPS mode (eight channels, 24-bit resolution), the minimum SCLK
speed is 110kHz.
Data retrieval can be done either by putting the device in RDATAC mode or by issuing a RDATA command for
data on demand. The above SCLK rate limitation applies to RDATAC. For the RDATA command, the limitation
applies if data must be read between two consecutive DRDY signals. The above calculation assumes that there
are no other commands issued between data captures.
Data Input (DIN)
The data input pin (DIN) is used along with SCLK to communicate with the ADS129x (opcode commands and
register data). The device latches data on DIN on the falling edge of SCLK.
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Data Output (DOUT)
The data output pin (DOUT) is used with SCLK to read conversion and register data from the ADS129x. Data on
DOUT are shifted out on the rising edge of SCLK. DOUT goes to a high-impedance state when CS is high. In
read data continuous mode (see the SPI Command Definitions section for more details), the DOUT output line
also indicates when new data are available. This feature can be used to minimize the number of connections
between the device and the system controller.
Figure 37 shows the data output protocol for ADS1298.
DRDY
CS
SCLK
216 SCLKs
DOUT
STAT
CH1
CH2
CH3
CH4
CH5
CH6
CH7
CH8
24-Bit
24-Bit
24-Bit
24-Bit
24-Bit
24-Bit
24-Bit
24-Bit
24-Bit
DIN
Figure 37. SPI Bus Data Output for the ADS1298 (Eight Channels)
Data Retrieval
Data retrieval can be accomplished in one of two methods. The read data continuous command (see the
RDATAC: Read Data Continuous section) can be used to set the device in a mode to read the data continuously
without sending opcodes. The read data command (see the RDATA: Read Data section) can be used to read
just one data output from the device (see the SPI Command Definitions section for more details). The conversion
data are read by shifting the data out on DOUT. The MSB of the data on DOUT is clocked out on the first SCLK
rising edge. DRDY returns to high on the first SCLK falling edge. DIN should remain low for the entire read
operation.
The number of bits in the data output depends on the number of channels and the number of bits per channel.
For the ADS1298/8R, the number of data outputs is (24 status bits + 24 bits × 8 channels) = 216 bits. The format
of the 24 status bits is: (1100 + LOFF_STATP + LOFF_STATN + bits[4:7] of the GPIO register). The data format
for each channel data are twos complement and MSB first. When channels are powered down using the user
register setting, the corresponding channel output is set to '0'. However, the sequence of channel outputs
remains the same. For the ADS1294/4R and ADS1296/6R, the last four and two channel outputs shown in
Figure 37 are zeros. The four and six channels parts require only 120 and 168 SCLKs to shift data out,
respectively. Status and GPIO register bits are loaded into the 24-bit status word 2tCLKs before DRDY goes low.
The ADS129x also provide a multiple readback feature. The data can be read out multiple times by simply giving
more SCLKs, in which case the MSB data byte repeats after reading the last byte. The DAISY_EN bit in
CONFIG1 register must be set to '1' for multiple readbacks.
Data Ready (DRDY)
DRDY is an output. When it transitions low, new conversion data are ready. The CS signal has no effect on the
data ready signal. Regardless of the status of the CS signal, a rising edge on SCLK pulls DRDY high. Hence,
when using multiple devices in the SPI bus, it is recommended that SCLK be gated with CS. The behavior of
DRDY is determined by whether the device is in RDATAC mode or the RDATA command is being used to read
data on demand. (See the RDATAC: Read Data Continuous and RDATA: Read Data subsections of the SPI
Command Definitions section for further details).
When reading data with the RDATA command, the read operation can overlap the occurrence of the next DRDY
without data corruption.
The START pin or the START command is used to place the device either in normal data capture mode or pulse
data capture mode.
32
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Figure 38 shows the relationship between DRDY, DOUT, and SCLK during data retrieval (in case of an ADS1298
with a selected data rate that gives 24-bit resolution). DOUT is latched out at the rising edge of SCLK. DRDY is
pulled high at the falling edge of SCLK. Note that DRDY goes high on the first falling edge SCLK regardless of
whether data are being retrieved from the device or a command is being sent through the DIN pin.
DRDY
Bit 215
DOUT
Bit 214
Bit 213
SCLK
Figure 38. DRDY with Data Retrieval (CS = 0 in RDATA mode)
GPIO
The ADS129x have a total of four general-purpose digital I/O (GPIO) pins available in the normal mode of
operation. The digital I/O pins are individually configurable as either inputs or as outputs through the GPIOC bits
register. The GPIOD bits in the GPIO register control the level of the pins. When reading the GPIOD bits, the
data returned are the logic level of the pins, whether they are programmed as inputs or outputs. When the GPIO
pin is configured as an input, a write to the corresponding GPIOD bit has no effect. When configured as an
output, a write to the GPIOD bit sets the output value.
If configured as inputs, these pins must be driven (do not float). The GPIO pins are set as inputs after power-on
or after a reset. Figure 39 shows the GPIO port structure. The pins should be shorted to DGND if not used.
GPIO1 can be used as the PACEIN signal; GPIO2 is multiplexed with RESP_BLK signal; GPIO3 is multiplexed
with the RESP signal; and GPIO4 is multiplexed with the RESP_PH signal.
GPIO Data (read)
GPIO Pin
GPIO Data (write)
GPIO Control
Figure 39. GPIO Port Pin
Power-Down (PWDN)
When PWDN is pulled low, all on-chip circuitry is powered down. To exit power-down mode, take the PWDN pin
high. Upon exiting from power-down mode, the internal oscillator and the reference require time to wake up. It is
recommended that during power-down the external clock is shut down to save power.
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Reset (RESET)
There are two methods to reset the ADS129x: pull the RESET pin low, or send the RESET opcode command.
When using the RESET pin, take it low to force a reset. Make sure to follow the minimum pulse width timing
specifications before taking the RESET pin back high. The RESET command takes effect on the eighth SCLK
falling edge of the opcode command. On reset it takes 18 tCLK cycles to complete initialization of the configuration
registers to the default states and start the conversion cycle. Note that an internal RESET is automatically issued
to the digital filter whenever registers CONFIG1 and RESP are set to new values with a WREG command.
START
The START pin must be set high for at least 2 tCLKs or the START command sent to begin conversions. When
START is low or if the START command has not been sent, the device does not issue a DRDY signal
(conversions are halted).
When using the START opcode to control conversion, hold the START pin low. The ADS129x feature two modes
to control conversion: continuous mode and single-shot mode. The mode is selected by SINGLE_SHOT (bit 3 of
the CONFIG4 register). In multiple device configurations the START pin is used to synchronize devices (see the
Multiple Device Configuration subsection of the SPI Interface section for more details).
Settling Time
The settling time (tSETTLE) is the time it takes for the converter to output fully settled data when START signal is
pulled high. Once START is pulled high, DRDY is also pulled high. The next falling edge of DRDY indicates that
data are ready. Figure 40 shows the timing diagram and Table 9 shows the settling time for different data rates.
The settling time depends on fCLK and the decimation ratio (controlled by the DR[2:0] bits in the CONFIG1
register). Table 8 shows the settling time as a function of tCLK. Note that when START is held high and there is a
step change in the input signal, it takes 3 × tDR for the filter to settle to the new value. Settled data are available
on the fourth DRDY pulse. This time must be considered when trying to measure narrow PACE pulses for PACE
detection.
tSETTLE
START Pin
or
DIN
START Opcode
tDR
4/fCLK
DRDY
Figure 40. Settling Time
Table 9. Settling Times for Different Data Rates
34
DR[2:0]
HIGH-RESOLUTION MODE
LOW-POWER MODE
UNIT
000
001
296
584
tCLK
584
1160
tCLK
010
1160
2312
tCLK
011
2312
4616
tCLK
100
4616
9224
tCLK
101
9224
18440
tCLK
110
18440
36872
tCLK
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Continuous Mode
Conversions begin when the START pin is taken high for at least 2 tCLKs or when the START opcode command
is sent. As seen in Figure 41, the DRDY output goes high when conversions are started and goes low when data
are ready. Conversions continue indefinitely until the START pin is taken low or the STOP opcode command is
transmitted. When the START pin is pulled low or the stop command is issued, the conversion in progress is
allowed to complete. Figure 42 and Table 10 show the required timing of DRDY to the START pin and the
START/STOP opcode commands when controlling conversions in this mode. To keep the converter running
continuously, the START pin can be permanently tied high. Note that when switching from pulse mode to
continuous mode, the START signal is pulsed or a STOP command must be issued followed by a START
command. This conversion mode is ideal for applications that require a fixed-continuous stream of conversions
results.
START Pin
or
or
(1)
DIN
(1)
START
Opcode
STOP
Opcode
tDR
tSETTLE
DRDY
(1)
START and STOP opcode commands take effect on the seventh SCLK falling edge.
Figure 41. Continuous Conversion Mode
tSDSU
DRDY and DOUT
tDSHD
START Pin
or
STOP Opcode
(1)
STOP(1)
STOP(1)
START and STOP commands take effect on the seventh SCLK falling edge at the end of the opcode transmission.
Figure 42. START to DRDY Timing
Table 10. Timing Characteristics for Figure 42 (1)
SYMBOL
(1)
MIN
UNIT
tSDSU
START pin low or STOP opcode to DRDY setup time
to halt further conversions
DESCRIPTION
16
tCLK
tDSHD
START pin low or STOP opcode to complete current
conversion
16
tCLK
START and STOP commands take effect on the seventh SCLK falling edge at the end of the opcode transmission.
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Single-Shot Mode
The single-shot mode is enabled by setting the SINGLE_SHOT bit in CONFIG4 register to '1'. In single-shot
mode, the ADS129x perform a single conversion when the START pin is taken high or when the START opcode
command is sent. As seen in Figure 42, when a conversion is complete, DRDY goes low and further conversions
are stopped. Regardless of whether the conversion data are read or not, DRDY remains low. To begin a new
conversion, take the START pin low and then back high for at least 2 tCLKs, or transmit the START opcode again.
Note that when switching from continuous mode to pulse mode, make sure the START signal is pulsed or issue
a STOP command followed by a START command.
START
tSETTLE
4/fCLK
Data Updating
4/fCLK
DRDY
Figure 43. DRDY with No Data Retrieval in Single-Shot Mode
This conversion mode is provided for applications that require non-standard or non-continuous data rates.
Issuing a START command or toggling the START pin high resets the digital filter, effectively dropping the data
rate by a factor of four. This mode leaves the system more susceptible to aliasing effects, thus requiring more
complex analog or digital filtering. Loading on the host processor increases because it must toggle the START
pin or send a START command to initiate a new conversion cycle.
MULTIPLE DEVICE CONFIGURATION
The ADS129x are designed to provide configuration flexibility when multiple devices are used in a system. The
serial interface typically requires four signals: DIN, DOUT, SCLK, and CS. With one additional chip select signal
per device, multiple devices can be connected together. The number of signals needed to interface n devices is
3 + n.
The right leg drive amplifiers can be daisy-chained as explained in the RLD Configuration with Multiple Devices
subsection of the ECG-Specific Functions section. To use the internal oscillator in a daisy-chain configuration,
one of the devices must be set as the master for the clock source with the internal oscillator enabled (CLKSEL
pin = 1) and the internal oscillator clock brought out of the device by setting the CLK_EN register bit to '1'. This
master device clock is used as the external clock source for the other devices.
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When using multiple devices, the devices can be synchronized with the START signal. The delay from START to
the DRDY signal is fixed for a fixed data rate (see the START subsection of the SPI Interface section for more
details on the settling times). Figure 44 shows the behavior of two devices when synchronized with the START
signal as an example.
There are two ways to connect multiple devices with a optimal number of interface pins: cascade mode and
daisy-chain mode.
ADS12981
START
CLK
START1
DRDY
DRDY1
CLK
ADS12982
START2
DRDY
DRDY2
CLK
CLK
START
DRDY1
DRDY2
Figure 44. Synchronizing Multiple Converters
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Cascaded Mode
Figure 45a shows a configuration with two devices cascaded together. One of the devices is an ADS1298 (eight
channels) and the other is an ADS1294 (four channels). Together, they create a system with 12 channels.
DOUT, SCLK, and DIN are shared. Each device has its own chip select. When a device is not selected by the
corresponding CS being driven to logic 1, the DOUT of this device is high-impedance. This structure allows the
other device to take control of the DOUT bus. This configuration method is suitable for the majority of
applications.
Daisy-Chain Mode
Daisy-chain mode is enabled by setting the DAISY_EN bit in the CONFIG1 register. Figure 45b shows the
daisy-chain configuration. In this mode SCLK, DIN, and CS are shared across multiple devices. The DOUT of
one device is hooked up to the DAISY_IN of the other device, thereby creating a chain. One extra SCLK must be
issued between each data set. Also, when using daisy-chain mode, the multiple readback feature is not
available. Short the DAISY_IN pin to digital ground if not used. Figure 2 describes the required timing for the
ADS1298 shown in Figure 46. Data from the ADS1298 appear first on DOUT, followed by a don’t care bit, and
finally by the status and data words from the ADS1294.
START
(1)
CLK
START
CLK
START
INT
DRDY
CS
(1)
START
CLK
GPO0
DRDY
CLK
INT
CS
GPO
GPO1
ADS1298
(Device 1)
SCLK
SCLK
MOSI
ADS1298
(Device 1)
SCLK
DIN
DIN
SCLK
MOSI
DOUT
MISO
DAISY_IN1
DOUT1
MISO
Host Processor
START
Host Processor
DOUT2
DRDY
CLK
CS
SCLK
SCLK
CLK
DIN
ADS1294
(Device 2)
DRDY
CS
START
DIN
ADS1294
(Device 2)
DOUT
DAISY_IN2
0
b) Daisy-Chain Configuration
a) Cascaded Configuration
(1) To reduce pin count, set the START pin low and use the START serial command to synchronize and start conversions.
