TI ADS8201IBRGET 2.2v to 5.5v,low-power, 12-bit, 100ksps, 8-channel data acquisition system with pga and spiâ ¢ interface Datasheet

ADS8201
AD
S8
20
1
www.ti.com
SLAS534B – JULY 2009 – REVISED MAY 2010
2.2V to 5.5V, Low-Power, 12-Bit, 100kSPS, 8-Channel
Data Acquisition System with PGA and SPI™ Interface
Check for Samples: ADS8201
FEATURES
1
• Low-Power, Flexible Supply Range:
– 2.2V to 5.5V Analog Supply
– 1.32mW (100kHz, +VA = 2.2V, +VD = 2.2V)
– 4.5mW (100kHz, +VA = 5V, +VD = 5V)
• Up to 100kSPS Throughput Rate
• Excellent DC Performance:
– ±0.5 LSB typ, ±1.5 LSB max INL
– ±0.5 LSB typ, ±1.0 LSB max DNL
– ±6 LSB Offset Error at +VA =5V
– ±0.1%FS Gain Error at +VA = 5V
• Flexible Analog Inputs:
– True Differential Input
– Differential/Unipolar Input Range (0 to VREF)
– TAG Bit Output
– Programmable Averaging Function
– Onboard, Eight Single-Ended/Four
Differential Channel Mux:
– High Input Impedance
– High-Performance PGA (Gain = 1/2/4/8)
– PGA Breakout
– Auto/Manual Channel Select with Gain
– Auto/Manual Trigger
– Mixed Type Partial Scan
• Built-in Hardware Features:
– On-chip Conversion Clock (CCLK)
– Hardware/Software Reset
– Programmable Status/Polarity for BUSY/INT
• Flexible I/O:
– SPI-/ DSP™-Compatible Serial Interface
– Separate I/O Supply (2.2V to 5.5V)
– Onboard 8×1 FIFO Buffer
– SCLK up to 25MHz (VD = 5V)
...
•
234
•
•
Multi-Chip Ready and Fully Enabled:
– Global CONVST (Independent of CS)
Power-Down Mode
24-Pin 4×4 QFN Package
APPLICATIONS
•
•
•
•
•
Portable Communications
Transducer Interfaces
Portable Medical Instruments
Data Acquisition Systems
GPS Chipsets
...
DESCRIPTION
The ADS8201 is a low-power, complete on-chip data
acquisition system optimized for portable applications
that require direct connections, wide dynamic range,
and automatic operation with very low power
consumption. The device includes a 12-bit,
capacitor-based, successive approximation register
(SAR)
analog-to-digital
converter
(ADC);
a
high-performance, continuous-time programmable
gain amplifier (PGA); and a fully automatic scan,
8-to-1 multiplexer (mux) with breakout to allow for
system design flexibility.
Many other features are included to further optimize
system operation. Conversion results may be saved
in an onboard first-in/first-out (FIFO) buffer and read
out at a later time. Each channel has a gain setting
that can be loaded automatically when it is selected.
To simplify the serial port design, the ADS8201 offers
a high-speed, wide-voltage serial interface. The
ADS8201 is ideal for sensor applications (for
example, bridge sensors, pressure sensors,
accelerometers, gyrosensors, temperature sensors,
etc.) as used in gaming and navigation.
The ADS8201 is available in a 24-lead, 4x4 QFN
package, and is specified over the –40°C to +85°C
industrial temperature range.
1
2
3
4
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.
DSP is a trademark of Texas Instruments.
SPI is a trademark of Motorola Inc.
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 © 2009–2010, Texas Instruments Incorporated
ADS8201
SLAS534B – JULY 2009 – REVISED MAY 2010
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.
PACKAGE/ORDERING INFORMATION (1)
PRODUCT
MAXIMUM
INTEGRAL
LINEARITY
ERROR
(LSB)
MAXIMUM
DIFFERENTIAL
LINEARITY
(LSB)
MAXIMUM
OFFSET
ERROR
(LSB)
PACKAGELEAD
PACKAGE
DESIGNATOR
SPECIFIED
TEMPERATURE
RANGE
PACKAGE
MARKING
ADS8201I
±1.5
±1
±6
QFN-24
RGE
–40°C to +85°C
ADS8201
(1)
ORDERING
NUMBER
TRANSPORT
MEDIA,
QUANTITY
ADS8201IRGET
Tape and Reel, 250
ADS8201IRGER
Tape and Reel,
3000
For the most current package and ordering information, see the Package Option Addendum located at the end of this data sheet, or visit
the device product folder on www.ti.com.
ABSOLUTE MAXIMUM RATINGS (1)
Over operating free-air temperature range, unless otherwise noted.
Voltage
Voltage range
ADS8201I
UNIT
+INI to AGND
–0.3 to +VA +0.3
V
–INI to AGND
–0.3 to +VA +0.3
V
+VA to AGND
–0.3 to 7
V
+VD to DGND
–0.3 to 7
V
–0.3 to +0.3
V
Digital input voltage to DGND
AGND to DGND
–0.3 to VD +0.3
V
Digital output voltage to DGND
–0.3 to VD +0.3
Operating free-air temperature range, TA
–40 to +85
°C
Storage temperature range, TSTG
–65 to +150
°C
+150
°C
Junction temperature, TJ max
Package dissipation ratings: 4 × 4 QFN-16
(TJmax – TA)/qJA
Thermal impedance, qJA
(1)
46
°C/W
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 supported.
ELECTRICAL CHARACTERISTICS
At TA = –40°C to +85°C, 2.2V < VA = VREF < 5.5V, 2.2V < VD < 5.5V, fSAMPLE = 100kHz, and gain = 1, unless otherwise noted.
ADS8201I
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
0
VREF
V
AGND + 0.1
+VA – 0.1
ANALOG INPUT (IN0 to IN7)
FSR
Full-scale input range
(INI – INI–1), gain = 1
VIN
Absolute input voltage range
+INI pin
CIN
Input capacitance
With input selected
4
pF
IIL
Input leakage current
No mux switching, dc input
1
nA
Input channel crosstalk
IN = VREF/2, INI+1,
INI-1= 0 – VREF span at 1kHz
105
dB
2
Submit Documentation Feedback
V
Copyright © 2009–2010, Texas Instruments Incorporated
Product Folder Link(s): ADS8201
ADS8201
www.ti.com
SLAS534B – JULY 2009 – REVISED MAY 2010
ELECTRICAL CHARACTERISTICS (continued)
At TA = –40°C to +85°C, 2.2V < VA = VREF < 5.5V, 2.2V < VD < 5.5V, fSAMPLE = 100kHz, and gain = 1, unless otherwise noted.
ADS8201I
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
DC ACCURACY
Resolution
12
No missing codes
INL
Integral nonlinearity
DNL
Differential nonlinearity
VOS
Offset error (1)
±0.5
–1
–7.5
+1.5
LSB
±0.5
+1
LSB
3
+7.5
0.2
End-point error
Single-ended input, gain = 1
–0.1
Gain error
All gains
–0.1
Gain error drift
CMRR
Bits
–1.5
Offset error drift
GERR
Bits
12
0.05
+0.1
%
+0.1
%
0.3
Common-mode rejection ratio
At dc, PGAREF = VREF/2
mV
ppm/°C
ppm/°C
66
dB
Noise
600
mVRMS
PSS
Power-supply sensitivity
0.8
LSB
PSRR
Power-supply rejection ratio
68
dB
SAMPLING DYNAMICS
tCONV
Conversion time
10
ms
Throughput rate
100
kHz
CLOCK
fCLK
Internal conversion clock frequency
SCLK
External serial clock
3.2
4
Used as I/O clock
4.8
MHz
25
MHz
VA
V
EXTERNAL REFERENCE INPUT
VREF
Input voltage range,
VREF = (REF+ – REFGND)
RREF
Reference input resistance
2.2V ≤ VA ≤ 5.5V
2.048
360
kΩ
DIGITAL INPUT/OUTPUT
Logic family
CMOS
VIH
High-level input voltage
VD ≥ 2.2V
0.80 × (+VD)
+VD + 0.3
VIL
Low-level input voltage
VD ≥ 2.2V
–0.3
0.20 × (+VD)
IIN
Input current
VIN = +VD or DGND
CIN
Input capacitance
VOH
High-level output voltage
VD ≥ 2.2V, IOUT = 100mA
0.8 × (+VD)
VOL
Low-level output voltage
VD ≥ 2.2V, IOUT = 100mA
0
COUT
Output capacitance
CLOAD
Load capacitance
V
10
nA
5
pF
V
0.2 × (+VD)
10
Data format
V
V
pF
100
pF
V
Straight Binary
POWER SUPPLY
VD
Digital supply voltage
2.2
5.5
VA
Analog supply voltage
2.2
5.5
V
1500
mA
IQA + IQD
Supply current
IPD
Power-down current
PDISS
Power dissipation
(2)
VA = 5V
900
VA = 2.2V
600
VIN = FS at VREF = 5V,
gain = 1
0.5
2
mA
4.5
7.5
mW
VA = 5V
VA = 2.2V
mA
1.32
mW
TEMPERATURE RANGE
TA
(1)
(2)
Operating
–40
85
°C
Includes mux + PGA + ADC offset error.
