BB ADS7830

ADS7830
ADS
7830
®
SBAS302 – DECEMBER 2003
8-Bit, 8-Channel Sampling
ANALOG-TO-DIGITAL CONVERTER
with I2C™ Interface
FEATURES
APPLICATIONS
●
●
●
●
●
●
●
●
●
●
●
●
70kHz SAMPLING RATE
±0.5LSB INL/DNL
8 BITS NO MISSING CODES
4 DIFFERENTIAL/8 SINGLE-ENDED INPUTS
2.7V TO 5V OPERATION
BUILT-IN 2.5V REFERENCE/BUFFER
SUPPORTS ALL THREE I2C MODES:
Standard, Fast, and High-Speed
● LOW POWER:
180µW (Standard Mode)
300µW (High-Speed Mode)
675µW (Fast Mode)
● DIRECT PIN COMPATIBLE WITH ADS7828
● TSSOP-16 PACKAGE
VOLTAGE-SUPPLY MONITORING
ISOLATED DATA ACQUISITION
TRANSDUCER INTERFACE
BATTERY-OPERATED SYSTEMS
REMOTE DATA ACQUISITION
DESCRIPTION
The ADS7830 is a single-supply, low-power, 8-bit data
acquisition device that features a serial I2C interface and an
8-channel multiplexer. The Analog-to-Digital (A/D) converter
features a sample-and-hold amplifier and internal,
asynchronous clock. The combination of an I2C serial,
2-wire interface and micropower consumption makes the
ADS7830 ideal for applications requiring the A/D converter to
be close to the input source in remote locations and for
applications requiring isolation. The ADS7830 is available in
a TSSOP-16 package.
CH0
SAR
CH1
CH2
CH3
CH4
8-Channel
MUX
CH5
SDA
CH6
CH7
CDAC
Serial
Interface
COM
SCL
A0
Comparator
S/H Amp
A1
2.5V VREF
REFIN/REFOUT
Buffer
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.
All trademarks are the property of their respective owners.
Copyright © 2003, Texas Instruments Incorporated
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of Texas Instruments
standard warranty. Production processing does not necessarily include
testing of all parameters.
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ELECTROSTATIC
DISCHARGE SENSITIVITY
ABSOLUTE MAXIMUM RATINGS(1)
+VDD to GND ........................................................................ –0.3V to +6V
Digital Input Voltage to GND ................................. –0.3V to +VDD + 0.3V
Operating Temperature Range ...................................... –40°C to +105°C
Storage Temperature Range ......................................... –65°C to +150°C
Junction Temperature (TJ max) .................................................... +150°C
TSSOP Package
Power Dissipation .................................................... (TJ max – TA)/θJA
θJA Thermal Impedance ........................................................ 240°C/W
Lead Temperature, Soldering
Vapor Phase (60s) ............................................................ +215°C
Infrared (15s) ..................................................................... +220°C
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.
NOTE: (1) Stresses above those listed under “Absolute Maximum Ratings”
may cause permanent damage to the device. Exposure to absolute maximum
conditions for extended periods may affect device reliability.
PACKAGE/ORDERING INFORMATION(1)
MAXIMUM
INTEGRAL
LINEARITY
ERROR (LSB)
ADS7830I
"
PRODUCT
PACKAGE-LEAD
PACKAGE
DESIGNATOR
SPECIFIED
TEMPERATURE
RANGE
±0.5
TSSOP-16
PW
–40°C to +85°C
ADS7830IPWT
Tape and Reel, 250
"
"
"
"
ADS7830IPWR
Tape and Reel, 2500
ORDERING
NUMBER
TRANSPORT
MEDIA, QUANTITY
NOTE: (1) For the most current package and ordering information, refer to our web site at www.ti.com.
PIN CONFIGURATION
PIN DESCRIPTIONS
Top View
TSSOP
CH0
1
16
+VDD
CH1
2
15
SDA
CH2
3
14
SCL
CH3
4
13
A1
CH4
5
12
A0
ADS7830
PIN
NAME
1
CH0
Analog Input Channel 0
DESCRIPTION
2
CH1
Analog Input Channel 1
3
CH2
Analog Input Channel 2
4
CH3
Analog Input Channel 3
5
CH4
Analog Input Channel 4
6
CH5
Analog Input Channel 5
7
CH6
Analog Input Channel 6
8
CH7
Analog Input Channel 7
9
GND
Analog Ground
10 REFIN / REFOUT Internal +2.5V Reference, External Reference Input
CH5
6
11
COM
11
COM
CH6
7
10
REFIN / REFOUT
12
A0
Slave Address Bit 0
13
A1
Slave Address Bit 1
14
SCL
Serial Clock
15
SDA
Serial Data
16
+VDD
Power Supply, 3.3V Nominal
CH7
8
9
GND
Common to Analog Input Channel
ADS7830
2
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SBAS302
ELECTRICAL CHARACTERISTICS: +2.7V
At TA = –40°C to +85°C, +VDD = +2.7V, VREF = +2.5V, SCL Clock Frequency = 3.4MHz (High-Speed Mode), unless otherwise noted.