Figure 45. Multiple Device Configurations
DOUT1
DAISY_IN0
1
SCLK
DOUT
LSB1
MSB1
0
3
2
216
LSB0
MSB0
Data from first device (ADS1298)
219
218
217
XX
MSB1
338
LSB1
Data from second device (ADS1294)
Figure 46. Daisy-Chain Timing for Figure 45b
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In a case where all devices in the chain operate in the same register setting, DIN can be shared as well and
thereby reduce the SPI communication signals to four, regardless of the number of devices. However, because
the individual devices cannot be programmed, the RLD driver cannot be shared among the multiple devices.
Furthermore, an external clock must be used.
Note that from Figure 2, the SCLK rising edge shifts data out of the ADS129x on DOUT. The SCLK rising edge is
also used to latch data into the device DAISY_IN pin down the chain. This architecture allows for a faster SCLK
rate speed, but it also makes the interface sensitive to board level signal delays. The more devices in the chain,
the more challenging it could become to adhere to setup and hold times. A star pattern connection of SCLK to all
devices, minimizing length of DOUT, and other PCB layout techniques help. Placing delay circuits such as
buffers between DOUT and DAISY_IN are ways to mitigate this challenge. One other option is to insert a D
flip-flop between DOUT and DAISY_IN clocked on an inverted SCLK. Note also that daisy-chain mode requires
some software overhead to recombine data bits spread across byte boundaries.
The maximum number of devices that can be daisy-chained depends on the data rate at which the device is
being operated. The maximum number of devices can be estimated with Equation 7.
fSCLK
NDEVICES =
fDR (NBITS)(NCHANNELS) + 24
where:
NBITS = device resolution (depends on data rate), and
NCHANNELS = number of channels in the device (4, 6, or 8).
(7)
For example, when the ADS1298 (eight-channel, 24-bit version) is operated at a 2kSPS data rate with a 4MHz
fSCLK, 10 devices can be daisy-chained.
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SPI COMMAND DEFINITIONS
The ADS129x provide flexible configuration control. The opcode commands, summarized in Table 11, control
and configure the operation of the ADS129x. The opcode commands are stand-alone, except for the register
read and register write operations that require a second command byte plus data. CS can be taken high or held
low between opcode commands but must stay low for the entire command operation (especially for multi-byte
commands). System opcode commands and the RDATA command are decoded by the ADS129x on the seventh
falling edge of SCLK. The register read/write opcodes are decoded on the eighth SCLK falling edge. Be sure to
follow SPI timing requirements when pulling CS high after issuing a command.
Table 11. Opcode Command Definitions
COMMAND
DESCRIPTION
FIRST BYTE
SECOND BYTE
System Commands
WAKEUP
Wake-up from standby mode
0000 0010 (02h)
STANDBY
Enter standby mode
0000 0100 (04h)
RESET
Reset the device
0000 0110 (06h)
START
Start/restart (synchronize) conversions
0000 1000 (08h)
STOP
Stop conversion
0000 1010 (0Ah)
Data Read Commands
RDATAC
Enable Read Data Continuous mode.
This mode is the default mode at power-up. (1)
0001 0000 (10h)
SDATAC
Stop Read Data Continuously mode
0001 0001 (11h)
RDATA
Read data by command; supports multiple read back.
0001 0010 (12h)
Register Read Commands
RREG
Read n nnnn registers starting at address r rrrr
001r rrrr (2xh) (2)
000n nnnn (2)
WREG
Write n nnnn registers starting at address r rrrr
010r rrrr (4xh) (2)
000n nnnn (2)
(1)
(2)
When in RDATAC mode, the RREG command is ignored.
n nnnn = number of registers to be read/written – 1. For example, to read/write three registers, set n nnnn = 0 (0010). r rrrr = starting
register address for read/write opcodes.
WAKEUP: Exit STANDBY Mode
This opcode exits the low-power standby mode; see the STANDBY: Enter STANDBY Mode subsection of the
SPI Command Definitions section. Time is required when exiting standby mode (see the Electrical
Characteristics for details). There are no restrictions on the SCLK rate for this command and it can be
issued any time. Any subsequent command must be sent after 4 tCLK cycles.
STANDBY: Enter STANDBY Mode
This opcode command enters the low-power standby mode. All parts of the circuit are shut down except for the
reference section. The standby mode power consumption is specified in the Electrical Characteristics. There are
no restrictions on the SCLK rate for this command and it can be issued any time. Send a WAKEUP
command to return device to normal operation. Serial interface is active, thus register read/write commands are
permitted while in this mode.
RESET: Reset Registers to Default Values
This command resets the digital filter cycle and returns all register settings to the respective default values. See
the Reset (RESET) subsection of the SPI Interface section for more details. There are no restrictions on the
SCLK rate for this command and it can be issued any time. 18 tCLK cycles are required to execute the
RESET command. Avoid sending any commands during this time.
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START: Start Conversions
This opcode starts data conversions. Tie the START pin low to control conversions by command. If conversions
are in progress this command has no effect. The STOP opcode command is used to stop conversions. If the
START command is immediately followed by a STOP command, there must be a gap of 4 tCLK cycles between
the two commands. When the START opcode is sent to the device, keep the START pin low until the STOP
command is issued. (See the START subsection of the SPI Interface section for more details.) There are no
restrictions on the SCLK rate for this command and it can be issued any time.
STOP: Stop Conversions
This opcode stops conversions. Tie the START pin low to control conversions by command. When the STOP
command is sent, the conversion in progress completes and further conversions are stopped. If conversions are
already stopped, this command has no effect. There are no restrictions on the SCLK rate for this command
and it can be issued any time.
RDATAC: Read Data Continuous
This opcode enables the output of conversion data on each DRDY without the need to issue subsequent read
data opcodes. This mode places the conversion data in the output register and may be shifted out directly. The
read data continuous mode is the default mode of the device and the device defaults to this mode on power-up
and reset.
RDATAC mode is cancelled by the Stop Read Data Continuous command. If the device is in RDATAC mode, a
SDATAC command must be issued before any other commands can be sent to the device. There is no
restriction on the SCLK rate for this command. However, the subsequent data retrieval SCLKs or the SDATAC
opcode command should wait at least 4 tCLK cycles. The timing for RDATAC is shown in Figure 47. As Figure 47
shows, there is a keep out zone of 4 tCLK cycles around the DRDY pulse when this command cannot be issued.
If no data are retrieved from the device, DOUT and DRDY behave similarly in this mode. To retrieve data from
the device after RDATAC command is issued, make sure either the START pin is high or the START command
is issued. Figure 47 shows the recommended way to use the RDATAC command. RDATAC is ideally suited for
applications such as data loggers or recorders where registers are set once and do not need to be re-configured.
START
DRDY
CS
SCLK
tUPDATE
RDATAC Opcode
DIN
Hi-Z
DOUT
Status Register + 8-Channel Data (216 Bits)
(1)
Next Data
tUPDATE = 4/fCLK. Do not read data during this time.
Figure 47. RDATAC Usage
SDATAC: Stop Read Data Continuous
This opcode cancels the Read Data Continuous mode. There is no restriction on the SCLK rate for this
command, but the subsequent command must wait for 4 tCLK cycles.
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RDATA: Read Data
Issue this command after DRDY goes low to read the conversion result (in Stop Read Data Continuous mode).
There is no restriction on the SCLK rate for this command, and there is no wait time needed for the subsequent
commands or data retrieval SCLKs. To retrieve data from the device after RDATA command is issued, make
sure either the START pin is high or the START command is issued. When reading data with the RDATA
command, the read operation can overlap the occurrence of the next DRDY without data corruption. Figure 48
shows the recommended way to use the RDATA command. RDATA is best suited for ECG- and EEG-type
systems where register settings must be read or changed often between conversion cycles.
START
DRDY
CS
SCLK
RDATA Opcode
DIN
RDATA Opcode
Hi-Z
DOUT
Status Register+ 8-Channel Data (216 Bits)
Figure 48. RDATA Usage
Sending Multi-Byte Commands
The ADS129x serial interface decodes commands in bytes and requires 4 tCLK cycles to decode and execute.
Therefore, when sending multi-byte commands, a 4 tCLK period must separate the end of one byte (or opcode)
and the next.
Assume CLK is 2.048MHz, then tSDECODE (4 tCLK) is 1.96µs. When SCLK is 16MHz, one byte can be transferred
in 500ns. This byte transfer time does not meet the tSDECODE specification; therefore, a delay must be inserted so
the end of the second byte arrives 1.46µs later. If SCLK is 4MHz, one byte is transferred in 2µs. Because this
transfer time exceeds the tSDECODE specification, the processor can send subsequent bytes without delay. In this
later scenario, the serial port can be programmed to cease single-byte transfer per cycle to multiple bytes.
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RREG: Read From Register
This opcode reads register data. The Register Read command is a two-byte opcode followed by the output of the
register data. The first byte contains the command opcode and the register address. The second byte of the
opcode specifies the number of registers to read – 1.
First opcode byte: 001r rrrr, where r rrrr is the starting register address.
Second opcode byte: 000n nnnn, where n nnnn is the number of registers to read – 1.
The 17th SCLK rising edge of the operation clocks out the MSB of the first register, as shown in Figure 49. When
the device is in read data continuous mode, it is necessary to issue a SDATAC command before a RREG
command can be issued. An RREG command can be issued any time. However, because this command is a
multi-byte command, there are restrictions on the SCLK rate depending on the way the SCLKs are issued. See
the Serial Clock (SCLK) subsection of the SPI Interface section for more details. Note that CS must be low for
the entire command.
CS
1
9
17
25
SCLK
DIN
OPCODE 1
OPCODE 2
REG DATA
DOUT
REG DATA + 1
Figure 49. RREG Command Example: Read Two Registers Starting from Register 00h (ID Register)
(OPCODE 1 = 0010 0000, OPCODE 2 = 0000 0001)
WREG: Write to Register
This opcode writes register data. The Register Write command is a two-byte opcode followed by the input of the
register data. The first byte contains the command opcode and the register address.
The second byte of the opcode specifies the number of registers to write – 1.
First opcode byte: 010r rrrr, where r rrrr is the starting register address.
Second opcode byte: 000n nnnn, where n nnnn is the number of registers to write – 1.
After the opcode bytes, the register data follows (in MSB-first format), as shown in Figure 50. WREG command
can be issued any time. However, because this command is a multi-byte command, there are restrictions on the
SCLK rate depending on the way the SCLKs are issued. See the Serial Clock (SCLK) subsection of the SPI
Interface section for more details. Note that CS must be low for the entire command.
CS
1
9
17
25
SCLK
DIN
OPCODE 1
OPCODE 2
REG DATA 1
REG DATA 2
DOUT
Figure 50. WREG Command Example: Write Two Registers Starting from 00h (ID Register)
(OPCODE 1 = 0100 0000, OPCODE 2 = 0000 0001)
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REGISTER MAP
Table 12 lists the various ADS129x registers.