With SCLK disabled.
Submit Documentation Feedback
Copyright © 2009–2010, Texas Instruments Incorporated
Product Folder Link(s): ADS8201
3
ADS8201
SLAS534B – JULY 2009 – REVISED MAY 2010
www.ti.com
PIN CONFIGURATION
IN4
1
IN5
2
IN6
3
IN7
4
IN0
PGAREF
PGAOUT
19
IN1
22
21
IN2
23
20
IN3
24
RGE PACKAGE
QFN-24
(TOP VIEW)
18
ADCIN
17
AGND
16
REFGND
15
REF
ADS8201
Thermal Pad
(Bottom Side)
(1)
(1)
10
11
12
SDO
CONVST
VD
DGND
13
9
6
SDI
BUSY/INT
8
VA
CS
14
7
5
SCLK
RST
Thermal pad should be tied to AGND.
PIN DESCRIPTIONS
PIN
4
NAME
NO.
I/O
IN4
1
I
Input channel single-ended 4 or differential pair 3
DESCRIPTION
IN5
2
I
Input channel single-ended 5 or differential pair 3
IN6
3
I
Input channel single-ended 6 or differential pair 4
IN7
4
I
Input channel single-ended 7 or differential pair 4
RST
5
I
External hardware reset
BUSY/INT
6
O
Status output. If programmed as the BUSY pin, this pin is low (default) when a conversion is in progress. If
programmed as an interrupt (INT), this pin is low for a preprogrammed duration after the end of a conversion and valid
data are to be output. The polarity of either BUSY or INT is programmable.
SCLK
7
I
Serial interface clock
CS
8
I
Chip select input for SPI interface slave select (SS)
SDI
9
I
Serial data in
SDO
10
O
Serial data out
DGND
11
I/O
Interface ground
CONVST
12
I
Starts conversion
VD
13
I
Interface supply
VA
14
I
Analog supply (+2.2VDC to +5.5VDC)
REF
15
I
External reference input
REFGND
16
I/O
Reference ground
Analog ground
AGND
17
I/O
ADCIN
18
I
ADC input
PGAOUT
19
O
Mux output. Output can be further filtered before sending to ADCIN.
PGAREF
20
I
PGA Reference
IN0
21
I
Analog channel single-ended 0 or differential pair 0
IN1
22
I
Analog channel single-ended 1 or differential pair 0
IN2
23
I
Analog channel single-ended 2 or differential pair 1
IN3
24
I
Analog channel single-ended 3 or differential pair 1
Submit Documentation Feedback
Copyright © 2009–2010, Texas Instruments Incorporated
Product Folder Link(s): ADS8201
ADS8201
www.ti.com
SLAS534B – JULY 2009 – REVISED MAY 2010
TIMING CHARACTERISTICS
All specifications typical at –40°C to +85°C, 2.2V < VA = VREF < 5.5V, and 2.2V < VD < 5.5V, unless otherwise
noted.
tD (CONVST - CONVST) = 40tOSC, Minimum
tWL (CONVST)
CONVST
N
N+1
ADC Conversion N
ADC Data Ready N
BUSY
INT
tCONV
tD (CONVST - sync)
tTP (Minimum N + 1)
2tOSC (Sampling N)
tCD
Conversion N
Conversion Delay
PGA
Settling
ADC State
PGA
Settling
Sampling N + 1
tACQ
Figure 1. Convert Timing
CONVST
N
N+1
AD Data N Ready
AD Data N + 1 Ready
INT
PGA
Settling
ADC State
Conversion Delay
Conversion N
Idle
PGA
Settling
Conversion N + 1
Conversion Delay
18tOSC + Idle
Recommended AD
Read Window
1tOSC
Recommended AD
Read Window
22tOSC
SPI Port
AD Read May Cause
Conversion Noise
Updating FIFO/ODR N
Figure 2. Read Timing
CS
SDI
D15
D13
D14
D12
D10
D11
D9
D8
D6
D7
D5
D3
D4
D2
D0
D1
tH (SDI - SCLK)
tSU (SDI - SCLK)
tSH
tSU (CS - SCLK1)
SCLK
1
2
3
tSU (Last SCLK - CS)
tSL
4
5
6
7
8
D9
D8
tD (SCLK - SDOVALID)
9
tSP
10
11
12
13
14
15
D6
D5
D4
D3
D2
D1
16
tD (SCLK - SDOINVALID)
tD (CS - SDOVALID)
SDO
D15
D14
D13
D12
tD (CS - SDO)
D11
D10
D7
D0
Figure 3. SPI Convert Timing
Submit Documentation Feedback
Copyright © 2009–2010, Texas Instruments Incorporated
Product Folder Link(s): ADS8201
5
ADS8201
SLAS534B – JULY 2009 – REVISED MAY 2010
www.ti.com
TIMING CHARACTERISTICS (continued)
Table 1. Timing Specifications
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
40
UNIT
tWL
CONVST (Convert Start) pulse width
tOSC
Oscillation time
ns
tH
Hold time
2
tSU
Setup time
10
tD
Delay time
tSH
Clock high time
10
tSL
Clock low time
10
tSP
Clock period
40
ns
tCD
Conversion delay time
18
tOSC
tACQ
Acquisition time
8.5
tOSC
tCONV
Conversion time
13.5
tOSC
tTP
Throughput time
40
tOSC
250
ns
ns
ns
20
ns
ns
ns
FUNCTIONAL BLOCK DIAGRAM
PGAOUT
ADCIN
REF+
Output Latches
and
3-State
Drivers
SAR
PGAREF
SDO
Comparator
CS
+IN[0:7]
Mux
PGA
G = 1/2/4/8
S/H
SCLK
CDAC
Conversion
and
Control Logic
SDI
CONVST
BUSY/INT
OSC
RST
AGND
REF-
6
Submit Documentation Feedback
Copyright © 2009–2010, Texas Instruments Incorporated
Product Folder Link(s): ADS8201
ADS8201
www.ti.com
SLAS534B – JULY 2009 – REVISED MAY 2010
TYPICAL CHARACTERISTICS
LINEARITY ERROR
vs CODE
DIFFERENTIAL LINEARITY ERROR
vs CODE
2
VDD = 5V
VREF = 4.9V
TA = +25°C
fSAMPLE = 100kSPS
fSCLK = 4MHz
1
0
-1
-2
0
512
1024
1536 2048 2560
Output Code
3072
3584
4096
0
512
1024
1536 2048 2560
Output Code
3072
3584
Figure 4.
Figure 5.
LINEARITY ERROR
vs CODE
DIFFERENTIAL LINEARITY ERROR
vs CODE
2
4096
2
VDD = 2.2V
VREF = 2.048V
TA = +25°C
fSAMPLE = 100kSPS
fSCLK = 4MHz
VDD = 2.2V
VREF = 2.048V
TA = +25°C
fSAMPLE = 100kSPS
fSCLK = 4MHz
1
DNL (LSB)
1
INL (LSB)
0
-1
-2
0
-1
0
-1
-2
-2
0
512
1024
1536 2048 2560
Output Code
3072
3584
4096
0
512
1024
1536 2048 2560
Output Code
3072
Figure 6.
Figure 7.
POWER-SUPPLY CURRENT
vs TEMPERATURE
POWER-DOWN CURRENT
vs TEMPERATURE
1200
3584
4096
2.0
1.8
VDD = 5V, VREF = 4.9V
Power-Down Current (mA)
Power-Supply Current (mA)
VDD = 5V
VREF = 4.9V
TA = +25°C
fSAMPLE = 100kSPS
fSCLK = 4MHz
1
DNL (LSB)
INL (LSB)
2
1000
800
VDD = 2.2V, VREF = 2.048V
600
1.6
1.4
1.2
1.0
0.8
0.6
VDD = 5V, VREF = 4.9V
VDD = 2.2V, VREF = 2.048V
0.4
0.2
400
0
-50
-25
0
25
50
Temperature (°C)
75
100
125
-50
Figure 8.
-25
0
25
50
Temperature (°C)
75
100
125
Figure 9.