ADS7830E
PARAMETER
ANALOG INPUT
Full-Scale Input Scan
Absolute Input Range
CONDITIONS
MIN
Positive Input - Negative Input
Positive Input
Negative Input
0
–0.2
–0.2
Capacitance
Leakage Current
VOLTAGE REFERENCE OUTPUT
Range
Internal Reference Drift
Output Impedance
Quiescent Current
VOLTAGE REFERENCE INPUT
Range
Resistance
Current Drain
DIGITAL INPUT/OUTPUT
Logic Family
Logic Levels: VIH
VIL
VOL
Input Leakage: IIH
IIL
Data Format
±0.1
±0.1
+0.5
±0.05
±0.1
±0.05
100
72
Power Dissipation
Power-Down Mode
w/Wrong Address Selected
Full Power-Down
VREF
+VDD + 0.2
+0.2
V
V
V
pF
µA
VIN =
VIN =
VIN =
VIN =
2.5VPP
2.5VPP
2.5VPP
2.5VPP
at
at
at
at
±0.5
±0.5
+1
±0.25
±0.5
±0.25
5
–72
50
49
68
90
dB (3)
dB
dB
dB
dB
70
10
2.5
1kHz
1kHz
1kHz
1kHz
2.475
Internal Reference ON
Internal Reference OFF
Internal Reference ON, SCL and SDA pulled HIGH
2.5
15
110
1
850
0.05
2.525
V
ppm/°C
Ω
GΩ
µA
VDD
V
GΩ
µA
+VDD + 0.5
+VDD • 0.3
0.4
10
V
V
V
µA
µA
1
20
High-Speed Mode: SCL= 3.4MHz
Bits
LSB (1)
LSB
LSB
LSB
LSB
LSB
µVRMS
dB
kSPS(2)
kSPS
kSPS
µs
High-Speed Mode: SCL = 3.4MHz
Fast Mode: SCL = 400kHz
Standard Mode, SCL = 100kHz
CMOS
+VDD • 0.7
–0.3
Minimum 3mA Sink Current
VIH = +VDD +0.5
VIL = -0.3
-10
Straight
Binary
ADS7830 HARDWARE ADDRESS
POWER-SUPPLY REQUIREMENTS
Power-Supply Voltage, +VDD
Quiescent Current
UNITS
8
Conversion Time
AC ACCURACY
Total Harmonic Distortion
Signal-to-Ratio
Signal-to-(Noise+Distortion) Ratio
Spurious-Free Dynamic Range
Isolation Channel-to-Channel
MAX
25
±1
SYSTEM PERFORMANCE
No Missing Codes
Integral Linearity Error
Differential Linearity Error
Offset Error
Offset Error Match
Gain Error
Gain Error Match
Noise
Power-Supply Rejection
SAMPLING DYNAMICS
Throughput Frequency
TYP
10010
Specified Performance
High-Speed Mode: SCL = 3.4MHz
Fast Mode: SCL = 400kHz
Standard Mode, SCL = 100kHz
High-Speed Mode: SCL = 3.4MHz
Fast Mode: SCL = 400kHz
Standard Mode, SCL = 100kHz
High-Speed Mode: SCL = 3.4MHz
Fast Mode: SCL = 400kHz
Standard Mode, SCL = 100kHz
SCL Pulled HIGH, SDA Pulled HIGH
TEMPERATURE RANGE
Specified Performance
2.7
225
100
60
675
300
180
70
25
6
400
–40
Binary
3.6
320
3000
V
µA
µA
µA
µW
µW
µW
µA
µA
µA
nA
85
°C
1000
NOTES: (1) LSB means least significant bit. When VREF = 2.5V, 1LSB is 9.8mV. (2) kSPS means kilo samples-per-second. (3) THD measured out to the 9th-harmonic.