Table 12. Register Assignments
ADDRESS
RESET
VALUE
(Hex)
REGISTER
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
xx
DEV_ID7
DEV_ID6
DEV_ID5
1
0
DEV_ID2
DEV_ID1
DEV_ID0
Device Settings (Read-Only Registers)
00h
ID
Global Settings Across Channels
01h
CONFIG1
06
HR
DAISY_EN
CLK_EN
0
0
DR2
DR1
DR0
02h
CONFIG2
40
0
0
WCT_CHOP
INT_TEST
0
TEST_AMP
TEST_FREQ1
TEST_FREQ0
03h
CONFIG3
40
PD_REFBUF
1
VREF_4V
RLD_MEAS
RLDREF_INT
PD_RLD
RLD_LOFF_
SENS
RLD_STAT
04h
LOFF
00
COMP_TH2
COMP_TH1
COMP_TH0
VLEAD_OFF_
EN
ILEAD_OFF1
ILEAD_OFF0
FLEAD_OFF1
FLEAD_OFF0
Channel-Specific Settings
05h
CH1SET
00
PD1
GAIN12
GAIN11
GAIN10
0
MUXn2
MUXn1
MUXn0
06h
CH2SET
00
PD2
GAIN22
GAIN21
GAIN20
0
MUX22
MUX21
MUX20
07h
CH3SET
00
PD3
GAIN32
GAIN31
GAIN30
0
MUX32
MUX31
MUX30
08h
CH4SET
00
PD4
GAIN42
GAIN41
GAIN40
0
MUX42
MUX41
MUX40
09h
CH5SET (1)
00
PD5
GAIN52
GAIN51
GAIN50
0
MUX52
MUX51
MUX50
0Ah
CH6SET (1)
00
PD6
GAIN62
GAIN61
GAIN60
0
MUX62
MUX61
MUX60
0Bh
CH7SET (1)
00
PD7
GAIN72
GAIN71
GAIN70
0
MUX72
MUX71
MUX70
0Ch
CH8SET (1)
00
PD8
GAIN82
GAIN81
GAIN80
0
MUX82
MUX81
MUX80
0Dh
RLD_SENSP
(2)
00
RLD8P (1)
RLD7P (1)
RLD6P (1)
RLD5P (1)
RLD4P
RLD3P
RLD2P
RLD1P
0Eh
RLD_SENSN
(2)
00
RLD8N (1)
RLD7N (1)
RLD6N (1)
RLD5N (1)
RLD4N
RLD3N
RLD2N
RLD1N
0Fh
LOFF_SENSP
(2)
00
LOFF8P
LOFF7P
LOFF6P
LOFF5P
LOFF4P
LOFF3P
LOFF2P
LOFF1P
10h
LOFF_SENSN
(2)
00
LOFF8N
LOFF7N
LOFF6N
LOFF5N
LOFF4N
LOFF3N
LOFF2N
LOFF1N
11h
LOFF_FLIP
00
LOFF_FLIP8
LOFF_FLIP7
LOFF_FLIP6
LOFF_FLIP5
LOFF_FLIP4
LOFF_FLIP3
LOFF_FLIP2
LOFF_FLIP1
Lead-Off Status Registers (Read-Only Registers)
12h
LOFF_STATP
00
IN8P_OFF
IN7P_OFF
IN6P_OFF
IN5P_OFF
IN4P_OFF
IN3P_OFF
IN2P_OFF
IN1P_OFF
13h
LOFF_STATN
00
IN8N_OFF
IN7N_OFF
IN6N_OFF
IN5N_OFF
IN4N_OFF
IN3N_OFF
IN2N_OFF
IN1N_OFF
GPIO and OTHER Registers
(1)
(2)
44
14h
GPIO
0F
GPIOD4
GPIOD3
GPIOD2
GPIOD1
GPIOC4
GPIOC3
GPIOC2
GPIOC1
15h
PACE
00
0
0
0
PACEE1
PACEE0
PACEO1
PACEO0
PD_PACE
16h
RESP
00
RESP_
DEMOD_EN1
RESP_MOD_
EN1
1
RESP_PH2
RESP_PH1
RESP_PH0
RESP_CTRL1
RESP_CTRL0
17h
CONFIG4
00
RESP_FREQ2
RESP_FREQ1
RESP_FREQ0
0
SINGLE_
SHOT
WCT_TO_
RLD
PD_LOFF_
COMP
0
18h
WCT1
00
aVF_CH6
aVL_CH5
aVR_CH7
avR_CH4
PD_WCTA
WCTA2
WCTA1
WCTA0
19h
WCT2
00
PD_WCTC
PD_WCTB
WCTB2
WCTB1
WCTB0
WCTC2
WCTC1
WCTC0
CH5SET and CH6SET are not available for the ADS1294/4R. CH7SET and CH8SET registers are not available for the ADS1294/4R
and ADS1296/6R.
The RLD_SENSP, PACE_SENSP, LOFF_SENSP, LOFF_SENSN, and LOFF_FLIP registers bits[5:4] are not available for the
ADS1294/4R. Bits[7:6] are not available for the ADS1294/6/4R/6R.
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User Register Description
ID: ID Control Register (Factory-Programmed, Read-Only)
Address = 00h
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
DEV_ID7
DEV_ID6
DEV_ID5
1
0
DEV_ID2
DEV_ID1
DEV_ID0
The ID Control Register is programmed during device manufacture to indicate device characteristics.
Bits[7:5]
DEV_ID[7:5]: Device family identification
These bits indicate the device family.
000 = Reserved
011 = Reserved
100 = ADS129x device family
101 = Reserved
110 = ADS129xR device family
111 = Reserved
Bit 4
This bit reads high.
Bit 3
This bit reads low.
Bits[2:0]
DEV_ID[2:0]: Channel number identification
These bits indicates number of channels.
000 = 4-channel ADS1294 or ADS1294R
001 = 6-channel ADS1296 or ADS1296R
010 = 8-channel ADS1298 or ADS1298R
011 = Reserved
111 = Reserved
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CONFIG1: Configuration Register 1
Address = 01h
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
HR
DAISY_EN
CLK_EN
0
0
DR2
DR1
DR0
Bit 7
HR: High-Resolution/Low-Power mode
This bit determines whether the device runs in Low-Power or High-Resolution mode.
0 = Low-Power mode (default)
1 = High-Resolution mode
Bit 6
DAISY_EN: Daisy-chain/multiple readback mode
This bit determines which mode is enabled.
0 = Daisy-chain mode (default)
1 = Multiple readback mode
CLK_EN: CLK connection (1)
Bit 5
This bit determines if the internal oscillator signal is connected to the CLK pin when the CLKSEL pin = 1.
0 = Oscillator clock output disabled (default)
1 = Oscillator clock output enabled
Bits[4:3]
Must always be set to '0'
Bits[2:0]
DR[2:0]: Output data rate
For High-Resolution mode, fMOD = fCLK/4. For low power mode, fMOD = fCLK/8.
These bits determine the output data rate of the device.
(1)
(1)
(2)
46
Additional power is consumed when driving external devices.
BIT
DATA RATE
HIGH-RESOLUTION MODE (1)
LOW-POWER MODE (2)
000
fMOD/16
32kSPS
16kSPS
001
fMOD/32
16kSPS
8kSPS
010
fMOD/64
8kSPS
4kSPS
011
fMOD/128
4kSPS
2kSPS
100
fMOD/256
2kSPS
1kSPS
101
fMOD/512
1kSPS
500SPS
110 (default)
fMOD/1024
500SPS
250SPS
111
Do not use
n/a
n/a
Additional power is consumed when driving external devices.
fCLK = 2.048MHz.
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CONFIG2: Configuration Register 2
Address = 02h
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
0
0
WCT_CHOP
INT_TEST
0
TEST_AMP
TEST_FREQ1
TEST_FREQ0
Configuration Register 2 configures the test signal generation. See the Input Multiplexer section for more details.
Bits[7:6]
Must always be set to '0'
Bit 5
WCT_CHOP: WCT chopping scheme
This bit determines whether the chopping frequency of WCT amplifiers is variable or fixed.
0 = Chopping frequency varies, see Table 13
1 = Chopping frequency constant at fMOD/16
Bit 4
INT_TEST: TEST source
This bit determines the source for the Test signal.
0 = Test signals are driven externally (default)
1 = Test signals are generated internally
Bit 3
Must always be set to '0'
Bit 2
TEST_AMP: Test signal amplitude
These bits determine the calibration signal amplitude.
0 = 1 × –(VREFP – VREFN)/2.4mV (default)
1 = 2 × –(VREFP – VREFN)/2.4mV
Bits[1:0]
TEST_FREQ[1:0]: Test signal frequency
These bits determine the calibration signal frequency.
00 = Pulsed at fCLK/221 (default)
01 = Pulsed at fCLK/220
10 = Not used
11 = At dc
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CONFIG3: Configuration Register 3
Address = 03h
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
PD_REFBUF
1
VREF_4V
RLD_MEAS
RLDREF_INT
PD_RLD
RLD_LOFF_SENS
RLD_STAT
Configuration Register 3 configures multi-reference and RLD operation.
Bit 7
PD_REFBUF: Power-down reference buffer
This bit determines the power-down reference buffer state.
0 = Power-down internal reference buffer (default)
1 = Enable internal reference buffer
Bit 6
Must always be set to '1'
Default is '1' at power-up.
Bit 5
VREF_4V: Reference voltage
This bit determines the reference voltage, VREFP.
0 = VREFP is set to 2.4V (default)
1 = VREFP is set to 4V (use only with a 5V analog supply)
Bit 4
RLD_MEAS: RLD measurement
This bit enables RLD measurement. The RLD signal may be measured with any channel.
0 = Open (default)
1 = RLD_IN signal is routed to the channel that has the MUX_Setting 010 (VREF)
Bit 3
RLDREF_INT: RLDREF signal
This bit determines the RLDREF signal source.
0 = RLDREF signal fed externally (default)
1 = RLDREF signal (AVDD – AVSS)/2 generated internally
Bit 2
PD_RLD: RLD buffer power
This bit determines the RLD buffer power state.
0 = RLD buffer is powered down (default)
1 = RLD buffer is enabled
Bit 1
RLD_LOFF_SENS: RLD sense function
This bit enables the RLD sense function.
0 = RLD sense is disabled (default)
1 = RLD sense is enabled
Bit 0
RLD_STAT: RLD lead-off status
This bit determines the RLD status.
0 = RLD is connected (default)
1 = RLD is not connected
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LOFF: Lead-Off Control Register
Address = 04h
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
COMP_TH2
COMP_TH1
COMP_TH0
VLEAD_OFF_EN
ILEAD_OFF1
ILEAD_OFF0
FLEAD_OFF1
FLEAD_OFF0
The Lead-Off Control Register configures the Lead-Off detection operation.
Bits[7:5]
COMP_TH[2:0]: Lead-off comparator threshold
These bits determine the lead-off comparator threshold level setting. See the Lead-Off Detection subsection of the
ECG-Specific Functions section for a detailed description.
Comparator positive side
000 = 95% (default)
001 = 92.5%
010 = 90%
011 = 87.5%
100 = 85%
101 = 80%
110 = 75%
111 = 70%
Comparator negative side
000 = 5% (default)
001 = 7.5%
010 = 10%
011 = 12.5%
100 = 15%
101 = 20%
110 = 25%
111 = 30%
Bit 4
VLEAD_OFF_EN: Lead-off detection mode
This bit determines the lead-off detection mode.
0 = Current source mode lead-off (default)
1 = Pull-up/pull-down resistor mode lead-off
Bits[3:2]
ILEAD_OFF[1:0]: Lead-off current magnitude
These bits determine the magnitude of current for the current lead-off mode.
00 = 6nA (default)
01 = 12nA
10 = 18nA
11 = 24nA
Bits[1:0]
FLEAD_OFF[1:0]: Lead-off frequency
These bits determine the frequency of lead-off detect for each channel.
00 = When any bits of the LOFF_SENSP or LOFF_SENSN registers are turned on, make sure that FLEAD[1:0] are either
set to 01 or 11 (default)
01 = AC lead-off detection at fDR/4
10 = Do not use
11 = DC lead-off detection turned on
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CHnSET: Individual Channel Settings (n = 1 : 8)
Address = 05h to 0Ch
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
PD
GAIN2
GAIN1
GAIN0
0
MUXn2
MUXn1
MUXn0
The CH[1:8]SET Control Register configures the power mode, PGA gain, and multiplexer settings channels. See
the Input Multiplexer section for details. CH[2:8]SET are similar to CH1SET, corresponding to the respective
channels.
Bit 7
PD: Power-down
This bit determines the channel power mode for the corresponding channel.
0 = Normal operation (default)
1 = Channel power-down.
When powering down a channel, it is recommended that the channel be set to input short by setting the appropriate
MUXn[2:0] = 001 of the CHnSET register.
Bits[6:4]
GAIN[2:0]: PGA gain
These bits determine the PGA gain setting.
000 = 6 (default)
001 = 1
010 = 2
011 = 3
100 = 4
101 = 8
110 = 12
Bit 3
Always write '0'
Bits[2:0]
MUXn[2:0]: Channel input
These bits determine the channel input selection.
000 = Normal electrode input (default)
001 = Input shorted (for offset or noise measurements)
010 = Used in conjunction with RLD_MEAS bit for RLD measurements. See the Right Leg Drive (RLD DC Bias Circuit)
subsection of the ECG-Specific Functions section for more details.
011 = MVDD for supply measurement
100 = Temperature sensor
101 = Test signal
110 = RLD_DRP (positive electrode is the driver)
111 = RLD_DRN (negative electrode is the driver)
RLD_SENSP
Address = 0Dh
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
RLD8P
RLD7P
RLD6P
RLD5P
RLD4P
RLD3P
RLD2P
RLD1P
This register controls the selection of the positive signals from each channel for right leg drive derivation. See the
Right Leg Drive (RLD DC Bias Circuit) subsection of the ECG-Specific Functions section for details.
Note that registers bits[5:4] are not available for the ADS1294/4R. Bits[7:6] are not available for the
ADS1294/6/4R/6R.
RLD_SENSN
Address = 0Eh
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
RLD8N
RLD7N
RLD6N
RLD5N
RLD4N
RLD3N
RLD2N
RLD1N
This register controls the selection of the negative signals from each channel for right leg drive derivation. See
the Right Leg Drive (RLD DC Bias Circuit) subsection of the ECG-Specific Functions section for details.
Note that registers bits[5:4] are not available for the ADS1294/4R. Bits[7:6] are not available for the
ADS1294/6/4R/6R.
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LOFF_SENSP
Address = 0Fh
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
LOFF8P
LOFF7P
LOFF6P
LOFF5P
LOFF4P
LOFF3P
LOFF2P
LOFF1P
This register selects the positive side from each channel for lead-off detection. See the Lead-Off Detection
subsection of the ECG-Specific Functions section for details. Note that the LOFF_STATP register bits are only
valid if the corresponding LOFF_SENSP bits are set to '1'.
Note that registers bits[5:4] are not available for the ADS1294/4R. Bits[7:6] are not available for the
ADS1294/6/4R/6R.
LOFF_SENSN
Address = 10h
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
LOFF8N
LOFF7N
LOFF6N
LOFF5N
LOFF4N
LOFF3N
LOFF2N
LOFF1N
This register selects the negative side from each channel for lead-off detection. See the Lead-Off Detection
subsection of the ECG-Specific Functions section for details. Note that the LOFF_STATN register bits are only
valid if the corresponding LOFF_SENSN bits are set to '1'.
Note that registers bits[5:4] are not available for the ADS1294/4R. Bits[7:6] are not available for the
ADS1294/6/4R/6R.
LOFF_FLIP
Address = 11h
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
LOFF_FLIP8
LOFF_FLIP7
LOFF_FLIP6
LOFF_FLIP5
LOFF_FLIP4
LOFF_FLIP3
LOFF_FLIP2
LOFF_FLIP1
This register controls the direction of the current used for lead-off derivation. See the Lead-Off Detection
subsection of the ECG-Specific Functions section for details.