Submit Documentation Feedback
Copyright © 2009–2010, Texas Instruments Incorporated
Product Folder Link(s): ADS8201
7
ADS8201
SLAS534B – JULY 2009 – REVISED MAY 2010
www.ti.com
TYPICAL CHARACTERISTICS (continued)
SINGLE-ENDED OFFSET VOLTAGE
vs TEMPERATURE
SINGLE-ENDED GAIN ERROR
vs TEMPERATURE
6
0.10
fIN = 1kHz
fSAMPLE = 91kHz
0.08
VDD = 5V, VREF = 4.9V
4
Gain Error (%)
Offset (mV)
5
3
VDD = 2.2V, VREF = 2.048V
2
VDD = 2.2V, VREF = 2.048V
0.06
0.04
VDD = 5V, VREF = 4.9V
0.02
1
0
0
-50
-25
0
25
50
Temperature (°C)
75
100
125
-50
-25
0
25
50
Temperature (°C)
Figure 11.
SIGNAL-TO-NOISE RATIO
vs TEMPERATURE
SIGNAL-TO-NOISE + DISTORTION
vs TEMPERATURE
125
70
fIN = 1kHz
fSAMPLE = 91kHz
fIN = 1kHz
fSAMPLE = 91kHz
68
68
SINAD (dB)
VDD = 5V, VREF = 4.9V
66
VDD = 2.2V, VREF = 2.048V
64
62
VDD = 5V, VREF = 4.9V
66
VDD = 2.2V, VREF = 2.048V
64
62
60
60
-50
-25
0
25
50
Temperature (°C)
75
100
125
-50
0
-25
25
50
Temperature (°C)
75
100
Figure 12.
Figure 13.
SPURIOUS-FREE DYNAMIC RANGE
vs TEMPERATURE
TOTAL HARMONIC DISTORTION
vs TEMPERATURE
85
125
-75
fIN = 1kHz
fSAMPLE = 91kHz
fIN = 1kHz
fSAMPLE = 91kHz
82
VDD = 2.2V, VREF = 2.048V
VDD = 2.2V, VREF = 2.048V
79
76
-80
THD (dB)
SFDR (dB)
100
Figure 10.
70
SNR (dB)
75
VDD = 5V, VREF = 4.9V
-85
VDD = 5V, VREF = 4.9V
73
70
-90
-50
-25
0
25
50
Temperature (°C)
75
100
125
-50
Figure 14.
8
-25
0
25
50
Temperature (°C)
75
100
125
Figure 15.
Submit Documentation Feedback
Copyright © 2009–2010, Texas Instruments Incorporated
Product Folder Link(s): ADS8201
ADS8201
www.ti.com
SLAS534B – JULY 2009 – REVISED MAY 2010
TYPICAL CHARACTERISTICS (continued)
EFFECTIVE NUMBER OF BITS
vs INPUT FREQUENCY
12
SIGNAL-TO-NOISE + DISTORTION
vs INPUT FREQUENCY
80
TA = +25°C
fSAMPLE = 91kHz
11
TA = +25°C
fSAMPLE = 91kHz
SINAD (dB)
ENOB (dB)
70
10
9
VDD = 2.2V, VREF = 2.048V
8
VDD = 5V, VREF = 4.9V
60
VDD = 2.2V, VREF = 2.048V
50
VDD = 5V, VREF = 4.9V
7
6
40
1
2
3
4
5
6
7
Input Frequency (kHz)
8
9
10
1
2
3
4
5
6
7
Input Frequency (kHz)
8
Figure 16.
Figure 17.
TOTAL HARMONIC DISTORTION
vs INPUT FREQUENCY
CROSSTALK
vs INPUT FREQUENCY
9
10
115
-60
TA = +25°C
fSAMPLE = 91kHz
TA = +25°C
fSAMPLE = 91kHz
VDD = 2.2V, VREF = 2.048V
Crosstalk(dB)
105
THD (dB)
-70
VDD = 2.2V, VREF = 2.048V
95
-80
85
VDD = 5V, VREF = 4.9V
VDD = 5V, VREF = 4.9V
75
-90
1
2
3
4
5
6
7
Input Frequency (kHz)
8
9
10
1
2
3
4
5
6
7
Input Frequency (kHz)
Figure 18.
5326
5000
8192 Conversions with
VIN = 2.5V at 5V Supply
VREF = 4.096V
fSAMPLE = 91kHz
4000
3500
Count
Count
3000
2812
2000
4237
8192 Conversions
with VIN = 1.024V at
2.2V Supply,
VREF = 2.048V,
fSAMPLE = 91kHz
3791
2500
2000
1500
1000
1000
0
10
OUTPUT CODE HISTOGRAM FOR A DC INPUT
4500
4000
3000
9
Figure 19.
OUTPUT CODE HISTOGRAM FOR A DC INPUT
6000
8
52
2
2081
2082
500
0
0
2083
2084
2085
Input Frequency (kHz)
2086
0
4
50
2037
2038
2039
0
Figure 20.
109
2040
Code
2041
2042
1
2043
Figure 21.
Submit Documentation Feedback
Copyright © 2009–2010, Texas Instruments Incorporated
Product Folder Link(s): ADS8201
9
ADS8201
SLAS534B – JULY 2009 – REVISED MAY 2010
www.ti.com
THEORY OF OPERATION
The ADS8201 is a low-power data acquisition system that includes a 12-bit successive approximation register
(SAR) analog-to-digital converter (ADC), eight-channel mux, and a first-in first-out (FIFO) buffer. The SAR
architecture is based on charge redistribution, which inherently includes a sample/hold (S/H) function.
The ADS8201 uses an internal clock to run the conversions.
The ADS8201 has eight analog inputs. The analog inputs are either single-ended or differential, depending on
the channel configuration. When a conversion is initiated, the input on these pins is sampled on the internal
capacitor array. While a conversion is in progress, the inputs are disconnected from any internal function. The
device can be programmed for manual channel selection or programmed into an auto-channel select mode that
sweeps through all +INI channels automatically.
A programmable gain amplifier (PGA) allows for a gain selection of 1, 2, 4, or 8. Individual channels can be
programmed to different gains. This feature allows the ADS8201 to be used in a wide range of applications. The
channel gain mapping feature is very useful in applications where different sensors around different
common-mode voltages must be digitized. Appropriate gain settings can also be chosen to take advantage of the
full range of the converter.
ANALOG INPUT
When the converter enters the hold mode, the voltage on the analog input channel of interest is captured on the
internal capacitor array. The input span is limited to the range of 0.1V to (VA – 0.1V). The PGA front-end
provides a high input impedance that removes the loading effect issues typically associated with high source
impedances.
Care must be taken regarding the absolute analog input voltage. To maintain converter linearity, the +IN and –IN
inputs and the span of [+IN – (–IN)] should be within the limits specified. Exceeding these ranges may cause the
converter linearity to not meet its stated specifications. To minimize noise, use low bandwidth input signals with
low-pass filters.
Care should also be taken to ensure that the output impedance of the sources driving the +IN and –IN inputs are
matched. If this matching is not observed, the two inputs could have different settling times. These different times
may result in offset error, gain error, and linearity error, which all change with temperature and input voltage.
PROGRAMMABLE GAIN AMPLIFIER (PGA)
The ADS8201 features an integrated PGA with gain options of 1, 2, 4, and 8. Each individual channel can be
configured for different gain settings depending on the application. An appropriate gain should be chosen for
each application to take advantage of the full range of the converter.
At power-up, the system settling time is approximately 40ms. This period includes the PGA turn-on time and
settling time to a 12-bit level. Once the device has been configured, the PGA settling time during channel
switching is optimized to provide a throughput of 100k samples-per-second (SPS) in auto-trigger and
auto-channel update modes.
The ADS8201 also provides a PGAOUT pin that can be used for further signal conditioning before inputting to
the ADC. If no additional conditioning is required, the PGAOUT pin should be tied to the ADCIN pin.
BIPOLAR/UNIPOLAR OPERATION
The PGAREF pin allows the ADS8201 to be operated in true differential and bipolar modes. This type of
operation is achieved by setting the PGAREF pin. If this pin is set to GND, the device operates in unipolar mode.
If the PGAREF pin is set to VREF/2, the ADS8201 operates in a bipolar mode. Both +IN and –IN inputs can swing
differentially ±VREF/2. All common-mode signals from 0V to VREF can be eliminated when the ADS8201 is
configured in differential mode. See the Application Information section for an example of a typical circuit
diagram.
10
Submit Documentation Feedback
Copyright © 2009–2010, Texas Instruments Incorporated
Product Folder Link(s): ADS8201
ADS8201
www.ti.com
SLAS534B – JULY 2009 – REVISED MAY 2010
REFERENCE
The ADS8201 requires an external reference. A clean, low-noise, well-decoupled supply voltage on this pin is
required to ensure good converter performance. A low-noise bandgap reference such as the REF3240 can be
used to drive this pin. A 10mF ceramic decoupling capacitor is required between the REF and REFGND pins of
the converter. These capacitors should be placed as close as possible to the respective device pins. The
REFGND pin should be connected by its own via to the analog ground plane of the printed circuit board (PCB)
with the shortest possible trace. The minimum reference supported by the ADS8201 is 2.048V.