ADS7830
SBAS302
3
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ELECTRICAL CHARACTERISTICS: +5V
At TA = –40°C to +85°C, +VDD = +5.0V, VREF = External +5.0V, SCL Clock Frequency = 3.4MHz (High-Speed Mode), unless otherwise noted.
ADS7830E
PARAMETER
CONDITIONS
MIN
Positive Input - Negative Input
Positive Input
Negative Input
0
–0.2
–0.2
TYP
MAX
UNITS
VREF
+VDD + 0.2
+0.2
V
V
V
pF
µA
ANALOG INPUT
Full-Scale Input Scan
Absolute Input Range
Capacitance
Leakage Current
25
±1
SYSTEM PERFORMANCE
No Missing Codes
Integral Linearity Error
Differential Linearity Error
Offset Error
Offset Error Match
Gain Error
Gain Error Match
Noise
Power-Supply Rejection
SAMPLING DYNAMICS
Throughput Frequency
8
±0.1
±0.1
+0.5
±0.05
±0.1
±0.05
100
72
VOLTAGE REFERENCE OUTPUT
Range
Internal Reference Drift
Output Impedance
Quiescent Current
VOLTAGE REFERENCE INPUT
Range
Resistance
Current Drain
DIGITAL INPUT/OUTPUT
Logic Family
Logic Levels: VIH
VIL
VOL
Input Leakage: IIH
IIL
Data Format
Power Dissipation
Power-Down Mode
w/Wrong Address Selected
Full Power-Down
–72
50
49
68
90
dB (3)
dB
dB
dB
dB
70
10
2.5
VIN =
VIN =
VIN =
VIN =
5VPP
5VPP
5VPP
5VPP
at
at
at
at
1kHz
1kHz
1kHz
1kHz
2.475
Internal Reference ON
Internal Reference OFF
Int. Ref. ON, SCL and SDA pulled HIGH
2.5
15
110
1
1300
0.05
2.525
V
ppm/°C
Ω
GΩ
µA
VDD
V
GΩ
µA
+VDD + 0.5
+VDD • 0.3
0.4
10
V
V
V
µA
µA
1
20
High-Speed Mode: SCL = 3.4MHz
CMOS
+VDD • 0.7
–0.3
Minimum 3mA Sink Current
VIH = +VDD +0.5
VIL = -0.3
-10
Straight
Binary
ADS7830 HARDWARE ADDRESS
POWER-SUPPLY REQUIREMENTS
Power-Supply Voltage, +VDD
Quiescent Current
5
kSPS(2)
kSPS
kSPS
µs
High-Speed Mode: SCL = 3.4MHz
Fast Mode: SCL = 400kHz
Standard Mode, SCL = 100kHz
Conversion Time
AC ACCURACY
Total Harmonic Distortion
Signal-to-Ratio
Signal-to-(Noise+Distortion) Ratio
Spurious-Free Dynamic Range
Isolation Channel-to-Channel
Bits
LSB (1)
LSB
LSB
LSB
LSB
LSB
µVRMS
dB
±0.5
±0.5
+1
±0.25
±0.5
±0.25
10010
Specified Performance
High-Speed Mode: SCL = 3.4MHz
Fast Mode: SCL = 400kHz
Standard Mode, SCL = 100kHz
High-Speed Mode: SCL = 3.4MHz
Fast Mode: SCL = 400kHz
Standard Mode, SCL = 100kHz
High-Speed Mode: SCL = 3.4MHz
Fast Mode: SCL = 400kHz
Standard Mode, SCL = 100kHz
SCL Pulled HIGH, SDA Pulled HIGH
TEMPERATURE RANGE
Specified Performance
4.75
–40
5
750
300
150
3.75
1.5
0.75
400
150
35
400
Binary
5.25
1000
3000
V
µA
µA
µA
mW
mW
mW
µA
µA
µA
nA
85
°C
5
NOTES: (1) LSB means Least Significant Bit. When VREF = 5.0V, 1LSB is 19.5mV. (2) kSPS means kilo samples-per-second. (3) THD measured out to the 9th-harmonic.
ADS7830
4
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SBAS302
TIMING DIAGRAM
SDA
tBUF
tLOW
tF
tR
tHD; STA
tSP
SCL
tHD; STA
tSU; STA
tHD; DAT
STOP
tHIGH
tSU; STO
tSU; DAT
START
REPEATED
START
TIMING CHARACTERISTICS(1)
At TA = –40°C to +85°C, +VDD = +2.7V, unless otherwise noted.