LOFF_STATP (Read-Only Register)
Address = 12h
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
IN8P_OFF
IN7P_OFF
IN6P_OFF
IN5P_OFF
IN4P_OFF
IN3P_OFF
IN2P_OFF
IN1P_OFF
This register stores the status of whether the positive electrode on each channel is on or off. See the Lead-Off
Detection subsection of the ECG-Specific Functions section for details. Ignore the LOFF_STATP values if the
corresponding LOFF_SENSP bits are not set to '1'.
'0' is lead-on (default) and '1' is lead-off. When the LOFF_SENSEP bits are '0', the LOFF_STATP bits should be
ignored.
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LOFF_STATN (Read-Only Register)
Address = 13h
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
IN8N_OFF
IN7N_OFF
IN6N_OFF
IN5N_OFF
IN4N_OFF
IN3N_OFF
IN2N_OFF
IN1N_OFF
This register stores the status of whether the negative electrode on each channel is on or off. See the Lead-Off
Detection subsection of the ECG-Specific Functions section for details. Ignore the LOFF_STATN values if the
corresponding LOFF_SENSN bits are not set to '1'.
'0' is lead-on (default) and '1' is lead-off. When the LOFF_SENSEN bits are '0', the LOFF_STATP bits should be
ignored.
GPIO: General-Purpose I/O Register
Address = 14h
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
GPIOD4
GPIOD3
GPIOD2
GPIOD1
GPIOC4
GPIOC3
GPIOC2
GPIOC1
The General-Purpose I/O Register controls the action of the three GPIO pins. Note that when RESP_CTRL[1:0]
is in mode 01 and 11, the GPIO2, GPIO3, and GPIO4 pins are not available for use.
Bits[7:4]
GPIOD[4:1]: GPIO data
These bits are used to read and write data to the GPIO ports.
When reading the register, the data returned correspond to the state of the GPIO external pins, whether they are
programmed as inputs or as outputs. As outputs, a write to the GPIOD sets the output value. As inputs, a write to the
GPIOD has no effect. GPIO is not available in certain respiration modes.
Bits[3:0]
GPIOC[4:1]: GPIO control (corresponding GPIOD)
These bits determine if the corresponding GPIOD pin is an input or output.
0 = Output
1 = Input (default)
PACE: PACE Detect Register
Address = 15h
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
0
0
0
PACEE1
PACEE0
PACEO1
PACEO0
PD_PACE
This register provides the PACE controls that configure the channel signal used to feed the external PACE detect
circuitry. See the Pace Detect subsection of the ECG-Specific Functions section for details.
Bits[7:5]
Must always be set to '0'
Bits[4:3]
PACEE[1:0]: PACE even channels
These bits control the selection of the even number channels available on TEST_PACE_OUT1. Note that only one channel
may be selected at any time.
00 = Channel 2 (default)
01 = Channel 4
10 = Channel 6, ADS1296/8/6R/8R only
11 = Channel 8, ADS1298/8R only
Bits[2:1]
PACEO[1:0]: PACE odd channels
These bits control the selection of the odd number channels available on TEST_PACE_OUT2. Note that only one channel
may be selected at any time.
00 = Channel 1 (default)
01 = Channel 3
10 = Channel 5, ADS1296/8/6R/8R only
11 = Channel 7, ADS1298/8R only
Bit 0
PD_PACE: PACE detect buffer
This bit is used to enable/disable the PACE detect buffer.
0 = PACE detect buffer turned off (default)
1 = PACE detect buffer turned on
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RESP: Respiration Control Register
Address = 16h
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
RESP_
DEMOD_EN1
RESP_MOD_
EN1
1
RESP_PH2
RESP_PH1
RESP_PH0
RESP_CTRL1
RESP_CTRL0
This register provides the controls for the respiration circuitry; see the Respiration section for details.
Bit 7
RESP_DEMOD_EN1: Enables respiration demodulation circuitry (ADS1294R/6R/8R only, for ADS1294/6/8 always
write '0')
This bit enables/disables the demodulation circuitry on channel 1.
0 = RESP demodulation circuitry turned off (default)
1 = RESP demodulation circuitry turned on
Bit 6
RESP_MOD_EN1: Enables respiration modulation circuitry (ADS1294R/6R/8R only, for ADS1294/6/8 always write '0')
This bit enables/disables the modulation circuitry on channel 1.
0 = RESP modulation circuitry turned off (default)
1 = RESP modulation circuitry turned on
Bit 5
Reserved
Must always be set to '1' for ADS1294R/6R/8R. This bit does not have any effect for the ADS1294/6/8.
Bits[4:2]
RESP_PH[2:0]: Respiration phase (1)
These bits control the phase of the respiration demodulation control signal. (GPIO4 is out-of-phase with GPIO3 by the
phase determined by the RESP_PH bits.)
000 = 22.5° (default)
001 = 45°
010 = 67.5°
011 = 90°
100 = 112.5°
101 = 135°
110 = 157.5°
111 = N/A
Bits[1:0]
RESP_CTRL[1:0]: Respiration control
These bits set the mode of the respiration circuitry.
00 = No respiration (default)
01= External respiration
10 = Internal respiration with internal signals
11 = Internal respiration with user-generated signals
(1)
RESP_PH[2:0] phase control bits only for internal respiration (RESP_CTRL = 10) and external respiration (RESP_CTRL = 01) modes
when the CONFIG4.RESP_FREQ[2:0] register bits are 000b or 001b.
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CONFIG4: Configuration Register 4
Address = 17h
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
RESP_FREQ2
RESP_FREQ1
RESP_FREQ0
0
SINGLE_SHOT
WCT_TO_RLD
PD_LOFF_COMP
0
Bits[7:5]
RESP_FREQ[2:0]: Respiration modulation frequency
These bits control the respiration control frequency when RESP_CTRL[1:0] = 10 or RESP_CTRL[1:0] = 10 (1).
000 = 64kHz modulation clock
001 = 32kHz modulation clock
010 = 16kHz square wave on GPIO3 and GPIO04. Output on GPIO4 is 180 degree out of phase with GPIO3.
011 = 8kHz square wave on GPIO3 and GPIO04. Output on GPIO4 is 180 degree out of phase with GPIO3.
100 = 4kHz square wave on GPIO3 and GPIO04. Output on GPIO4 is 180 degree out of phase with GPIO3.
101 = 2kHz square wave on GPIO3 and GPIO04. Output on GPIO4 is 180 degree out of phase with GPIO3.
110 = 1kHz square wave on GPIO3 and GPIO04. Output on GPIO4 is 180 degree out of phase with GPIO3.
111 = 500Hz square wave on GPIO3 and GPIO04. Output on GPIO4 is 180 degree out of phase with GPIO3.
Modes 000 and 001 are modulation frequencies in internal and external respiration modes. In internal respiration mode, the
control signals appear at the RESP_MODP and RESP_MODN terminals. All other bit settings generate square waves as
described above on GPIO4 and GPIO3.
(1)
These frequencies assume fCLK = 2.048MHz.
Bit 4
Must always be set to '0'
Bit 3
SINGLE_SHOT: Single-shot conversion
This bit sets the conversion mode.
0 = Continuous conversion mode (default)
1 = Single-shot mode
Bit 2
WCT_TO_RLD: Connects the WCT to the RLD
This bit connects WCT to RLD.
0 = WCT to RLD connection off (default)
1 = WCT to RLD connection on
Bit 1
PD_LOFF_COMP: Lead-off comparator power-down
This bit powers down the lead-off comparators.
0 = Lead-off comparators disabled (default)
1 = Lead-off comparators enabled
Bit 0
54
Must always be set to '0'
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WCT1: Wilson Central Terminal and Augmented Lead Control Register
Address = 18h
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
aVF_CH6
aVL_CH5
aVR_CH7
aVR_CH4
PD_WCTA
WCTA2
WCTA1
WCTA0
The WCT1 control register configures the device WCT circuit channel selection and the augmented leads.
Bit 7
aVF_CH6: Enable (WCTA + WCTB)/2 to the negative input of channel 6 (ADS1296/8/6R/8R)
0 = Disabled (default)
1 = Enabled
Bit 6
aVL_CH5: Enable (WCTA + WCTC)/2 to the negative input of channel 5 (ADS1296/8/6R/8R)
0 = Disabled (default)
1 = Enabled
Bit 5
aVR_CH7: Enable (WCTB + WCTC)/2 to the negative input of channel 7 (ADS1298/8R)
0 = Disabled (default)
1 = Enabled
Bit 4
aVR_CH4: Enable (WCTB + WCTC)/2 to the negative input of channel 4
0 = Disabled (default)
1 = Enabled
Bit 3
PD_WCTA: Power-down WCTA
0 = Powered down (default)
1 = Powered on
Bits[2:0]
WCTA[2:0]: WCT amplifier A channel selection; typically connected to RA electrode.
These bits select one of the eight electrode inputs of channels 1 to 4.
000 = Channel 1
001 = Channel 1
010 = Channel 2
011 = Channel 2
100 = Channel 3
101 = Channel 3
110 = Channel 4
111 = Channel 4
positive input connected to WCTA amplifier (default)
negative input connected to WCTA amplifier
positive input connected to WCTA amplifier
negative input connected to WCTA amplifier
positive input connected to WCTA amplifier
negative input connected to WCTA amplifier
positive input connected to WCTA amplifier
negative input connected to WCTA amplifier
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WCT2: Wilson Central Terminal Control Register
Address = 19h
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
PD_WCTC
PD_WCTB
WCTB2
WCTB1
WCTB0
WCTC2
WCTC1
WCTC0
The WCT2 configuration register configures the device WCT circuit channel selection.
Bit 7
PD_WCTC: Power-down WCTC
0 = Powered down (default)
1 = Powered on
Bit 6
PD_WCTB: Power-down WCTB
0 = Powered down (default)
1 = Powered on
Bits[5:3]
WCTB[2:0]: WCT amplifier B channel selection; typically connected to LA electrode.
These bits select one of the eight electrode inputs of channels 1 to 4.
000 = Channel 1
001 = Channel 1
010 = Channel 2
011 = Channel 2
100 = Channel 3
101 = Channel 3
110 = Channel 4
111 = Channel 4
Bits[2:0]
positive input connected to WCTB amplifier (default)
negative input connected to WCTB amplifier
positive input connected to WCTB amplifier
negative input connected to WCTB amplifier
positive input connected to WCTB amplifier
negative input connected to WCTB amplifier
positive input connected to WCTB amplifier
negative input connected to WCTB amplifier
WCTC[2:0]: WCT amplifier C channel selection; typically connected to LL electrode.
These bits select one of the eight electrode inputs of channels 1 to 4.
000 = Channel 1
001 = Channel 1
010 = Channel 2
011 = Channel 2
100 = Channel 3
101 = Channel 3
110 = Channel 4
111 = Channel 4
56
positive input connected to WCTC amplifier (default)
negative input connected to WCTC amplifier
positive input connected to WCTC amplifier
negative input connected to WCTC amplifier
positive input connected to WCTC amplifier
negative input connected to WCTC amplifier
positive input connected to WCTC amplifier
negative input connected to WCTC amplifier
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ECG-SPECIFIC FUNCTIONS
INPUT MULTIPLEXER (REROUTING THE RIGHT LEG DRIVE SIGNAL)
The input multiplexer has ECG-specific functions for the right leg drive signal. The RLD signal is available at the
RLDOUT pin once the appropriate channels are selected for the RLD derivation, feedback elements are installed
external to the chip, and the loop is closed. This signal can be fed after filtering or fed directly into the RLDIN pin
as shown in Figure 51. This RLDIN signal can be multiplexed into any one of the input electrodes by setting the
MUX bits of the appropriate channel set registers to 110 for P-side or 111 for N-side. Figure 51 shows the RLD
signal generated from channels 1, 2, and 3 and routed to the N-side of channel 8. This feature can be used to
dynamically change the electrode that is used as the reference signal to drive the patient body. Note that the
corresponding channel cannot be used and can be powered down.
RLD_SENSP[0] = 1
IN1P
EMI
Filter
PGA1
RLD_SENSN[0] = 1
MUX1[2:0] = 000
IN1N
RLD_SENSP[1] = 1
IN2P
EMI
Filter
PGA2
RLD_SENSN[1] = 1
MUX2[2:0] = 000
IN2N
RLD_SENSP[2] = 1
IN3P
EMI
Filter
PGA3
RLD_SENSN[2] = 1
MUX3[2:0] = 000
¼
¼
¼
IN3N
RLD_SENSP[7] = 0
IN8P
EMI
Filter
PGA8
MUX8[2:0] = 111
RLD_SENSN[7] = 0
IN8N
MUX
ADS1298
RLDIN
RLDREF_INT
RLDREF_INT
(AVDD + AVSS)/2
RLDREF
Filter or
Feedthrough
RLD_AMP
RLDOUT
1MW
RLDINV
(1)
1.5nF
(1)
(1) Typical values for example only.
Figure 51. Example of RLDOUT Signal Configured to be Routed to IN8N
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INPUT MULTIPLEXER (MEASURING THE RIGHT LEG DRIVE SIGNAL)
Also, the RLDOUT signal can be routed to a channel (that is not used for the calculation of RLD) for
measurement. Figure 52 shows the register settings to route the RLDIN signal to channel 8. The measurement is
done with respect to the voltage on the RLDREF pin. If RLDREF is chosen to be internal, it would be at (AVDD +
AVSS)/2. This feature is useful for debugging purposes during product development.