CONVERTER OPERATION
The ADS8201 has an internal clock that controls the conversion rate; the frequency of this clock is 4MHz,
however, this clock can have a variance of up to 20%. The Conversion Delay System Configuration Register
(SCR) at address 0Ah can be used to offset the conversion clock variance. This register allows the conversion
delay to be programmed after conversion from a range of 0.5ms to 15ms. The default conversion delay is set to
4.5ms; however, the appropriate conversion delay can be selected to achieve maximum throughput. Unless the
device is in power-down mode, the internal clock is always on. The minimum acquisition time is 8.5 clock cycles
(this period is equivalent to 2.125ms at 4MHz) after CONVST is asserted. It takes 13.5 conversion clocks
(CCLKs), or approximately 3.375ms, to complete one conversion. The data can be clocked out during the next
4.5ms through the serial interface. Care must be taken to ensure that the next conversion is not initiated until
10ms after the first convert start is asserted.
ADC OPERATING MODE SUMMARY
Table 2 summarizes the ADC operating modes for the ADS8201.
Table 2. ADC Operating Modes
ADC
OPERATING
MODE
0 (000)
ADC
TRIGGER
CHANNEL
CONTROL
DELAY MUX
MULTI-SCAN
AUTO PD
Idle
(no trigger)
N/A
N/A
N/A
N/A
ADC idle
1 (001b)
MODE DESCRIPTION
Reserved
2 (010b)
Manual
trigger
Manual
Off
N/A
Off
Manual trigger with manual-channel
3 (011b)
Manual
trigger
Manual
On
N/A
Off
Manual trigger with manual-channel and
delay mux
4 (100b)
Auto trigger
Manual
On
N/A
Off
Auto trigger with manual-channel
5 (101b)
Auto trigger
Auto
increment
N/A
Single scan
Off
Auto trigger with auto-channel and
single-scan
6 (110b)
Auto trigger
Auto
increment
N/A
Multi-scan
Off
Auto trigger with auto-channel and
multi-scan
7 (111b)
Reserved
Submit Documentation Feedback
Copyright © 2009–2010, Texas Instruments Incorporated
Product Folder Link(s): ADS8201
11
ADS8201
SLAS534B – JULY 2009 – REVISED MAY 2010
www.ti.com
MANUAL TRIGGER (See ADC Trigger SCR, Address 08h, Bits[2:0])
Manual-Trigger mode (Modes 2 and 3) can be selected by writing to the ADC Trigger SCR (see the SCR
Register Map). In these modes, it is required to issue a convert start (CONVST) pulse through the CONVST pin
or an ADC read command if bit 0 of the ADC SCR is set to '1' to allow a conversion to initiate through the serial
interface. CCR[0:3] can be used to configure each channel according to the specific application requirements.
For Mode 3, see the Delay Mux Description section for details. Table 3 lists the selection options for manual
channel selection.
Table 3. Manual Channel Selection (1)
SELECTION OPTION
BIT SETTINGS
ADC SCR, bit D[1] = '1'; FIFO buffer enabled (as shown in Figure 22)
Delay mux select enabled (1)
ADC SCR, bit D[1] = '0'; FIFO buffer disabled (as shown in Figure 22)
ADC SCR, bit D[1] = '1'; FIFO buffer enabled (as shown in Figure 22)
Delay mux select disabled (1)
(1)
ADC SCR, bit D[1] = '0'; FIFO buffer disabled (as shown in Figure 22)
See ADC Trigger SCR, bits D[2:0].
Mode 2 (manual trigger with manual-channel update) provides complete control over the ADS8201 timing. The
user controls when to issue a CONVST and when to read the output data. A switch can be made to any channel
without following any particular sequence. The device can also be configured to enable or disable the FIFO
buffer in this mode.
Mode 3 (manual trigger with manual-channel update and delay mux) allows the ADS8201 to switch the mux to
the next input channel after the current sampling is complete. This capability maximizes the time required for the
PGA to settle for the next channel and subsequently provides faster throughput. See Figure 22 and Figure 25 for
timing details. This increased throughput is the key difference between this mode and Mode 2. The delay mux
feature allows for full 100kSPS throughput, in spite of being in manual trigger and manual channel update mode.
There are two ways to set up the delay mux in this mode. If using the following sequence, then data from first
channel are not repeated:
1. The first channel of interest is set.
2. Mode 3 is selected.
3. The second channel of interest is set.
4. The CONVST pin is asserted.
However, if the second channel of interest is set after the CONVST pin is asserted, then the first conversion
result should be treated as a dummy conversion because the conversion result from the first channel is repeated
twice. Subsequent channels should be selected before asserting the next CONVST in order to achieve the
benefit of the delay mux feature.
CONVST
N
N+1
ADC Conversion N
ADC Data Ready N
BUSY
INT
Sampling N
ADC State
PGA
Settling
Channel Select CCR
Sampling N + 1
Conversion N
Conversion Delay
Idle
CH1
PGA
Settling
Host Writes CH2
Mux Channel Update (as Host Write)
Mux Channel (Mode 2)
CH1 (N)
CH2 (N + 1)
Mux Channel Update (Delayed)
Mux Channel (Mode 3)
CH1 (N + 1)
CH2 (N + 2)
Figure 22. Mode 2, Mode 3 Timing
12
Submit Documentation Feedback
Copyright © 2009–2010, Texas Instruments Incorporated
Product Folder Link(s): ADS8201
ADS8201
www.ti.com
SLAS534B – JULY 2009 – REVISED MAY 2010
AUTO TRIGGER (See ADC Trigger SCR, Address 08h, Bits[2:0])
Auto-trigger mode can be selected by writing to the ADC Trigger SCR (see the SCR Register Map). In
Auto-Trigger (Modes 4, 5, and 6), Auto-Channel (Modes 5 and 6) or Manual-Channel (Mode 4) selection must be
enabled after all the channels have been configured according to the specific application.
In Auto-Trigger with Auto-Channel Update and Single-Scan mode (Mode 5), the internal device logic triggers
conversions and all selected channels are converted sequentially. After the completion of the selected channel
conversions, an SPI command must be issued to initiate the next scan event. In this mode, the FIFO buffer can
be enabled or disabled. If the FIFO buffer is enabled and the next scan event is initiated, the contents of the
FIFO buffer are overwritten. Ensure that all results from the FIFO buffer have been read before issuing the
command to start the next scan event. This mode is useful for applications where an external source triggers the
scan event; however, the trigger is not periodic.
In Auto-Trigger with Auto-Channel Update and Multi-Scan mode (Mode 6), the internal device logic triggers
conversions and all selected channels are converted sequentially. In this mode, if the FIFO buffer is disabled,
and the ADS8201 continues to trigger conversions for the selected channels in a cyclical mode until an SPI
command is sent to stop the conversion. For example, if channel 4 is selected as the starting channel number,
the ADS8201 converts channels 4, 5, 6, 7, 4, 5, 6, 7, etc., until this mode is disabled. If the FIFO buffer is
enabled and Interrupt SCR, bit D[1] is set, the ADS8201 issues a scan data ready interrupt. It is important to note
that in Mode 6, the FIFO buffer contents must be read when the buffer is full (eight conversions = complete);
otherwise, subsequent conversions will overwrite the data in the FIFO buffer. This mode is useful when
continuous conversion of the input signals across single or multiple channels is required. Figure 26 illustrates the
timing for a shared single-scan and multiple-scan mode event.
In Auto-trigger with Manual Channel Update mode (Mode 4), the user must select the next channel. In this mode,
the delay mux feature is always enabled. Table 4 and Table 5 summarize the selection options for auto channel
update and manual channel update, respectively. This mode is useful when the user wants to have flexibility in
the channel selection and does not want to use consecutive channels. The delay-mux feature provides full
100kSPS speed in spite of using manual channel update mode.
There are two ways to set up the delay mux in this mode. If using the following sequence, then data from first
channel are not repeated:
1. The first channel of interest is set.
2. Mode 4 is selected.
3. The second channel of interest is set within 10µs after setting Mode 4.
4. The CONVST pin is asserted.
However, if the second channel of interest is not set within 10µs after triggering the delay mux mode, then the
first conversion result should be treated as a dummy conversion because the conversion result from the first
channel is repeated twice.