PARAMETER
SYMBOL
CONDITIONS
SCL Clock Frequency
fSCL
Standard Mode
Fast Mode
High-Speed Mode, CB = 100pF max
High-Speed Mode, CB = 400pF max
Bus Free Time Between a STOP and
START Condition
tBUF
Standard Mode
Fast Mode
4.7
1.3
µs
µs
Hold Time (Repeated) START
Condition
tHD;STA
Standard Mode
Fast Mode
High-Speed Mode
4.0
600
160
µs
ns
ns
LOW Period of the SCL Clock
tLOW
Standard Mode
Fast Mode
High-Speed Mode, CB = 100pF max(2)
High-Speed Mode, CB = 400pF max(2)
4.7
1.3
160
320
µs
µs
ns
ns
HIGH Period of the SCL Clock
tHIGH
Standard Mode
Fast Mode
High-Speed Mode, CB = 100pF max(2)
High-Speed Mode, CB = 400pF max(2)
4.0
600
60
120
µs
ns
ns
ns
Setup Time for a Repeated START
Condition
tSU;STA
Standard Mode
Fast Mode
High-Speed Mode
4.7
600
160
µs
ns
ns
Data Setup Time
tSU;DAT
Standard Mode
Fast Mode
High-Speed Mode
250
100
10
ns
ns
ns
Data Hold Time
tHD;DAT
Standard Mode
Fast Mode
High-Speed Mode, CB = 100pF max(2)
High-Speed Mode, CB = 400pF max(2)
0
0
0(3)
0(3)
3.45
0.9
70
150
µs
µs
ns
ns
tRCL
Standard Mode
Fast Mode
High-Speed Mode, CB = 100pF max(2)
High-Speed Mode, CB = 400pF max(2)
20 + 0.1CB
10
20
1000
300
40
80
ns
ns
ns
ns
Standard Mode
Fast Mode
High-Speed Mode, CB = 100pF max(2)
High-Speed Mode, CB = 400pF max(2)
20 + 0.1CB
10
20
1000
300
80
160
ns
ns
ns
ns
Standard Mode
Fast Mode
High-Speed Mode, CB = 100pF max(2)
High-Speed Mode, CB = 400pF max(2)
20 + 0.1CB
10
20
300
300
40
80
ns
ns
ns
ns
Rise Time of SCL Signal
Rise Time of SCL Signal After a
Repeated START Condition and
After an Acknowledge Bit
tRCL1
Fall Time of SCL Signal
tFCL
ADS7830
SBAS302
MIN
MAX
UNITS
100
400
3.4
1.7
kHz
kHz
MHz
MHz
5
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TIMING CHARACTERISTICS(1) (Cont.)
At TA = –40°C to +85°C, +VDD = +2.7V, unless otherwise noted.
PARAMETER
Rise Time of SDA Signal
Fall Time of SDA Signal
Setup Time for STOP Condition
SYMBOL
CONDITIONS
MIN
MAX
UNITS
tRDA
Standard Mode
Fast Mode
High-Speed Mode, CB = 100pF max(2)
High-Speed Mode, CB = 400pF max(2)
20 + 0.1CB
10
20
1000
300
80
160
ns
ns
ns
ns
Standard Mode
Fast Mode
High-Speed Mode, CB = 100pF max(2)
High-Speed Mode, CB = 400pF max(2)
20 + 0.1CB
10
20
300
300
80
160
ns
ns
ns
ns
Standard Mode
Fast Mode
High-Speed Mode
4.0
600
160
tFDA
tSU;STO
µs
ns
ns
Capacitive Load for SDA and SCL Line
CB
Pulse Width of Spike Suppressed
tSP
Noise Margin at the HIGH Level for
Each Connected Device (Including
Hysteresis)
VNH
Standard Mode
Fast Mode
High-Speed Mode
0.2VDD
V
Noise Margin at the LOW Level for
Each Connected Device (Including
Hysteresis)
VNL
Standard Mode
Fast Mode
High-Speed Mode
0.1VDD
V
Fast Mode
High-Speed Mode
400
pF
50
10
ns
ns
NOTES: (1) All values referred to VIHMIN and VILMAX levels. (2) For bus line loads CB between 100pF and 400pF the timing parameters must be linearly interpolated.
(3) A device must internally provide a data hold time to bridge the undefined part between VIH and VIL of the falling edge of the SCLH signal. An input circuit with
a threshold as low as possible for the falling edge of the SCLH signal minimizes this hold time.