RLD_SENSP[0] = 1
IN1P
EMI
Filter
PGA1
RLD_SENSN[0] = 1
MUX1[2:0] = 000
IN1N
RLD_SENSP[1] = 1
IN2P
EMI
Filter
PGA2
RLD_SENSN[1] = 1
MUX2[2:0] = 000
IN2N
RLD_SENSP[2] = 1
IN3P
EMI
Filter
PGA3
RLD_SENSN[2] = 1
MUX3[2:0] = 000
¼
¼
¼
IN3N
RLD_SENSP[7] = 0
IN8P
EMI
Filter
PGA8
MUX8[2:0] = 010
RLD_SENSN[7] = 0
IN8N
MUX
RLDREF_INT
(AVDD + AVSS)/2
RLDREF_INT
MUX8[2:0] = 010
AND
RLD_MEAS = 1
RLD_AMP
ADS1298
RLD_IN
RLD_REF
Filter or
Feedthrough
RLD_OUT
1MW
RLD_INV
(1)
1.5nF
(1)
(1) Typical values for example only.
Figure 52. RLDOUT Signal Configured to be Read Back by Channel 8
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WILSON CENTRAL TERMINAL (WCT) AND CHEST LEADS
In the standard 12-lead ECG, WCT voltage is defined as the average of Right Arm (RA), Left Arm (LA), and Left
Leg (LL) electrodes. This voltage is used as the reference voltage for the measurement of the chest leads. The
ADS129x has three integrated low-noise amplifiers that generate the WCT voltage. Figure 53 shows the block
diagram of the implementation.
IN1P
IN1N
IN2P
IN2N
IN3P
IN3N
IN4P
IN4N
To Channel
PGAs
8:1 MUX
8:1 MUX
30kW
Wctb
WCT2[2:0]
WCT2[5:3]
WCT1[2:0]
Wcta
8:1 MUX
Wctc
30kW
30kW
WCT
80pF
AVSS
ADS1294/6/8
Figure 53. WCT Voltage
The devices provide flexibility to choose any one of the eight signals (IN1P to IN4N) to be routed to each of the
amplifiers to generate the average. Having this flexibility allows the RA, LA, and LL electrodes to be connected to
any input of the first four channels depending on the lead configuration.
Each of the three amplifiers in the WCT circuitry can be powered down individually with register settings. By
powering up two amplifiers, the average of any two electrodes can be generated at the WCT pin. Powering up
one amplifier provides the buffered electrode voltage at the WCT pin. Note that the WCT amplifiers have limited
drive strength and thus should be buffered if used to drive a low-impedance load.
See Table 5 for performance when using any 1, 2, or 3 of the WCT buffers.
As can be seen in Table 5, the overall noise reduces when more than one WCT amplifier is powered up. This
noise reduction is a result of the fact that noise is averaged by the passive summing network at the output of the
amplifiers. Powering down individual buffers gives negligible power savings because a significant portion of the
circuitry is shared between the three amplifiers. The bandwidth of the WCT node is limited by the RC network.
The internal summing network consists of three 30kΩ resistors and a 80pF capacitor. It is recommended that an
external 100pF capacitor be added for optimal performance. The effective bandwidth depends on the number of
amplifiers that are powered up, as shown in Table 5.
The WCT node should be only be used to drive very high input impedances (typically greater than 500MΩ).
Typical application would be to connect this WCT signal to the negative inputs of a ADS129x to be used as a
reference signal for the chest leads.
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As mentioned previously in this section, all three WCT amplifiers can be connected to one of eight analog input
pins. The inputs of the amplifiers are chopped and the chopping frequency varies with the data rates of the
ADS129x. The chop frequency for the three highest data rates scale 1:1. For example, at 32kSPS data rate, the
chop frequency is 32kHz in HR mode with WCT_CHOP = 0. The chopping frequency of the four lower data rates
is fixed to 4kHz. When WCT_CHOP = 1, the chop frequency is fixed to highest data rate (that is, fMOD/16)
frequency, as shown in Table 13. The chop frequency shows itself at the output of the WCT amplifiers as a small
square wave riding on dc. The amplitude of the square wave is the offset of the amplifier and is typically 5mVPP.
This artifact as a result of chopping is out-of-band and thus does not interfere with ECG-related measurements.
As a result of the chopping function, the input current leakage on the pins with WCT amplifiers connected sees
increased leakage currents at higher data rates and as the input common voltage swings closer to 0V (AVSS),
as described in Figure 54.
Note that if the output of a channel connected to the WCT amplifier (for example, the V lead channels) is
connected to one of the PACE amplifiers for external PACE detection, the artifact of chopping appears at the
PACE amplifier output.
200
DR = 0.5kSPS, 0.25kSPS
DR = 1kSPS
DR = 2kSPS
DR = 4kSPS
DR = 8kSPS
DR = 16kSPS
DR = 32kSPS
180
160
140
120
100
WCT Input Leakage Current (pA)
WCT Input Leakage Current (pA)
200
80
60
40
20
TA = +25°C
0
0.3
0.8
1.3
1.8
2.3
LP Mode
HR Mode
180
160
140
120
100
80
60
40
20
TA = +25°C
0
0.3
2.8
Input Common-Mode Voltage (V)
0.8
1.3
1.8
2.3
2.8
Input Common-Mode Voltage (V)
Figure 54. WCT Input Leakage Current versus
Input Voltage (WCT_CHOP = 0)
Figure 55. WCT Input Leakage Current versus
Input Voltage (WCT_CHOP = 1)
Table 13. WCT Amplifiers Chop Frequency
60
CONFIG1.DR[2:0] BIT
CONFIG2.WCT_CHOP = 0
CONFIG2.WCT_CHOP = 1
000
fMOD/16
fMOD/16
001
fMOD/32
fMOD/16
010
fMOD/64
fMOD/16
011
fMOD/128
fMOD/16
100
fMOD/128
fMOD/16
101
fMOD/128
fMOD/16
110
fMOD/128
fMOD/16
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Augmented Leads
In the typical implementation of the 12-lead ECG with eight channels, the augmented leads are calculated
digitally. In certain applications, it may be required that all leads be derived in analog rather than digital. The
ADS1298/8R provides the option to generate the augmented leads by routing appropriate averages to channels
5 to 7. The same three amplifiers that are used to generate the WCT signal are used to generate the Goldberger
Central Terminal signals as well. Figure 56 shows an example of generating the augmented leads in analog
domain. Note that in this implementation it takes more than eight channels to generate the standard 12 leads.
Also, this feature is not available in the ADS1296/6R and ADS1294/4R.
IN1P
IN1N
IN2P
IN2N
IN3P
IN3N
IN4P
IN4N
To Channel
PGAs
8:1 MUX
Wctb
8:1 MUX
WCT2[2:0]
WCT2[5:3]
WCT1[2:0]
Wcta
8:1 MUX
Wctc
avF_ch4
ADS1298
avF_ch6
avF_ch5
avF_ch7
IN5P
IN5N
IN6P
IN6N
IN7P
IN7N
To Channel
PGAs
Figure 56. Analog Domain Augmented Leads
Right Leg Drive with the WCT Point
In certain applications, the out-of-phase version of the WCT is used as the right leg drive reference. The
ADS1298 provides the option to have a buffered version of the WCT terminal at the RLD_OUT pin. This signal
can be inverted in phase using an external amplifier and used as the right leg drive. Refer to the Right Leg Drive
(RLD DC Bias Circuit) section for more details.
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LEAD-OFF DETECTION
Patient electrode impedances are known to decay over time. It is necessary to continuously monitor these
electrode connections to verify a suitable connection is present. The ADS129x lead-off detection functional block
provides significant flexibility to the user to choose from various lead-off detection strategies. Though called
lead-off detection, this is in fact an electrode-off detection.
The basic principle is to inject an excitation signal and measure the response to determine if the electrode is off.
As shown in the lead-off detection functional block diagram in Figure 59, this circuit provides two different
methods of determining the state of the patient electrode. The methods differ in the frequency content of the
excitation signal. Lead-off can be selectively done on a per channel basis using the LOFF_SENSP and
LOFF_SENSN registers. Also, the internal excitation circuitry can be disabled and just the sensing circuitry can
be enabled.
DC Lead-Off
In this approach, the lead-off excitation is with a dc signal. The dc excitation signal can be chosen from either a
pull-up/pull-down resistor or a current source/sink, shown in Figure 57. The selection is done by setting the
VLEAD_OFF_EN bit in the LOFF register. One side of the channel is pulled to supply and the other side is pulled
to ground. The pull-up resistor and pull-down resistor can be swapped (as shown in Figure 58) by setting the bits
in the LOFF_FLIP register. In case of current source/sink, the magnitude of the current can be set by using the
ILEAD_OFF[1:0] bits in the LOFF register. The current source/sink gives larger input impedance compared to the
10MΩ pull-up/pull-down resistor.
AVDD
AVDD
AVDD
ADS129x
AVDD
ADS129x
ADS129x
ADS129x
10MW
10MW
INP
INP
INP
PGA
INN
10MW
INP
PGA
PGA
INN
INN
PGA
INN
10MW
10MW
a) Pull-Up/Pull-Down Resistors
b) Current Source
Figure 57. DC Lead-Off Excitation Options
a) LOFF_FLIP = 0
10MW
a) LOFF_FLIP = 1
Figure 58. LOFF_FLIP Usage
Sensing of the response can be done either by looking at the digital output code from the device or by monitoring
the input voltages with an on-chip comparator. If either of the electrodes is off, the pull-up resistors and/or the
pull-down resistors saturate the channel. By looking at the output code it can be determined that either the P-side
or the N-side is off. To pinpoint which one is off, the comparators must be used. The input voltage is also
monitored using a comparator and a 4-bit DAC whose levels are set by the COMP_TH[2:0] bits in the LOFF
register. The output of the comparators are stored in the LOFF_STATP and LOFF_STATN registers. These two
registers are available as a part of the output data stream. (See the Data Output Protocol (DOUT) subsection of
the SPI Interface section.) If dc lead-off is not used, the lead-off comparators can be powered down by setting
the PD_LOFF_COMP bit in the CONFIG4 register.
An example procedure to turn on dc lead-off is given in the Lead-Off subsection of the Guide to Get Up and
Running section.
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AC Lead-Off
This method uses an out-of-band ac signal for excitation. The ac signal is generated by alternatively providing
pull-up resistors and pull-down resistors at the input with a fixed frequency. The ac signal is passed through an
anti-aliasing filter to avoid aliasing. The frequency can be chosen by the FLEAD_OFF[1:0] bits in the LOFF
register. The excitation frequency is a function of the output data rate and is fDR/4. This out-of-band excitation
signal is passed through the channel and measured at the output.
Sensing of the ac signal is done by passing the signal through the channel to digitize it and measure at the
output. The ac excitation signals are introduced at a frequency that is above the band of interest, generating an
out-of-band differential signal that can be filtered out separately and processed. By measuring the magnitude of
the excitation signal at the output spectrum, the lead-off status can be calculated. Therefore, the ac lead-off
detection can be accomplished simultaneously with the ECG signal acquisition.
AVDD
AVSS
FLEAD_OFF[0:1]
Vx
FLEAD_OFF[1:0]
10pF
10pF
7MW
7MW
(AVDD + AVSS)/2
3.3MW
Patient
Skin,
Electrode Contact
Model
Patient
Protection
Resistor
12pF
3.3MW
12pF
3.3MW
3.3MW
3.3MW
Anti-Aliasing Filter
< 512kHz
3.3MW
47nF
51kW
LOFF_STATP
100kW
LOFF_SENSP AND
VLEAD_OFF_EN
LOFF_SENSN AND
VLEAD_OFF_EN
VINP
51kW
100kW
EMI
Filter
LOFF_SENSP AND
VLEAD_OFF_EN
47nF
47nF
51kW
VINN
AVDD
PGA
LOFF_SENSN AND
VLEAD_OFF_EN
AVSS
To ADC
LOFF_STATN
4-Bit
DAC
COMP_TH[2:0]
100kW
RLD OUT
Figure 59. Lead-Off Detection
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RLD LEAD-OFF
The ADS129x provide two modes for determining whether the RLD is correctly connected:
• RLD lead-off detection during normal operation
• RLD lead-off detection during power-up
The following sections provide details of the two modes of operation.
RLD Lead-Off Detection During Normal Operation
During normal operation, the ADS129x RLD lead-off at power-up function cannot be used because it is
necessary to power off the RLD amplifier.
RLD Lead-Off Detection At Power-Up
This feature is included in the ADS129x for use in determining whether the right leg electrode is suitably
connected. At power-up, the ADS129x provide two measurement procedures to determine the RLD electrode
connection status using either a current or a voltage pull-down resistor, as shown in Figure 60. The reference
level of the comparator is set to determine the acceptable RLD impedance threshold.
Patient
Skin,
Electrode Contact
Model
Patient
Protection
Resistor
To ADC input (through VREF
connection to any of the channels).
47nF
51kW
RLD_STAT
100kW
RLD_SENS AND
RLD_SENS AND
VLEAD_OFF_EN
VLEAD_OFF_EN
ILGND_OFF[1:0]
AVSS
AVSS
Figure 60. RLD Lead-Off Detection at Power-Up
When the RLD amplifier is powered on, the current source has no function. Only the comparator can be used to
sense the voltage at the output of the RLD amplifier. The comparator thresholds are set by the same LOFF[7:5]
bits used to set the thresholds for other negative inputs.