Table 4. Auto Channel Update (1)
SELECTION OPTION
BIT SETTINGS
ADC SCR, bit D[1] = '1'; FIFO buffer enabled (as shown in Figure 23)
Single-Scan Mode (Mode 5) (1)
ADC SCR, bit D[1] = '0'; FIFO buffer disabled (as shown in Figure 23)
ADC SCR, bit D[1] = '1'; FIFO buffer enabled (as shown in Figure 24)
Multi-Scan Mode (Mode 6) (1)
(1)
ADC SCR, bit D[1] = '0'; FIFO buffer disabled (as shown in Figure 24)
See ADC Trigger SCR:D[2:0].
Table 5. Manual Channel Update (1)
(1)
SELECTION OPTION
BIT SETTINGS
Delay mux select (Mode 4)
(This is the only option with auto channel
select mode and manual trigger)
ADC SCR, bit D[1] = '0' ; FIFO buffer disabled (as shown in Figure 25)
ADC SCR, bit D[1] = '1'; FIFO buffer enabled (as shown in Figure 25)
See ADC Trigger SCR, bits D[2:0].
Submit Documentation Feedback
Copyright © 2009–2010, Texas Instruments Incorporated
Product Folder Link(s): ADS8201
13
ADS8201
SLAS534B – JULY 2009 – REVISED MAY 2010
www.ti.com
40tOSC
Auto Trigger
Conv. CH5
Conv. CH6
Conv. CH7
BUSY
Auto Trigger Halted After Scan
INT
Set to ScanData Ready INT
Channel Select CCR
CH5
Auto Mux Channel
CH5
CH6
CH7
CH4
40tOSC
ADC State
Figure 23. Mode 5 Timing
40tOSC
Auto Trigger
Conv. CH5
Conv. CH6
Conv. CH7
Conv. CH5
Conv. CH6
BUSY
Set to ScanData Ready INT
Next Scan Starts Automatically
INT
CH5
Auto Mux Channel
CH5
CH6
CH7
CH5
CH6
CH7
Figure 24. Mode 6 Timing
40tOSC
Auto Trigger
BUSY
tSU = 2tOSC, Minimum
Channel Select CCR
CH5
Manual Mux Channel
CH3
CH4
CH2
CH5
CH3
CH6
CH1
CH2
CH2
CH6
CH1
Set to AdData Ready INT
INT
Figure 25. Mode 4 Timing
Auto Trigger, Auto Channel Select with FIFO Enabled
Mux Channel Select (MS)
CH 1
CH 2
CH 3
CH 4
CH 5
CH 6
BUSY (MS)
0
1
2
3
4
5
6
7
BUSY (SS)
0
1
2
3
4
5
6
7
Mux Channel Select (SS)
CH 1
CH 2
CH 3
CH 4
CH 5
CH 1
CH 7
0
2
CH 3
CH 4
CH 5
CH 6
3
4
5
6
7
No conversions until next SCR0 write
CH 6
CH 7
FIFO Full
INT (C)
1
CH 2
INT remains low until CS is issued by host (SCR0 D7 = 1)
FIFO Empty
CS (C)
NOTE: MS: Multi-Scan Mode
SS: Single-Scan Mode
C: Signal common to both SS and MS
Figure 26. Single-Scan/Multiple-Scan Mode Event with FIFO Buffer Enabled
14
Submit Documentation Feedback
Copyright © 2009–2010, Texas Instruments Incorporated
Product Folder Link(s): ADS8201
ADS8201
www.ti.com
SLAS534B – JULY 2009 – REVISED MAY 2010
CONVERSION START
A conversion is initiated by bringing the CONVST pin low for a minimum of 40ns. After the minimum requirement
has been met, the CONVST pin can be brought high. CONVST acts independently of CS, so it is possible to use
one common CONVST for applications that require simultaneous sample/hold events. The ADS8201 requires 8.5
conversion clock (CCLK) cycles for acquisition and 13.5 CCLK edges to complete a conversion. The conversion
time is equivalent to approximately 3.375ms with a 4MHz internal clock. The minimum time between two
consecutive CONVST signals is 40 CCLKs, or approximately 10ms.
Conversion can also be initiated without using the CONVST pin if the device is properly programmed (ADC SCR,
bit D[0] = '1'). In this case, an ADC read command must be issued. The conversion start is then issued through
the SPI interface. When the converter is configured in Auto-Trigger mode, the next conversion automatically
starts 18 CCLKs after the end of a conversion. These 18 conversion clocks are used as the data acquisition time
as well as the PGA settling time. The PGA must settle to a 12-bit level. In this case, the time to complete one
acquisition and conversion cycle is exactly 22 CCLKs.
BUSY/INT PIN DESCRIPTION
BUSY Pin Functionality
The BUSY/INT pin can be programmed as BUSY by configuring the ADC System Configuration Register (ADC
SCR, bit D[2] = '1') . When the status pin is programmed as BUSY and the polarity is set as active low, this pin
works in the following manner:
• In Manual-Trigger mode: the BUSY output goes low up to 8.5 CCLKs after CONVST goes low. BUSY stays
low throughout the conversion process and returns high when the conversion completes. See Figure 1
through Figure 3 for detailed timing diagrams.
• In Auto-Trigger mode: the BUSY output goes low for 13.5 CCLKs. See Figure 1 through Figure 3 for
detailed timing diagrams. It is important to note that if BUSY/INT pin is programmed as BUSY, then bits
D[3:0] of the Interrupt SCR (address 06h) are inactive. Those interrupts only take effect when the BUSY/INT
pin is programmed as INT.
INT Pin Functionality
The BUSY/INT pin can be programmed as INT by configuring the ADC System Configuration Register (ADC
SCR, bit D[2] = '0'). The interrupt can be programmed to be edge-triggered or level-triggered by configuring the
ADC SCR, bit D[4]. This option is only available when the pin is configured as INT. For the INT pin to be active,
the interrupt SCR must be configured with the type of interrupt required for the specific application. This
procedure can be done by configuring one of the four bits, D[3:0], of the Interrupt SCR (address 06h). For
example, if the interrupt function is desired after the ADC data are ready, set the Interrupt SCR, bit D[0] = '1').
If the FIFO buffer is disabled and Interrupt SCR, bit D[0] is set, the ADS8201 issues an interrupt pulse after the
end of a conversion.
If the FIFO buffer is enabled and Interrupt SCR, bit D[2] is set, the ADS8201 issues an interrupt pulse after the
FIFO buffer is full.
POWER-DOWN MODE
The ADS8201 has a comprehensive, built-in, power-down feature. Contents of the configuration register are not
affected when in power-down mode. Power-down mode can be activated by setting the Interrupt SCR, bit D[7] =
'1'. Care must be taken to ensure that the ADC is in idle mode before writing to the Interrupt SCR. When the
device is in power-down mode, every block except the interface is in a power-down state. The analog blocks
receive no bias currents and the internal oscillator is turned off. In this mode, power dissipation falls from 900mA
to < 1mA in 2ms. The wake-up time from power-down mode is 40ms. Power-down or power-on status of the ADC
can be read through the Status SCR, bit D[0]. To bring the device out of power down, set the Interrupt SCR
(address 06h), bit D[7] = '0'.
Submit Documentation Feedback
Copyright © 2009–2010, Texas Instruments Incorporated
Product Folder Link(s): ADS8201
15
ADS8201
SLAS534B – JULY 2009 – REVISED MAY 2010
www.ti.com
READING CONVERSION RESULTS
The conversion result is available to the input of the Output Data Register (ODR) at the end of the conversion,
and presented to the output of the Output Register at the next falling edge of CS. The host processor can then
shift the data out through the SDO pin at any time except during the quiet zone. The quiet zone is 18 CCLKs
after BUSY goes high, If BUSY is programmed as active low.
Be careful not to place the falling edge of CS at the precise moment that the conversion ends (by default, the
end of conversion is when BUSY goes high); otherwise, the conversion data could be corrupted. The falling edge
of CS should be at least one CCLK either before or after the end of conversion. If CS is placed before the end of
conversion, the previous conversion result is read. If CS is placed after the end of conversion, the current
conversion result is read.
The conversion result is represented by 12-bit data in straight binary format, as shown in Table 6. Therefore, it is
normally clocked out within 12 SCLKs. In order to read the averaging bits and the TAG bits, 20 CLK cycles must
be provided. See the TAG Mode section for more details. Data output from SDO are left-aligned and MSB first.
SDO remains low until CS goes high again.
The serial output (SDO) is active when CS is low. The rising edge of CS puts the SDO output into a 3-state
mode. Note that whenever SDO is not in a 3-state mode (that is, when CS is low and SCLK is running), a portion
of the conversion result shows up on the SDO pin. The number of bits that appear depends on how many SCLKs
are supplied. The exception is that SDO outputs all 1's during the cycle immediately after any reset event
(hardware or software) occurs.