ADS7830
6
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SBAS302
TYPICAL CHARACTERISTICS
TA = +25°C, VDD = +2.7V, VREF = External +2.5V, fSAMPLE = 50kHz, unless otherwise noted.
INTEGRAL LINEARITY ERROR vs CODE
(2.5V Internal Reference)
FFT vs FREQUENCY
0.5
0
0.4
0.3
0.2
−40
ILE (LSB)
Amplitude (dB)
−20
−60
0.1
0
−0.1
−0.2
−0.3
−80
−0.4
−0.5
−100
0
10
20
25
0
64
128
Output Code
Frequency (kHz)
255
INTEGRAL LINEARITY ERROR vs CODE
(2.5V External Reference)
DIFFERENTIAL LINEARITY ERROR vs CODE
(2.5V Internal Reference)
0.5
0.5
0.4
0.4
0.3
0.3
0.2
0.2
ILE (LSB)
ILE (LSB)
192
0.1
0
−0.1
0.1
0
−0.1
−0.2
−0.2
−0.3
−0.3
−0.4
−0.4
−0.5
−0.5
0
64
128
Output Code
192
0
255
DIFFERENTIAL LINEARITY ERROR vs CODE
(2.5V External Reference)
64
128
Output Code
192
255
CHANGE IN OFFSET vs TEMPERATURE
0.10
0.5
0.4
Delta from 25°C (LSB)
0.3
ILE (LSB)
0.2
0.1
0
−0.1
−0.2
−0.3
0.05
0
−0.05
−0.4
−0.10
−0.5
0
64
128
Output Code
192
−50
255
0
25
50
75
100
Temperature (°C)
ADS7830
SBAS302
−25
7
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TYPICAL CHARACTERISTICS (Cont.)
TA = +25°C, VDD = +2.7V, VREF = External +2.5V, fSAMPLE = 50kHz, unless otherwise noted.
CHANGE IN GAIN vs TEMPERATURE
INTERNAL REFERENCE vs TEMPERATURE
0.10
2.51875
Internal Reference (V)
Delta from 25°C (LSB)
2.51250
0.05
0
−0.05
2.50625
2.50000
2.49375
2.48750
−0.10
2.48125
−50
−25
0
25
50
75
100
–50
–25
0
Temperature (°C)
POWER-DOWN SUPPLY CURRENT
vs TEMPERATURE
50
75
100
SUPPLY CURRENT vs TEMPERATURE
750
400
600
350
Supply Current (µA)
Supply Current (nA)
25
Temperature (°C)
450
300
150
0
300
250
200
150
–150
100
–50
–25
0
25
50
75
100
125
–50
–25
0
Temperature (°C)
25
50
75
100
Temperature (°C)
SUPPLY CURRENT vs I2C BUS RATE
300
Supply Current (µA)
250
200
150
100
50
0
10
100
I2C
1k
10k
Bus Rate (KHz)
ADS7830
8
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SBAS302
THEORY OF OPERATION
range for a 0V to +VDD analog input. This external reference
can be as low as 50mV.
The ADS7830 is a classic Successive Approximation Register (SAR) A/D converter. The architecture is based on capacitive redistribution which inherently includes a sampleand-hold function. The converter is fabricated on a 0.6µ
CMOS process.
As the reference voltage is reduced, the analog voltage
weight of each digital output code is reduced. This is often
referred to as the LSB (least significant bit) size and is equal
to the reference voltage divided by 256. This means that any
offset or gain error inherent in the A/D converter will appear
to increase, in terms of LSB size, as the reference voltage is
reduced.
The ADS7830 core is controlled by an internally generated
free-running clock. When the ADS7830 is not performing
conversions or being addressed, it keeps the A/D converter
core powered off, and the internal clock does not operate.
The noise inherent in the converter will also appear to increase
with lower LSB size. With a 2.5V reference, the internal noise
of the converter typically contributes only 0.02LSB peak-topeak of potential error to the output code. When the external
reference is 50mV, the potential error contribution from the
internal noise will be 50 times larger—1LSB. The errors due to
the internal noise are Gaussian in nature and can be reduced
by averaging consecutive conversion results.
The simplified diagram of input and output for the ADS7830
is shown in Figure 1.
ANALOG INPUT
When the converter enters the hold mode, the voltage on the
selected CHx pin is captured on the internal capacitor array.
The input current on the analog inputs depends on the
conversion rate of the device. During the sample period, the
source must charge the internal sampling capacitor (typically
25pF). After the capacitor has been fully charged, there is no
further input current. The amount of charge transfer from the
analog source to the converter is a function of conversion rate.