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RIGHT LEG DRIVE (RLD DC BIAS CIRCUIT)
The right leg drive (RLD) circuitry is used as a means to counter the common-mode interference in a ECG
system as a result of power lines and other sources, including fluorescent lights. The RLD circuit senses the
common-mode of a selected set of electrodes and creates a negative feedback loop by driving the body with an
inverted common-mode signal. The negative feedback loop restricts the common-mode movement to a narrow
range, depending on the loop gain. Stabilizing the entire loop is specific to the individual user system based on
the various poles in the loop. The ADS129x integrates the muxes to select the channel and an operational
amplifier. All the amplifier terminals are available at the pins, allowing the user to choose the components for the
feedback loop. The circuit shown in Figure 61 shows the overall functional connectivity for the RLD bias circuit.
The reference voltage for the right leg drive can be chosen to be internally generated (AVDD + AVSS)/2 or it can
be provided externally with a resistive divider. The selection of an internal versus external reference voltage for
the RLD loop is defined by writing the appropriate value to the RLDREF_INT bit in the CONFIG3 register.
If the RLD function is not used, the amplifier can be powered down using the PD_RLD bit (see the CONFIG3:
Configuration Register 3 subsection of the Register Map section for details). This bit is also used in daisy-chain
mode to power-down all but one of the RLD amplifiers.
The functionality of the RLDIN pin is explained in the Input Multiplexer section. An example procedure to use the
RLD amplifier is shown in the Right Leg Drive subsection of the Guide to Get Up and Running section.
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From
MUX1P
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RLD1P
220kW
PGA1P
50kW
220kW
RLD2P
PGA2P
20kW
50kW
From
MUX2P
50kW
20kW
220kW
PGA1N
From
MUX1N
RLD1N
From
MUX3P
RLD3P
50kW
220kW
PGA2N
From
MUX2N
RLD2N
220kW
PGA3P
50kW
220kW
RLD4P
PGA4P
20kW
50kW
From
MUX4P
50kW
20kW
220kW
PGA3N
From
MUX3N
RLD3N
From
MUX5P
RLD5P
50kW
220kW
PGA4N
RLD4N
From
MUX4N
RLD6P
From
MUX6P
220kW
PGA5P
50kW
220kW
PGA6P
20kW
50kW
50kW
20kW
220kW
PGA5N
From
MUX5N
RLD5N
From
MUX7P
RLD7P
50kW
220kW
PGA6N
From
MUX6N
RLD6N
220kW
PGA7P
50kW
220kW
RLD8P
PGA8P
20kW
50kW
From
MUX8P
50kW
20kW
220kW
PGA7N
From
MUX7N
RLD7N
PGA8N
RLDINV
(1)
CEXT
1.5nF
RLD8N
(1)
REXT
1MW
RLDOUT
50kW
220kW
RLD
Amp
From
MUX8N
(AVDD + AVSS)/2
RLDREF_INT
RLDREF
RLDREF_INT
(1) Typical values.
(2) When CONFIG3.RLDREF_INT = 0, the RLDREF_INT switch is closed and the RLDREF_INT switch is open. When
CONFIG3.RLDREF_INT = 1, the RLDREF_INT switch is open and the RLDREF_INT switch is closed.
Figure 61. RLD Channel Selection(2)
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WCT as RLD
In certain applications, the right leg drive is derived as the average of RA, LA, and LL. This level is the same as
the WCT voltage. The WCT amplifier has limited drive strength and thus should be used only to drive very high
impedances directly. The ADS129x provide an option to internally buffer the WCT signal by setting the
WCT_TO_RLD bit in the CONFIG4 register. The RLD_OUT and RLD_INV pins should be shorted external to the
device. Note that before the RLD_OUT signal is connected to the RLD electrode, an external amplifier should be
used to invert the phase of the signal for negative feedback.
ADS129x
RLD_INV
RLD_OUT
RLD
Amp
RLD
(AVDD + AVSS)/2
RLDREF_INT
RLD_REF
From WCT Amplifiers
WCT_TO_RLD
RLD_REF
RLDREF_INT
WCT
Figure 62. Using the WCT as the Right Leg Drive
RLD Configuration with Multiple Devices
Figure 63 shows multiple devices connected to an RLD.
RLDIN RLD
REF
VA1-8 VA1-8
RLD
OUT
RLDINV
Device 1
Power-Down
RLDIN RLD
REF
VA1-8 VA1-8
RLD
OUT
RLDINV
To Input MUX
Device 2
To Input MUX
To Input MUX
Device N
Power-Down
VA1-8 VA1-8
RLDIN RLD
REF
RLD
OUT
RLDINV
Figure 63. RLD Connection for Multiple Devices
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PACE DETECT
The ADS129x provide flexibility for PACE detection either in software or by external hardware. The software
approach is made possible by providing sampling rates up to 32kSPS. The external hardware approach is made
possible by bringing out the output of the PGA at two pins: TESTP_PACE_OUT1 and TESTN_PACE_OUT2.
Note that if the WCT amplifier is connected to the signal path, the user sees switching noise as a result of
chopping; see the Wilson Central Terminal (WCT) section for details.
Software Approach
To use the software approach, the device must be operated at 8kSPS or more to be able to capture the fastest
pulse. Afterwards, digital signal processing can be used to identify the presence of the pacemaker pulse. The
software approach gives the utmost flexibility to the user to be able to program the PACE detect threshold on the
fly using software. This becomes increasingly important as pacemakers evolve over time. Two parameters must
be considered while measuring fast PACE pulses:
1. The PGA bandwidth shown in Table 6.
2. For a step change in input, the digital decimation filter takes 3 × tDR to settle. The PGA bandwidth determines
the gain setting that can be used and the settling time determines the data rate that the device must be
operated at.
External Hardware Approach
One of the drawbacks of using the software approach is that all channels on a single device must operate at
higher data rates. For systems where it is of concern, the ADS129x provide the option of bringing out the output
of the PGA. External hardware circuitry can be used to detect the presence of the pulse. The output of the PACE
detection logic can then be fed into the device through one of the GPIO pins. The GPIO data are transmitted
through the SPI port and loaded 2tCLKs before DRDY goes low. Two of the eight channels can be selected using
register bits in the PACE register, one from the odd-numbered channels and the other from the even-numbered
channels. During the differential to single-ended conversion, there is an attenuation of 0.4. Therefore, the total
gain in the PACE path is equal to (0.4 × PGA_GAIN). The PACE out signals are multiplexed with the TESTP and
TESTN signals through the TESTP_PACE_OUT1 and TESTN_PACE_OUT2 pins respectively. The channel
selection is done by setting bits[4:1] of the PACE register. If the PACE circuitry is not used, the PACE amplifiers
can be turned off using the PD_PACE bit in the PACE register.
Note that if the output of a channel connected to the WCT amplifier (for example, the V lead channels) is
connected to one of the PACE amplifiers for external PACE detection, the artifact of chopping appears at the
PACE amplifier output. Refer to the Wilson Central Terminal (WCT) section for more details.
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PACE[2:1]
PACE[4:3]
From
MUX1P
00
PGA1P
50kW
00
PGA2P
20kW
From
MUX2P
50kW
50kW
20kW
PGA1N
From
MUX1N
00
From
MUX3P
01
50kW
PGA2N
00
From
MUX2N
01
From
MUX4P
PGA3P
50kW
PGA4P
20kW
50kW
50kW
20kW
PGA3N
From
MUX3N
01
From
MUX5P
10
50kW
PGA4N
From
MUX4N
01
PGA5P
50kW
10
PGA6P
20kW
From
MUX6P
50kW
50kW
20kW
PGA5N
From
MUX5N
10
From
MUX7P
11
50kW
PGA6N
From
MUX6N
10
PGA7P
50kW
11
PGA8P
20kW
From
MUX8P
50kW
50kW
20kW
PGA7N
From
MUX7N
11
50kW
(AVDD - AVSS)
PGA8N
2
From
MUX8N
11
200kW
PDB_PACE
TESTN_PACE_OUT2
PACE
Amp
500kW
GPIO1
(1)
PACE_IN (GPIO1)
200kW
(AVDD - AVSS)
2
200kW
PDB_PACE
TESTP_PACE_OUT1
PACE
Amp
500kW
200kW
(1) GPIO1 can be used as the PACE_IN signal.
Figure 64. Hardware PACE Detection Option
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RESPIRATION
The ADS1294R/6R/8R provide three modes for respiration impedance measurement: external respiration,
internal respiration using on-chip modulation signals, and internal respiration using user-generated modulation
signals, as shown in Table 14.
Table 14. Respiration Control
RESP.RESP_CTRL[1]
RESP.RESP_CTRL[0]
MODE AVAILABLE
DESCRIPTION
0
0
ADS1294, ADS1296, ADS1298,
ADS1294R, ADS1296R, ADS1298R
0
1
ADS1294, ADS1296, ADS1298,
ADS1294R, ADS1296R, ADS1298R
Generates modulation and demodulation signals for external
respiration circuitry. RESP CLK signals on GPIO2, GPIO3, and
GPIO4.
1
0
ADS1294R, ADS1296R, ADS1298R
Respiration measurement using internally-generated
RESP_MOD signals.
1
1
ADS1294R, ADS1296R,
ADS1298R (1)
Respiration disabled
Respiration measurement using user-generated modulation and
blocking signal.
For more information on respiration impedance measurement, refer to application note Respiration Rate
Measurement Using Impedance Pneumography (SBAA181).
(1)
70
RESP_CTRL[1:0] = 11 is not recommend if CLKSEL = 1 (internal master clock).
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External Respiration Circuitry Option (RESP_CTRL = 01b)
In this mode, GPIO2, GPIO3, and GPIO4 are automatically configured as outputs. The phase relationship
between the signals is shown in Figure 65. GPIO2 is the exclusive-OR of GPIO3 and GPIO4, as shown in
Figure 66. GPIO3 is the modulation signal, and GPIO4 is the de-modulation signal. While in this mode, the
general-purpose pin function of GPIO2, GPIO3, and GPIO4 is not available. The modulation frequency can be
64kHz or 32kHz using RESP_FREQ[2:0] bits in the CONFIG4 register. The remaining bit options of
RESP_FREQ[2:0] generate square waves on GPIO3 and GPIO4. The exclusive-OR out on GPIO2 is only
available on 64kHz and 32kHz modes. The phase of GPIO4, relative to GPIO3, is set by RESP_PH[2:0] bits in
the RESP register.
The mode can be used when the user implements custom respiration impedance circuitry external to the
ADS129x.
(Modulation Clock)
GPIO3
tPHASE
(Demodulation Clock)
GPIO4
tBLKDLY
(Blocking Signal)
GPIO2
Figure 65. External Respiration (RESP_CTRL = 01b) Timing Diagram
Table 15. Timing Characteristics for Figure 65 (1)
2.7V ≤ DVDD ≤ 3.6V
PARAMET
ER
DESCRIPTION
MIN
tPHASE
Respiration phase delay, set by
RESP.RESP_PH[2:0] bits
22.5
tBLKDLY
Modulation clock rising edge to XOR
signal
(1)
TYP
1.65V ≤ DVDD ≤ 2V
MAX
MIN
157.5
22.5
1
TYP
MAX
UNIT
157.5
Degrees
5
ns
Specifications apply from –40°C to +85°C.
CLK
(2.048MHz)
Modulation Clock
GPIO4
Respiration
Modulation
Generator
Demodulation Clock
GPIO3
GPIO2
RESP_PH[2:0]
Figure 66. External Respiration (RESP_CTRL = 01b) Block Diagram
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Internal Respiration Circuitry with Internal Clock (RESP_CTRL = 10b, ADS1294R/6R/8R Only)
Figure 67 shows a block diagram of the internal respiration circuitry. The internal modulation and demodulator
circuitry can be selectively used. The modulation block is controlled by the RESP_MOD_EN bit and the
demodulation block is controlled by the RESP_DEMOD_EN bit. The modulation signal is a square wave of
magnitude VREFP – AVSS. In this mode, the output of the modulation circuitry is available at the RESP_MODP
and RESP_MODN terminals of the device. This availability allows custom filtering to be added to the square
wave modulation signal. In this mode, GPIO2, GPIO3, and GPIO4 can be used for other purposes. The
modulation frequency can be 64kHz or 32kHz, as set by the RESP_FREQ[2:0] bits in the CONFIG4 register. The
phase of the internal demodulation signal is set by the RESP_PH[2:0] bits in the RESP register.
The ADS1294R/6R/8R channel 1 with respiration enabled mode cannot be used to acquire ECG signals. If the
RA and LA leads are intended to measure respiration and ECG signals, the two leads can be wired into channel
1 for respiration and channel 2 for ECG signals.
CLK
Demodulation
Clock
Modulation
Block
RESP_CTRL[1:0]
RESP_CTRL[1:0]
Blocking
Mod. Clock
RESP_MODN
Modulation
Clock
Respiration Clock
Generator
RESP_MODP
I/O
GPIO3
I/O
GPIO4
I/O
GPIO2
IN1P
EMI
Filter
MUX
Ch1
PGA
Demodulation
Block
Ch1
ADC
IN1N
Figure 67. Internal Respiration Block Diagram
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Internal Respiration Circuitry with User-Generated Signals (RESP_CTRL = 11b, ADS1294R/6R/8R Only)
In this mode GPIO2, GPIO3, and GPIO4 are automatically configured as inputs. GPIO2, GPIO3, and GPIO4
cannot be used for other purposes. The signals must be provided as described in Figure 68. The internal master
clock is not recommended in this mode.