Table 6. Ideal Input Voltages and Output Codes
DESCRIPTION
ANALOG VALUE
Full-Scale Range
VREF
Least Significant Bit
(LSB)
VREF/4096
Full-Scale
Midscale
DIGITAL OUTPUT
STRAIGHT BINARY
BINARY CODE
HEX CODE
VREF – 1LSB
1111 1111 1111
FFFF
VREF/2
1000 0000 0000
8000
Midscale – 1LSB
VREF/2 – 1LSB
0111 1111 1111
7FFF
Zero
0V
0000 0000 0000
0000
TAG MODE
The ADS8201 has a TAG feature that shows which channel the converted result comes from. An address bit that
indicates the conversion result channel number is added after the LSB of the SDO readout. There are four TAG
bits: the first three identify the channel and the fourth identifies either single-ended or differential operating mode.
To read the TAG bits, 20 CLK cycles must be provided; see Figure 30. If the TAG bits do not need to be read,
only 16 CLK cycles should be provided.
AVERAGING MODE
The ADS8201 offers multiple averaging options for applications that may require greater than 12-bit resolution.
This feature allows for better noise performance by a factor of 1/√Number of Samples. The result is output as a
maximum of 14-bit resolution. Bits D[7:5] of the ADC SCR (address 05h) can be used to select different
averaging options. Two distinct averaging features, fast averaging and accurate averaging, are available:
• Fast Averaging: An average of 4,8, or 16 results can be selected to increase overall resolution to a 13-bit or
14-bit level. In Fast Averaging, after the first conversion is complete (approximately 4ms), the next conversion
starts immediately without the 6ms delay for PGA settling. This mode should be used when the input to the
PGA is stable and is within the 12-bit level.
• Slow Averaging: An average of 4, 8, or 16 results can be selected to increase output accuracy compared to
the fast averaging mode. In Slow Averaging mode, each conversion requires 10ms. This mode should be
used when the input to the PGA is not stable.
16
Submit Documentation Feedback
Copyright © 2009–2010, Texas Instruments Incorporated
Product Folder Link(s): ADS8201
ADS8201
www.ti.com
SLAS534B – JULY 2009 – REVISED MAY 2010
FIFO BUFFER DESCRIPTION
The ADS8201 offers a first-in/first out (FIFO) buffer that allows the user to store up to eight independent
conversion results. The FIFO buffer can be enabled or disabled by setting bit D[1] of the ADC SCR. To extract
the data from the FIFO buffer, CS must be enabled for every conversion result. As an example, if all eight
conversion results are to be extracted from the FIFO buffer, CS must be asserted low eight times. During the
time that CS is low, there is the option to provide as many CLK cycles as desired to extract the data of interest. If
12 CLKs are provided, only the 12-bit conversion result is extracted. If the the TAG information is to be extracted
as well, then 20 CLKs must be provided. See Figure 30 for details on the optional bits available. The functionality
of the FIFO buffer can vary depending on the mode selected.
1. Auto-Trigger and Auto Channel Select mode: In this mode, whether or not the FIFO buffer is seen as full
is defined by the number of channels in the specific scan event. For example, if channel 3 is chosen as the
starting channel number and all channels are in single-ended mode, once the conversion is complete for
channels 3, 4, 5, 6, and 7, a scan data ready interrupt is issued. Note that there are only five results in the
buffer. If a multi-scan event is enabled (Mode 6 of the ADC SCR), conversions are initiated in a cyclical
manner. If a single-scan event is enabled, the devices wait for a CONVST pulse before starting the next
conversion.
2. Auto-Trigger and Manual Channel Select mode: This mode acts in a similar manner to the previous mode,
except that the next conversion channel must be manually selected.
3. Manual-Trigger and Manual Channel Select mode: In this mode, eight conversions must be completed
before a FIFO buffer full interrupt is issued. This mode provides the flexibility to choose any sequence of
channels for conversion.
INTERRUPT DESCRIPTION
The ADS8201 offers multiple interrupts for various user-defined options. The Interrupt SCR defines the various
interrupts available in the ADS8201.
1. FIFO Buffer Not Empty Interrupt: If this interrupt is enabled (Interrupt SCR, bit D[3] = '1'), the ADS8201
generates an interrupt if the FIFO buffer is not empty. In applications where the CPU can allocate additional
processing time, use of this interrupt is recommended to improve the system throughput.
2. FIFO Buffer Full Interrupt: If this interrupt is enabled (Interrupt SCR, bit D[2] = '1'), the ADS8201 generates
an interrupt if the FIFO buffer is full. For applications where the CPU is processing multiple tasks, this
interrupt is recommended because it requires minimum processing power.
3. Scan Data Ready Interrupt: If this interrupt is enabled (Interrupt SCR, bit D[1] = '1'), the ADS8201
generates an interrupt when scan data are ready. This interrupt is only applicable in Auto-trigger and Auto
channel select modes, and tells the user when the scan event is complete for the selected channels. For
example, in single-ended configuration, if channel 3 is selected as the starting channel number, the interrupt
is issued after conversion is complete for channels 3, 4, 5, 6, and 7.
4. ADC Data Ready Interrupt: If this interrupt is enabled (Interrupt SCR, bit D[0] = '1'), the ADS8201 issues an
interrupt after the first 12 bits of conversion data are available, if averaging is disabled. If averaging is
enabled, the interrupt is issued after all conversions required for averaging are complete.
DELAY MUX DESCRIPTION
The Delay Mux feature is only available in the following modes:
• Manual-trigger with manual channel update (Mode 3 of ADC Trigger SCR)
• Auto-trigger with manual channel update (Mode 4 of ADC Trigger SCR)
This feature allows the ADS8201 to switch the mux to the next input channel after the current sampling is
complete. This capability maximizes the time required for the PGA to settle for the next channel and
subsequently provides faster throughput. Care must be taken, however, to ensure that the PGA does not settle
to the 12-bit level for throughput less than 10ms. See Figure 22 and Figure 25 for timing details. In this mode, the
mux channel is changed after the completion of next sampling period.
Submit Documentation Feedback
Copyright © 2009–2010, Texas Instruments Incorporated
Product Folder Link(s): ADS8201
17
ADS8201
SLAS534B – JULY 2009 – REVISED MAY 2010
www.ti.com
RESET OPERATION
The ADS8201 can be reset in two ways: hardware reset and software reset. A hardware reset can be asserted
via the RST pin. A software reset can be asserted through the serial interface by writing AAh to the Reset SCR
(address 09h). While hardware reset can be asserted at any time, software reset cannot be initiated if the device
is in power-down mode. As long as the device is in any other of the ADC operating modes, a software reset can
be issued. Once the reset is issued, the device comes back up in Mode 2 configuration. Once the reset is issued,
all digital logic and configuration registers are set to the respective default states (see the Channel Configuration
Map and System Configuration Map sections for default values). Any conversion in process is aborted as soon
as a reset is issued. Data stored in the FIFO buffer are also reset. The channels and system registers must be
reconfigured.
18
Submit Documentation Feedback
Copyright © 2009–2010, Texas Instruments Incorporated
Product Folder Link(s): ADS8201
ADS8201
www.ti.com
SLAS534B – JULY 2009 – REVISED MAY 2010
DEVICE CONFIGURATION
WRITING TO/READING FROM THE REGISTERS
The ADS8201 can be configured by writing to a total of 10 configuration registers: five channel configuration
registers (CCRs) and five system configuration registers (SCRs). The Interrupt and Status SCRs provide the
status of various interrupts. Figure 27 illustrates a state diagram for the ADC modes. Figure 28 through Figure 30
show the details of the Register Read, Register Write, and ADC Read operations, respectively. Table 7
summarizes the register addresses. It is important to note that except for registers 04h, 08h, and 09h (which can
be accessed from any mode), all other registers must be accessed from ADC idle mode only.
ADC Idle
Power-Up/
Hardware Reset/
Software Reset
For Every
Single-Scan Event
Mode 5
Mode 2
Modes
3/4/6
Figure 27. ADC Mode State Diagram
DATA
ADDRESS
SDIN
0
1
A3
A2
A1
A0
X
X
X
X
X
X
X
X
X
X
SDOUT
X
X
X
0
0
0
0
0
D7
D6
D5
D4
D3
D2
D1
D0
Figure 28. Register Read
DATA
ADDRESS
SDIN
1
0
A3
A2
A1
A0
X
X
D7
D6
D5
D4
D3
D2
D1
D0
SDOUT
X
X
X
0
0
0
0
0
X
X
X
X
X
X
X
X
Figure 29. Register Write
Submit Documentation Feedback
Copyright © 2009–2010, Texas Instruments Incorporated
Product Folder Link(s): ADS8201
19
ADS8201
SLAS534B – JULY 2009 – REVISED MAY 2010
www.ti.com
DATA
ADDRESS
SDIN
0
0
X
X
X
X
X
X
X
X
X
X
X
X
X
X
TAG
SDOUT
D15
D14
D13
D12
D11
D10
D9
D8
D7
D6
D5
D4
D3
D2
D1
=0
D0
=0
Averaging Bits
Channel
Address
SE/
Diff
Optional
Figure 30. ADC Read
Table 7. Register Addresses
20
REGISTER
A3
A2
A1
A0
Channel 0/1 CCR
0
0
0
0
Channel 2/3 CCR
0
0
0
1
Channel 4/5 CCR
0
0
1
0
Channel 6/7 CCR
0
0
1
1
Channel Select CCR
0
1
0
0
ADC SCR
0
1
0
1
Interrupt SCR
0
1
1
0
Status SCR
0
1
1
1
ADC Trigger SCR
1
0
0
0
RESET SCR
1
0
0
1
Conversion Delay SCR
1
0
1
0
Submit Documentation Feedback
Copyright © 2009–2010, Texas Instruments Incorporated
Product Folder Link(s): ADS8201
ADS8201
www.ti.com
SLAS534B – JULY 2009 – REVISED MAY 2010
CHANNEL CONFIGURATION REGISTER (CCR) MAP
Channel 0/1 CCR (Address 00h)
D[7:6]
Not used
[0:0]
D[5:4]
Channel 1 Gain Single-Ended
00:
01:
10:
11:
D[3]
G = 1 (default)
G=2
G=4
G=8
Channel 0 Differential Odd/Even Polarity
0: Even polarity (default)
1: Odd polarity
D[2]
Channels 0/1 Single-Ended/Differential
0 : Ch0/1 Single-ended (default)
1: Ch0/1 Differential
D[1:0]
Channel 0 Gain
00:
01:
10:
11:
G = 1 (default)
G=2
G=4
G=8
Channel 2/3 CCR (Address 01h)
D[7:6]
Not used
[0:0]
D[5:4]
Channel 3 Gain Single-Ended
00:
01:
10:
11:
D[3]
G = 1 (default)
G=2
G=4
G=8
Channel 2 Differential Odd/Even Polarity
0: Even polarity (default)
1: Odd polarity
D[2]
Channels 2/3 Single-Ended/Differential
0 : Ch2/3 Single-ended (default)
1: Ch2/3 Differential
D[1:0]
Channel 2 Gain
00:
01:
10:
11:
G = 1 (default)
G=2
G=4
G=8
Submit Documentation Feedback
Copyright © 2009–2010, Texas Instruments Incorporated
Product Folder Link(s): ADS8201
21
ADS8201
SLAS534B – JULY 2009 – REVISED MAY 2010
www.ti.com
Channel 4/5 CCR (Address 02h)
D[7:6]
Not used
[0:0]
D[5:4]
Channel 5 Gain Single-Ended
00:
01:
10:
11:
D[3]
G = 1 (default)
G=2
G=4
G=8
Channel 4 Differential Odd/Even Polarity
0: Even polarity (default)
1: Odd polarity
D[2]
Channels 4/5 Single-Ended/Differential
0 : Ch4/5 Single-ended (default)
1: Ch4/5 Differential
D[1:0]
Channel 4 Gain
00:
01:
10:
11:
G = 1 (default)
G=2
G=4
G=8
Channel 6/7 CCR (Address 03h)
D[7:6]
Not used
[0:0]
D[5:4]
Channel 7 Gain Single-Ended
00:
01:
10:
11:
D[3]
G = 1 (default)
G=2
G=4
G=8
Channel 6 Differential Odd/Even Polarity
0: Even polarity (default)
1: Odd polarity
D[2]
Channels 6/7 Single-Ended/Differential
0 : Ch6/7 Single-ended (default)
1: Ch6/7 Differential
D[1:0]
Channel 6 Gain
00:
01:
10:
11:
22
G = 1 (default)
G=2
G=4
G=8
Submit Documentation Feedback
Copyright © 2009–2010, Texas Instruments Incorporated
Product Folder Link(s): ADS8201
ADS8201
www.ti.com
SLAS534B – JULY 2009 – REVISED MAY 2010
CHANNEL SELECT REGISTER MAP
Channel Select Register (Address 04h)
D[7:3]
Not used
[0:0]
D[2:0]
Select Mux Input Channel/Start Channel Number if in Auto-Scan Mode
000:
001:
010:
011:
100:
101:
110:
111:
Channel 0 (default)
Channel 1
Channel 2
Channel 3
Channel 4
Channel 5
Channel 6
Channel 7
SYSTEM CONFIGURATION REGISTER (SCR) MAP
ADC SCR (Address 05h)
D[7:5]
Average Select
000:
001:
010:
011:
100:
101:
110:
111:
D[4]
No average (default)
Fast average of four results
Fast average of eight results
Fast average of 16 results
No average
Accurate average of four results
Accurate average of eight results
Accurate average of 16 results
Interrupt Select
0: Level triggered (default)
1: Edge triggered. Period of pulse is 250ns.
D[3]
BUSY/INT Level
0: Active low (default)
1: Active high
D[2]
BUSY/INT Select
0 : INT (default)
1: BUSY
D[1]
FIFO Buffer Enable
0: FIFO buffer disabled (default)
1: FIFO buffer enabled
D[0]
RD/CONVST Trigger
0 : Issue CONVST from the pin (default)
1: Convert start is issued through the SPI after the first read of the ADC. Ignore the first read.
Submit Documentation Feedback
Copyright © 2009–2010, Texas Instruments Incorporated
Product Folder Link(s): ADS8201
23
ADS8201
SLAS534B – JULY 2009 – REVISED MAY 2010
www.ti.com
Interrupt SCR (Address 06h)
D[7]
Power-Down Control
0: Normal conversion mode (default)
1: Power-down idle mode
D[6:4]
Always Reads '0'
D[3]
FIFO Buffer Not Empty Interrupt
Read 0: Interrupt not generated (default)
Read 1: Interrupt generated when FIFO buffer is not empty
Write 0: Disable interrupt
Write 1: Enable interrupt
D[2]
FIFO Buffer Full Interrupt
Read 0: Interrupt not generated (default)
Read 1: Interrupt generated when FIFO buffer is full
Write 0: Disable interrupt
Write 1: Enable interrupt
D[1]
Scan Data Ready Interrupt
Read 0: Interrupt not generated (default)
Read 1: Interrupt when scan data are ready. Only applicable in auto channel and auto-trigger mode.
Write 0: Disable interrupt
Write 1: Enable interrupt
D[0]
ADC Data Ready Interrupt
Read 0: Interrupt not generated (default)
Read 1: Interrupt generated when ADC data are ready.
Write 0: Disable interrupt
Write 1: Enable interrupt
Status SCR (Address 07h)
D[7:4]
FIFO Buffer Level: Number of Entries
D[3]
FIFO buffer Not Empty
0: FIFO buffer empty
1: FIFO buffer not empty
D[2]
FIFO Buffer Full
0: FIFO buffer not full
1: FIFO buffer full
D[1]
Scan Data Ready
0: Not ready
1: Ready
D[0]
ADC Data Ready
0: Not ready
1: Ready
ADC Trigger SCR (Address 08h)
D[7:3]
Not used
D[2:0]
ADC Trigger
000:
001:
010:
011:
100:
101:
110:
111:
ADC idle
Reserved
Manual trigger with manual channel update (default)
Manual trigger with manual channel and delay mux
Auto-trigger with manual channel update. Delay mux is always enabled.
Auto-trigger with auto channel update in single-scan event mode.
Auto-trigger with auto channel update in multi-scan event mode.
Reserved
Reset SCR (Address 09h)
D[7:0]
Device Reset
Default = 00
Read : Always 00
Write: AAh to reset the device
24
Submit Documentation Feedback
Copyright © 2009–2010, Texas Instruments Incorporated
Product Folder Link(s): ADS8201
ADS8201
www.ti.com
SLAS534B – JULY 2009 – REVISED MAY 2010
Conversion Delay SCR (Address 0Ah)
D[7:3]
Not Used
D[2:0]
Select PGA Delay After Conversion
D[2:0]
ACQUISITION TIME
(ms)
ADC CONVERSION
TIME (ms)
CONVERSION DELAY
(ms)
ADC THROUGHPUT
(ms)
000
2.125
3.375
0.5
6
001
2.125
3.375
2.5
8
010
2.125
3.375
4.5
10
011
2.125
3.375
6.5
12
100
2.125
3.375
8.5
14
101
2.125
3.375
10.5
16
110
2.125
3.375
12.5
18
111
2.125
3.375
14.5
20
Submit Documentation Feedback
Copyright © 2009–2010, Texas Instruments Incorporated
Product Folder Link(s): ADS8201
25
ADS8201
SLAS534B – JULY 2009 – REVISED MAY 2010
www.ti.com
APPLICATION INFORMATION
Figure 31 illustrates an example precision positioning application.