(Modulation Clock)
GPIO4
tPHASE
tBLKDLY
(Blocking Signal)
GPIO2
Figure 68. Internal Respiration (RESP_CTRL = 11b) Timing Diagram
Table 16. Timing Characteristics for Figure 68 (1)
1.65V ≤ DVDD ≤ 3.6V
PARAMETER
DESCRIPTION
MIN
tPHASE
Respiration phase delay
0
tBLKDLY
Modulation clock rising edge to XOR signal
(1)
TYP
0
MAX
UNIT
157.5
Degrees
5
ns
Specifications apply from –40°C to +85°C.
ADS129xR Application
The ADS1294R, ADS1296R, and ADS1298R channel 1 with respiration enabled mode cannot be used to
acquire ECG signals. If the RA and LA leads are intended to measure respiration and ECG signals, the two leads
can be wired into channel 1 for respiration and channel 2 for ECG signals, as shown in Figure 69.
R6
10MW
AVDD
R5
10MW
AVSS
C2
0.1mF
IN1P
C1
2.2nF
C3
2.2nF
ADS1294R/6R/8R
R2
40.2kW
RESP_MODP
Left Arm Lead
IN2P
IN2N
RESP_MODN
Right Arm Lead
C6
0.1mF
R4
10MW
C4
2.2nF
R1
40.2kW
C5
2.2nF
AVDD
R3
10MW
IN1N
AVSS
NOTE: Patient and input protection circuitry not shown.
Figure 69. Typical Respiration Circuitry
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Figure 70 shows a respiration test circuit. Figure 71 and Figure 72 plot noise on channel 1 for the
ADS1294R/6R/8R as baseline impedance, gain, and phase are swept. The x-axis is the baseline impedance,
normalized to a 29µA modulation current (as shown in Equation 8).
10
ADS1294R/6R/8R
9.5
Channel 1 Noise (mVPP)
IN1P
R2
40.2kW
RESP_MODP
RBASELINE = 2.21kW
RESP_MODN
R2
40.2kW
9
Phase = 112.5, PGA = 4
Phase = 112.5, PGA = 3
Phase = 135, PGA = 4
Phase = 135, PGA = 3
8.5
8
7.5
7
6.5
6
2214
IN1N
3690
4845
8076
9155
15258
Normalized Baseline Respiration Impedance (W)
Figure 70. Respiration Noise Test Circuit
Figure 71. Channel 1 Noise versus Impedance for
32kHz Modulation Clock and Phase
(BW = 150Hz, Respiration Modulation Clock =
32kHz)
20
Channel 1 Noise (mVPP)
18
16
Phase = 135, PGA = 3
Phase = 135, PGA = 2
Phase = 157, PGA = 3
Phase = 157, PGA = 2
14
12
10
8
6
2214
3690
4845
8076
9155
15258
Normalized Baseline Respiration Impedance (W)
Figure 72. Channel 1 Noise versus Impedance for 64kHz Modulation Clock and Phase
(BW = 150Hz, Respiration Modulation Clock = 64kHz)
RACTUAL ´ IACTUAL
RNORMALIZED =
29mA
where:
RACTUAL is the baseline body impedance,
IACTUAL is the modulation current, as calculated by (VREFP – AVSS) divided by the impedance of the
modulation circuit.
(8)
For example, if modulation frequency = 32kHz, RACTUAL = 3kΩ, IACTUAL = 50µA, and RNORMALIZED = (3kΩ ×
50µA)/29µA = 5.1kΩ.
Referring to Figure 71 and Figure 72, it can be noted that gain = 4 and phase = 112.5° yield the best
performance at 6.4µVPP. Low-pass filtering this signal with a high-order 2Hz cutoff can reduce the noise to less
than 600nVPP. The impedance resolution is 600nVPP/29µA = 20mΩ.
When the modulation frequency is 32kHz, gains of 3 and 4 and phase of 112.5° and 135° are recommended.
When the modulation frequency is 64kHz, gains of 2 and 3 and phase of 135° and 157° are recommended for
best performance.
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QUICK-START GUIDE
PCB LAYOUT
Power Supplies and Grounding
The ADS129x have three supplies: AVDD, AVDD1, and DVDD. Both AVDD and AVDD1 should be as quiet as
possible. AVDD1 provides the supply to the charge pump block and has transients at fCLK. Therefore, it is
recommended that AVDD1 and AVSS1 be star-connected to AVDD and AVSS. It is important to eliminate noise
from AVDD and AVDD1 that is non-synchronous with the ADS129x operation. Each supply of the ADS129x
should be bypassed with 1μF and 0.1μF solid ceramic capacitors. It is recommended that placement of the digital
circuits (DSP, microcontrollers, FPGAs, etc.) in the system is done such that the return currents on those devices
do not cross the analog return path of the ADS129x. The ADS129x can be powered from unipolar or bipolar
supplies.
Capacitors used for decoupling can be of surface-mount, low-cost, low-profile, multi-layer ceramic type. In most
cases, the VCAP1 capacitor can also be a multi-layer ceramic, but in systems where the board is subjected to
high- or low-frequency vibration, it is recommend to install a non-ferroelectric capacitor such as a tantalum or
class 1 capacitor (C0G or NPO). EIA class 2 and class 3 dielectrics such as (X7R, X5R, X8R, etc.) are
ferroelectric. The piezoelectric property of these capacitors can appear as electrical noise coming from the
capacitor. When using internal reference, noise on the VCAP1 node results in performance degradation.
Connecting the Device to Unipolar (+3V/+1.8V) Supplies
Figure 73 illustrates the ADS129x connected to a unipolar supply. In this example, analog supply (AVDD) is
referenced to analog ground (AVSS) and digital supplies (DVDD) are referenced to digital ground (DGND).
+3V
+1.8V
0.1mF
1 mF
1mF
0.1mF
AVDD AVDD1
DVDD
VREFP
VREFN
0.1mF
10mF
VCAP1
RESV1
ADS1298
VCAP2
VCAP3
VCAP4
WCT
AVSS1 AVSS
DGND
1nF
1mF
1mF
0.1mF
1mF
22mF
NOTE: Place the capacitors for supply, reference, WCT, and VCAP1 to VCAP4 as close to the package as possible.
Figure 73. Single-Supply Operation
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Connecting the Device to Bipolar (±1.5V/1.8V) Supplies
Figure 74 illustrates the ADS129x connected to a bipolar supply. In this example, the analog supplies connect to
the device analog supply (AVDD). This supply is referenced to the device analog return (AVSS), and the digital
supply (DVDD) is referenced to the device digital ground return (DGND).
+1.5V
+1.8V
1mF
0.1mF
0.1mF
1 mF
AVDD AVDD1 DVDD
VREFP
10mF
0.1mF
VREFN
-1.5V
VCAP1
RESV1
ADS1298
VCAP2
VCAP3
VCAP4
WCT
AVSS1 AVSS
DGND
1nF
1mF
1mF
1 mF
0.1mF
1mF
22mF
0.1mF
-1.5V
NOTE: Place the capacitors for supply, reference, WCT, and VCAP1 to VCAP4 as close to the package as possible.
Figure 74. Bipolar Supply Operation
Shielding Analog Signal Paths
As with any precision circuit, careful PCB layout ensures the best performance. It is essential to make short,
direct interconnections and avoid stray wiring capacitance—particularly at the analog input pins and AVSS.
These analog input pins are high-impedance and extremely sensitive to extraneous noise. The AVSS pin should
be treated as a sensitive analog signal and connected directly to the supply ground with proper shielding.
Leakage currents between the PCB traces can exceed the input bias current of the ADS129x if shielding is not
implemented. Digital signals should be kept as far as possible from the analog input signals on the PCB.
Analog Input Structure
The analog input of the ADS129x is as shown in Figure 75.
AVDD
INxP,
INxN
5kW
10pF
AVSS
Figure 75. Analog Input Protection Circuit
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POWER-UP SEQUENCING
Before device power-up, all digital and analog inputs must be low. At the time of power-up, all of these signals
should remain low until the power supplies have stabilized, as shown in Figure 76. At this time, begin supplying
the master clock signal to the CLK pin. Wait for time tPOR, then transmit a RESET pulse. After releasing RESET,
the configuration register must be programmed, see the CONFIG1: Configuration Register 1 subsection of the
Register Map section for details. The power-up sequence timing is shown in Table 17.
tPOR
Power Supplies
tRST
RESET
18 tCLK
Start Using the Device
Figure 76. Power-Up Timing Diagram
Table 17. Power-Up Sequence Timing
SYMBOL
DESCRIPTION
MIN
tPOR
Wait after power-up until reset
216
TYP
MAX
UNIT
tCLK
tRST
Reset low width
2
tCLK
SETTING THE DEVICE FOR BASIC DATA CAPTURE
The following section outlines the procedure to configure the device in a basic state and capture data. This
procedure is intended to put the device in a data sheet condition to check if the device is working properly in the
user's system. It is recommended that this procedure be followed initially to get familiar with the device settings.
Once this procedure has been verified, the device can be configured as needed. For details on the timings for
commands refer to the appropriate sections in the data sheet. Also, some sample programming codes are added
for the ECG-specific functions.
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Analog/Digital Power-Up
Set CLKSEL Pin = 0
and Provide External Clock
fCLK = 2.048MHz
Yes
// Follow Power-Up Sequencing
External
Clock
No
Set CLKSEL Pin = 1
and Wait for Oscillator
to Wake Up
Set PDWN = 1
Set RESET = 1
Wait for 1s for
Power-On Reset
Issue Reset Pulse,
Wait for 18 tCLKs
Send SDATAC
Command
Set PDB_REFBUF = 1
and Wait for Internal Reference
to Settle
// If START is Tied High, After This Step
// DRDY Toggles at fCLK/8192
// (LP Mode with DR = fMOD/1024)
// Delay for Power-On Reset and Oscillator Start-Up
// Activate DUT
// CS can be Either Tied Permanently Low
// Or Selectively Pulled Low Before Sending
// Commands or Reading/Sending Data from/to Device
// Device Wakes Up in RDATAC Mode, so Send
// SDATAC Command so Registers can be Written
SDATAC
No
External
Reference
// If Using Internal Reference, Send This Command
¾WREG CONFIG3 0xC0
Yes
Write Certain Registers,
Including Input Short
// Set Device in HR Mode and DR = fMOD/1024
WREG CONFIG1 0x86
WREG CONFIG2 0x00
// Set All Channels to Input Short
WREG CHnSET 0x01
Set START = 1
// Activate Conversion
// After This Point DRDY Should Toggle at
// fCLK/4096
RDATAC
// Put the Device Back in RDATAC Mode
RDATAC
Capture Data
and Check Noise
// Look for DRDY and Issue 24 + n ´ 24 SCLKs
Set Test Signals
// Activate a (1mV ´ VREF/2.4) Square-Wave Test Signal
// On All Channels
SDATAC
WREG CONFIG2 0x10
WREG CHnSET 0x05
RDATAC
Capture Data
and Test Signal
// Look for DRDY and Issue 24 + n ´ 24 SCLKs
Figure 77. Initial Flow at Power-Up
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Lead-Off
Sample code to set dc lead-off with pull-up/pull-down resistors on all channels
WREG LOFF 0x13 // Comparator threshold at 95% and 5%, pull-up/pull-down resistor // DC lead-off
WREG CONFIG4 0x02 // Turn-on dc lead-off comparators
WREG LOFF_SENSP 0xFF // Turn on the P-side of all channels for lead-off sensing
WREG LOFF_SENSN 0xFF // Turn on the N-side of all channels for lead-off sensing
Observe the status bits of the output data stream to monitor lead-off status.
Right Leg Drive
Sample code to choose RLD as an average of the first three channels.
WREG RLD_SENSP 0x07 // Select channel 1—3 P-side for RLD sensing
WREG RLD_SENSN 0x07 // Select channel 1—3 N-side for RLD sensing
WREG CONFIG3 b’x1xx 1100 // Turn on RLD amplifier, set internal RLDREF voltage
Sample code to route the RLD_OUT signal through channel 4 N-side and measure RLD with channel 5. Make
sure the external side to the chip RLDOUT is connected to RLDIN.
WREG CONFIG3 b’xxx1 1100 // Turn on RLD amplifier, set internal RLDREF voltage, set RLD measurement bit
WREG CH4SET b’1xxx 0111 // Route RLDIN to channel 4 N-side
WREG CH5SET b’1xxx 0010 // Route RLDIN to be measured at channel 5 w.r.t RLDREF
PACE Detection
Sample code to select channel 5 and 6 outputs for PACE
WREG PACE b’0001 0101 // Power-up PACE amplifier and select channel 5 and 6 for PACE out
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REVISION HISTORY
NOTE: Page numbers for previous revisions may differ from page numbers in the current version.