2.048V to 5V
10mF
2.2V
to 5V
1mF
240pF
1 mF
Gyro
Sensor
VD
VA
REF
REFGND
PGAOUT
AGND
VOUT
1.35V ±0.2V
ADCIN
1kW
DGND
PGAREF
ADS8201
VREF
1.35V
SDO
IN0
1.05kW
G=8
G=4
1V IN1
Differential
Pair
SDI
G=2
IN2
CS
G=1
Z
RST
IN6
Y
IN7
IN5
IN4
IN3
BUSY/INT
3kW
Microprocessor
CONVST
SCLK
(1)
X
Single-Ended
Accelerometer
(1)
X = 100mV < VIN < VA –100mV; Y = 100mV < VIN < VA/2; Z = 100mV < VIN < VA/4
Figure 31. Precision Positioning Application
26
Submit Documentation Feedback
Copyright © 2009–2010, Texas Instruments Incorporated
Product Folder Link(s): ADS8201
ADS8201
www.ti.com
SLAS534B – JULY 2009 – REVISED MAY 2010
A bridge sensor application is shown in Figure 32.
3V
10mF
1mF
3V
OPA358
240pF
1 mF
R2
+3V
VD
VA
REF
REFGND
AGND
PGAOUT
ADCIN
1kW
R3
Microprocessor
CONVST
DGND
PGAREF
ADS8201
2V - DV
IN0
SDO
2V + DV
IN1
SDI
G = 1/2/4/8
150W
(1)
R1
IN2
CS
(1)
RST
IN7
IN6
IN5
IN4
IN3
BUSY/INT
300W
SCLK
R1 creates proper common-mode voltage only for low-voltage operation.
Figure 32. Bridge Sensor Application
Submit Documentation Feedback
Copyright © 2009–2010, Texas Instruments Incorporated
Product Folder Link(s): ADS8201
27
ADS8201
SLAS534B – JULY 2009 – REVISED MAY 2010
www.ti.com
REVISION HISTORY
NOTE: Page numbers for previous revisions may differ from page numbers in the current version.
Changes from Revision A (November 2009) to Revision B
•
28
Page
Changed unit, and min and max values for Offset Error parameter in Electrical Characteristics table ............................... 3
Submit Documentation Feedback
Copyright © 2009–2010, Texas Instruments Incorporated
Product Folder Link(s): ADS8201
PACKAGE OPTION ADDENDUM
www.ti.com
7-Jun-2010
PACKAGING INFORMATION
Orderable Device
Status
(1)
Package Type Package
Drawing
Pins
Package Qty
ADS8201IBRGER
PREVIEW
VQFN
RGE
24
TBD
Call TI
Call TI
Samples Not Available
ADS8201IBRGET
PREVIEW
VQFN
RGE
24
TBD
Call TI
Call TI
Samples Not Available
ADS8201IRGER
ACTIVE
VQFN
RGE
24
3000
Green (RoHS
& no Sb/Br)
CU NIPDAU Level-2-260C-1 YEAR
Purchase Samples
ADS8201IRGET
ACTIVE
VQFN
RGE
24
250
Green (RoHS
& no Sb/Br)
CU NIPDAU Level-2-260C-1 YEAR
Request Free Samples
Eco Plan
(2)
Lead/
Ball Finish
MSL Peak Temp
(3)
Samples
(Requires Login)
(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 1
PACKAGE MATERIALS INFORMATION
www.ti.com
20-Jul-2010
TAPE AND REEL INFORMATION
*All dimensions are nominal
Device
Package Package Pins
Type Drawing
SPQ
Reel
Reel
A0
Diameter Width (mm)
(mm) W1 (mm)
B0
(mm)
K0
(mm)
P1
(mm)
W
Pin1
(mm) Quadrant
ADS8201IRGER
VQFN
RGE
24
3000
330.0
12.4
4.25
4.25
1.15
8.0
12.0
Q2
ADS8201IRGET
VQFN
RGE
24
250
180.0
12.4
4.25
4.25
1.15
8.0
12.0
Q2
Pack Materials-Page 1
PACKAGE MATERIALS INFORMATION
www.ti.com
20-Jul-2010
*All dimensions are nominal
Device
Package Type
Package Drawing
Pins
SPQ
Length (mm)
Width (mm)
Height (mm)
ADS8201IRGER
VQFN
RGE
24
3000
346.0
346.0
29.0
ADS8201IRGET
VQFN
RGE
24
250
190.5
212.7
31.8
Pack Materials-Page 2
IMPORTANT NOTICE
Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, modifications, enhancements, improvements,
and other changes to its products and services at any time and to discontinue any product or service without notice. Customers should
obtain the latest relevant information before placing orders and should verify that such information is current and complete. All products are
sold subject to TI’s terms and conditions of sale supplied at the time of order acknowledgment.
TI warrants performance of its hardware products to the specifications applicable at the time of sale in accordance with TI’s standard
warranty. Testing and other quality control techniques are used to the extent TI deems necessary to support this warranty. Except where
mandated by government requirements, testing of all parameters of each product is not necessarily performed.
TI assumes no liability for applications assistance or customer product design. Customers are responsible for their products and
applications using TI components. To minimize the risks associated with customer products and applications, customers should provide
adequate design and operating safeguards.
TI does not warrant or represent that any license, either express or implied, is granted under any TI patent right, copyright, mask work right,
or other TI intellectual property right relating to any combination, machine, or process in which TI products or services are used. Information
published by TI regarding third-party products or services does not constitute a license from TI to use such products or services or a
warranty or endorsement thereof. Use of such information may require a license from a third party under the patents or other intellectual
property of the third party, or a license from TI under the patents or other intellectual property of TI.
Reproduction of TI information in TI data books or data sheets is permissible only if reproduction is without alteration and is accompanied
by all associated warranties, conditions, limitations, and notices. Reproduction of this information with alteration is an unfair and deceptive
business practice. TI is not responsible or liable for such altered documentation. Information of third parties may be subject to additional
restrictions.
Resale of TI products or services with statements different from or beyond the parameters stated by TI for that product or service voids all
express and any implied warranties for the associated TI product or service and is an unfair and deceptive business practice. TI is not
responsible or liable for any such statements.
TI products are not authorized for use in safety-critical applications (such as life support) where a failure of the TI product would reasonably
be expected to cause severe personal injury or death, unless officers of the parties have executed an agreement specifically governing
such use. Buyers represent that they have all necessary expertise in the safety and regulatory ramifications of their applications, and
acknowledge and agree that they are solely responsible for all legal, regulatory and safety-related requirements concerning their products
and any use of TI products in such safety-critical applications, notwithstanding any applications-related information or support that may be
provided by TI. Further, Buyers must fully indemnify TI and its representatives against any damages arising out of the use of TI products in
such safety-critical applications.
TI products are neither designed nor intended for use in military/aerospace applications or environments unless the TI products are
specifically designated by TI as military-grade or "enhanced plastic." Only products designated by TI as military-grade meet military
specifications. Buyers acknowledge and agree that any such use of TI products which TI has not designated as military-grade is solely at
the Buyer's risk, and that they are solely responsible for compliance with all legal and regulatory requirements in connection with such use.
TI products are neither designed nor intended for use in automotive applications or environments unless the specific TI products are
designated by TI as compliant with ISO/TS 16949 requirements. Buyers acknowledge and agree that, if they use any non-designated
products in automotive applications, TI will not be responsible for any failure to meet such requirements.
Following are URLs where you can obtain information on other Texas Instruments products and application solutions:
Products
Applications
Amplifiers
amplifier.ti.com
Audio
www.ti.com/audio
Data Converters
dataconverter.ti.com
Automotive
www.ti.com/automotive
DLP® Products
www.dlp.com
Communications and
Telecom
www.ti.com/communications
DSP
dsp.ti.com
Computers and
Peripherals
www.ti.com/computers
Clocks and Timers
www.ti.com/clocks
Consumer Electronics
www.ti.com/consumer-apps
Interface
interface.ti.com
Energy
www.ti.com/energy
Logic
logic.ti.com
Industrial
www.ti.com/industrial
Power Mgmt
power.ti.com
Medical
www.ti.com/medical
Microcontrollers
microcontroller.ti.com
Security
www.ti.com/security
RFID
www.ti-rfid.com
Space, Avionics &
Defense
www.ti.com/space-avionics-defense
RF/IF and ZigBee® Solutions www.ti.com/lprf
Video and Imaging
www.ti.com/video
Wireless
www.ti.com/wireless-apps
Mailing Address: Texas Instruments, Post Office Box 655303, Dallas, Texas 75265
Copyright © 2010, Texas Instruments Incorporated