Changes from Revision H (October 2011) to Revision I
Page
•
Added eighth Features bullet (list of standards supported) .................................................................................................. 1
•
Deleted duplicate Digital input voltage and Digital output voltage rows from Absolute Maximum Ratings table ................. 2
•
Changed parameter name of Channel Performance, Common-mode rejection ratio and Power-supply rejection ratio
parameters in Electrical Characteristics table ....................................................................................................................... 4
•
Updated BGA pin out .......................................................................................................................................................... 10
•
Updated Figure 23 .............................................................................................................................................................. 21
•
Updated description of Analog Input section ...................................................................................................................... 24
•
Updated Figure 29 .............................................................................................................................................................. 26
•
Changed description of Data Ready (DRDY) section ......................................................................................................... 32
•
Changed description of START pin in START section ....................................................................................................... 34
•
Changed conversion description in Continuous Mode section ........................................................................................... 35
•
Changed Unit column in Table 10 ...................................................................................................................................... 35
•
Changed conversion description in Single-Shot Mode section .......................................................................................... 36
•
Added power-down recommendation to bit 7 description of CHnSET: Individual Channel Settings section ..................... 50
•
Changed description of bit 5 in RESP: Respiration Control Register section .................................................................... 53
•
Corrected name of bit 6 in WCT2: Wilson Central Terminal Control Register section ....................................................... 56
•
Updated Figure 51 .............................................................................................................................................................. 57
•
Updated Figure 52 .............................................................................................................................................................. 58
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ADS1294, ADS1294R
ADS1296, ADS1296R
ADS1298, ADS1298R
SBAS459I – JANUARY 2010 – REVISED JANUARY 2012
www.ti.com
Changes from Revision G (February 2011) to Revision H
Page
•
Deleted Non-Magnetic BGA Package Features bullet ......................................................................................................... 1
•
Added (ADS1298) to High-Resolution mode and Low-Power mode subsection headers of Supply Current section in
Electrical Characteristics table .............................................................................................................................................. 6
•
Changed 3V Power Dissipation, Quiescent channel power test conditions in Electrical Characteristics table .................... 6
•
Changed 5V Power Dissipation, Quiescent channel power test conditions in Electrical Characteristics table .................... 7
•
Changed footnote 1 of BGA Pin Assignments table ........................................................................................................... 10
•
Added footnote 1 cross-reference to RLDIN, TESTP_PACE_OUT1, and TESTP_PACE_OUT in BGA Pin
Assignments table ............................................................................................................................................................... 11
•
Changed footnote 1 of PAG Pin Assignments table ........................................................................................................... 13
•
Added footnote 1 cross-reference to TESTP_PACE_OUT1, TESTP_PACE_OUT2, and RLDIN in PAG Pin
Assignments table ............................................................................................................................................................... 13
•
Changed description of AVSS and AVDD in PAG Pin Assignments table ......................................................................... 14
•
Changed title of Figure 20 .................................................................................................................................................. 18
•
Updated Equation 5 ............................................................................................................................................................ 27
•
Changed title of Table 8 ...................................................................................................................................................... 30
•
Updated Figure 45 .............................................................................................................................................................. 38
•
Changed description of STANDBY: Enter STANDBY Mode section .................................................................................. 40
•
Changed bit name for bits 5, 6, and 7 in ID register of Table 12 ....................................................................................... 44
•
Changed bit name for bits 5, 6, and 7 in ID: ID Control Register section .......................................................................... 45
•
Updated Figure 60 .............................................................................................................................................................. 64
•
Added new paragraph to Respiration section ..................................................................................................................... 70
•
Added footnote to Figure 69 ............................................................................................................................................... 73
•
Changed description of solid ceramic capacitor in Power Supplies and Grounding section .............................................. 75
•
Changed description of Connecting the Device to Bipolar (±1.5V/1.8V) Supplies section ................................................. 76
Copyright © 2010–2012, Texas Instruments Incorporated
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Product Folder Link(s): ADS1294 ADS1294R ADS1296 ADS1296R ADS1298 ADS1298R
81
PACKAGE OPTION ADDENDUM
www.ti.com
23-Nov-2011
PACKAGING INFORMATION
Orderable Device
Status
(1)
Package Type Package
Drawing
Pins
Package Qty
Eco Plan
(2)
Lead/
Ball Finish
MSL Peak Temp
(3)
(Requires Login)
ADS1294CZXGR
ACTIVE
NFBGA
ZXG
64
1000
Green (RoHS
& no Sb/Br)
SNAGCU
Level-3-260C-168 HR
ADS1294CZXGT
ACTIVE
NFBGA
ZXG
64
250
Green (RoHS
& no Sb/Br)
SNAGCU
Level-3-260C-168 HR
ADS1294IPAG
ACTIVE
TQFP
PAG
64
160
Green (RoHS
& no Sb/Br)
CU NIPDAU Level-3-260C-168 HR
ADS1294IPAGR
ACTIVE
TQFP
PAG
64
1500
Green (RoHS
& no Sb/Br)
CU NIPDAU Level-3-260C-168 HR
ADS1294RIZXGR
ACTIVE
NFBGA
ZXG
64
1000
Green (RoHS
& no Sb/Br)
SNAGCU
Level-3-260C-168 HR
ADS1294RIZXGT
ACTIVE
NFBGA
ZXG
64
250
Green (RoHS
& no Sb/Br)
SNAGCU
Level-3-260C-168 HR
ADS1296CZXGR
ACTIVE
NFBGA
ZXG
64
1000
Green (RoHS
& no Sb/Br)
SNAGCU
Level-3-260C-168 HR
ADS1296CZXGT
ACTIVE
NFBGA
ZXG
64
250
Green (RoHS
& no Sb/Br)
SNAGCU
Level-3-260C-168 HR
ADS1296IPAG
ACTIVE
TQFP
PAG
64
160
Green (RoHS
& no Sb/Br)
CU NIPDAU Level-3-260C-168 HR
ADS1296IPAGR
ACTIVE
TQFP
PAG
64
1500
Green (RoHS
& no Sb/Br)
CU NIPDAU Level-3-260C-168 HR
ADS1296RIZXGR
ACTIVE
NFBGA
ZXG
64
1000
Green (RoHS
& no Sb/Br)
SNAGCU
Level-3-260C-168 HR
ADS1296RIZXGT
ACTIVE
NFBGA
ZXG
64
250
Green (RoHS
& no Sb/Br)
SNAGCU
Level-3-260C-168 HR
ADS1298CZXGR
ACTIVE
NFBGA
ZXG
64
1000
Green (RoHS
& no Sb/Br)
SNAGCU
Level-3-260C-168 HR
ADS1298CZXGT
ACTIVE
NFBGA
ZXG
64
250
Green (RoHS
& no Sb/Br)
SNAGCU
Level-3-260C-168 HR
ADS1298IPAG
ACTIVE
TQFP
PAG
64
160
Green (RoHS
& no Sb/Br)
CU NIPDAU Level-3-260C-168 HR
ADS1298IPAGR
ACTIVE
TQFP
PAG
64
1500
Green (RoHS
& no Sb/Br)
CU NIPDAU Level-3-260C-168 HR
ADS1298RIZXGR
ACTIVE
NFBGA
ZXG
64
1000
Green (RoHS
& no Sb/Br)
Addendum-Page 1
SNAGCU
Samples
Level-3-260C-168 HR
PACKAGE OPTION ADDENDUM
www.ti.com
Orderable Device
ADS1298RIZXGT
23-Nov-2011
Status
(1)
ACTIVE
Package Type Package
Drawing
NFBGA
ZXG
Pins
64
Package Qty
250
Eco Plan
(2)
Green (RoHS
& no Sb/Br)
Lead/
Ball Finish
SNAGCU
MSL Peak Temp
(3)
Samples
(Requires Login)
Level-3-260C-168 HR
(1)
The marketing status values are defined as follows:
ACTIVE: Product device recommended for new designs.
LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.
NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design.
PREVIEW: Device has been announced but is not in production. Samples may or may not be available.
OBSOLETE: TI has discontinued the production of the device.
(2)
Eco Plan - The planned eco-friendly classification: Pb-Free (RoHS), Pb-Free (RoHS Exempt), or Green (RoHS & no Sb/Br) - please check http://www.ti.com/productcontent for the latest availability
information and additional product content details.
TBD: The Pb-Free/Green conversion plan has not been defined.
Pb-Free (RoHS): TI's terms "Lead-Free" or "Pb-Free" mean semiconductor products that are compatible with the current RoHS requirements for all 6 substances, including the requirement that
lead not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, TI Pb-Free products are suitable for use in specified lead-free processes.
Pb-Free (RoHS Exempt): This component has a RoHS exemption for either 1) lead-based flip-chip solder bumps used between the die and package, or 2) lead-based die adhesive used between
the die and leadframe. The component is otherwise considered Pb-Free (RoHS compatible) as defined above.
Green (RoHS & no Sb/Br): TI defines "Green" to mean Pb-Free (RoHS compatible), and free of Bromine (Br) and Antimony (Sb) based flame retardants (Br or Sb do not exceed 0.1% by weight
in homogeneous material)
(3)
MSL, Peak Temp. -- The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder temperature.
Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is provided. TI bases its knowledge and belief on information
provided by third parties, and makes no representation or warranty as to the accuracy of such information. Efforts are underway to better integrate information from third parties. TI has taken and
continues to take reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on incoming materials and chemicals.
TI and TI suppliers consider certain information to be proprietary, and thus CAS numbers and other limited information may not be available for release.
In no event shall TI's liability arising out of such information exceed the total purchase price of the TI part(s) at issue in this document sold by TI to Customer on an annual basis.
Addendum-Page 2
PACKAGE MATERIALS INFORMATION
www.ti.com
14-Jul-2012
TAPE AND REEL INFORMATION
*All dimensions are nominal
Device
Package Package Pins
Type Drawing
ADS1294CZXGR
NFBGA
ZXG
64
ADS1294CZXGT
ADS1294IPAGR
NFBGA
ZXG
TQFP
PAG
ADS1294RIZXGR
NFBGA
ADS1294RIZXGT
SPQ
Reel
Reel
A0
Diameter Width (mm)
(mm) W1 (mm)
K0
(mm)
P1
(mm)
W
Pin1
(mm) Quadrant
8.3
2.25
12.0
16.0
Q1
1000
330.0
16.4
64
250
330.0
16.4
8.3
8.3
2.25
12.0
16.0
Q1
64
1500
330.0
24.4
13.0
13.0
1.5
16.0
24.0
Q2
ZXG
64
1000
330.0
16.4
8.3
8.3
2.25
12.0
16.0
Q1
NFBGA
ZXG
64
250
330.0
16.4
8.3
8.3
2.25
12.0
16.0
Q1
ADS1296CZXGR
NFBGA
ZXG
64
1000
330.0
16.4
8.3
8.3
2.25
12.0
16.0
Q1
ADS1296CZXGT
NFBGA
ZXG
64
250
330.0
16.4
8.3
8.3
2.25
12.0
16.0
Q1
ADS1296IPAGR
TQFP
PAG
64
1500
330.0
24.4
13.0
13.0
1.5
16.0
24.0
Q2
ADS1296RIZXGR
NFBGA
ZXG
64
1000
330.0
16.4
8.3
8.3
2.25
12.0
16.0
Q1
ADS1296RIZXGT
NFBGA
ZXG
64
250
330.0
16.4
8.3
8.3
2.25
12.0
16.0
Q1
ADS1298CZXGR
NFBGA
ZXG
64
1000
330.0
16.4
8.3
8.3
2.25
12.0
16.0
Q1
ADS1298CZXGT
NFBGA
ZXG
64
250
330.0
16.4
8.3
8.3
2.25
12.0
16.0
Q1
ADS1298IPAGR
TQFP
PAG
64
1500
330.0
24.4
13.0
13.0
1.5
16.0
24.0
Q2
ADS1298RIZXGR
NFBGA
ZXG
64
1000
330.0
16.4
8.3
8.3
2.25
12.0
16.0
Q1
ADS1298RIZXGT
NFBGA
ZXG
64
250
330.0
16.4
8.3
8.3
2.25
12.0
16.0
Q1
Pack Materials-Page 1
8.3
B0
(mm)
PACKAGE MATERIALS INFORMATION
www.ti.com
14-Jul-2012
*All dimensions are nominal
Device
Package Type
Package Drawing
Pins
SPQ
Length (mm)
Width (mm)
Height (mm)
ADS1294CZXGR
NFBGA
ZXG
64
1000
336.6
336.6
28.6
ADS1294CZXGT
NFBGA
ZXG
64
250
336.6
336.6
28.6
ADS1294IPAGR
TQFP
PAG
64
1500
367.0
367.0
45.0
ADS1294RIZXGR
NFBGA
ZXG
64
1000
336.6
336.6
28.6
ADS1294RIZXGT
NFBGA
ZXG
64
250
336.6
336.6
28.6
ADS1296CZXGR
NFBGA
ZXG
64
1000
336.6
336.6
28.6
ADS1296CZXGT
NFBGA
ZXG
64
250
336.6
336.6
28.6
ADS1296IPAGR
TQFP
PAG
64
1500
367.0
367.0
45.0
ADS1296RIZXGR
NFBGA
ZXG
64
1000
336.6
336.6
28.6
ADS1296RIZXGT
NFBGA
ZXG
64
250
336.6
336.6
28.6
ADS1298CZXGR
NFBGA
ZXG
64
1000
336.6
336.6
28.6
ADS1298CZXGT
NFBGA
ZXG
64
250
336.6
336.6
28.6
ADS1298IPAGR
TQFP
PAG
64
1500
367.0
367.0
45.0
ADS1298RIZXGR
NFBGA
ZXG
64
1000
336.6
336.6
28.6
ADS1298RIZXGT
NFBGA
ZXG
64
250
336.6
336.6
28.6
Pack Materials-Page 2
MECHANICAL DATA
MTQF006A – JANUARY 1995 – REVISED DECEMBER 1996
PAG (S-PQFP-G64)
PLASTIC QUAD FLATPACK
0,27
0,17
0,50
48
0,08 M
33
49
32
64
17
0,13 NOM
1
16
7,50 TYP
Gage Plane
10,20
SQ
9,80
12,20
SQ
11,80
0,25
0,05 MIN
1,05
0,95
0°– 7°
0,75
0,45
Seating Plane
0,08
1,20 MAX
4040282 / C 11/96
NOTES: A. All linear dimensions are in millimeters.
B. This drawing is subject to change without notice.
C. Falls within JEDEC MS-026
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