DIGITAL INTERFACE
The ADS7830 supports the I2C serial bus and data transmission protocol, in all three defined modes: standard, fast, and
high-speed. A device that sends data onto the bus is defined
as a transmitter, and a device receiving data as a receiver.
The device that controls the message is called a “master.”
The devices that are controlled by the master are “slaves.”
The bus must be controlled by a master device that generates the serial clock (SCL), controls the bus access, and
generates the START and STOP conditions. The ADS7830
operates as a slave on the I2C bus. Connections to the bus
are made via the open-drain I/O lines SDA and SCL.
REFERENCE
The ADS7830 can operate with its internal 2.5V reference or
an external reference. When using a +2.7V supply, the
internal 2.5V reference will provide full dynamic range for a
0V to +VDD analog input. If a +5V supply is used, an external
5V reference is required in order to provide full dynamic
+2.7V to +3.6V
5Ω
+ 1µF to
10µF
0.1µF
REFIN/
REFOUT
SDA
CH1
SCL
CH4
2kΩ
+ 1µF to
10µF
CH0
CH2 ADS7828
CH3
2kΩ
VDD
Microcontroller
A0
A1
GND
CH5
CH6
CH7
COM
FIGURE 1. Simplified I/O of the ADS7830.
ADS7830
SBAS302
9
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must be taken into account. A master must signal an end of
data to the slave by not generating an acknowledge bit on the
last byte that has been clocked out of the slave. In this case,
the slave must leave the data line HIGH to enable the master
to generate the STOP condition.
The following bus protocol has been defined (as shown in
Figure 2):
• Data transfer may be initiated only when the bus is not
busy.
• During data transfer, the data line must remain stable
whenever the clock line is HIGH. Changes in the data line
while the clock line is HIGH will be interpreted as control
signals.
Figure 2 details how data transfer is accomplished on the I2C
bus. Depending upon the state of the R/W bit, two types of
data transfer are possible:
1. Data transfer from a master transmitter to a slave
receiver. The first byte transmitted by the master is the
slave address. Next follows a number of data bytes. The
slave returns an acknowledge bit after the slave address
and each received byte.
Accordingly, the following bus conditions have been defined:
Bus Not Busy: Both data and clock lines remain HIGH.
Start Data Transfer: A change in the state of the data line,
from HIGH to LOW, while the clock is HIGH, defines a
START condition.
2. Data transfer from a slave transmitter to a master
receiver. The first byte, the slave address, is transmitted
by the master. The slave then returns an acknowledge bit.
Next, a number of data bytes are transmitted by the slave
to the master. The master returns an acknowledge bit
after all received bytes other than the last byte. At the end
of the last received byte, a not-acknowledge is returned.
Stop Data Transfer: A change in the state of the data line,
from LOW to HIGH, while the clock line is HIGH, defines the
STOP condition.
Data Valid: The state of the data line represents valid data,
when, after a START condition, the data line is stable for the
duration of the HIGH period of the clock signal. There is one
clock pulse per bit of data.
The master device generates all of the serial clock pulses
and the START and STOP conditions. A transfer is ended
with a STOP condition or a repeated START condition. Since
a repeated START condition is also the beginning of the next
serial transfer, the bus will not be released.
Each data transfer is initiated with a START condition and
terminated with a STOP condition. The number of data bytes
transferred between START and STOP conditions is not
limited and is determined by the master device. The information is transferred byte-wise and each receiver acknowledges with a ninth-bit.
The ADS7830 may operate in the following two modes:
• Slave Receiver Mode: Serial data and clock are received
through SDA and SCL. After each byte is received, an
acknowledge bit is transmitted. START and STOP conditions are recognized as the beginning and end of a serial
transfer. Address recognition is performed by hardware
after reception of the slave address and direction bit.
Within the I2C bus specifications a standard mode (100kHz
clock rate), a fast mode (400kHz clock rate), and a highspeed mode (3.4MHz clock rate) are defined. The ADS7830
works in all three modes.
Acknowledge: Each receiving device, when addressed, is
obliged to generate an acknowledge after the reception of
each byte. The master device must generate an extra clock
pulse that is associated with this acknowledge bit.
• Slave Transmitter Mode: The first byte (the slave address) is received and handled as in the slave receiver
mode. However, in this mode the direction bit will indicate
that the transfer direction is reversed. Serial data is transmitted on SDA by the ADS7830 while the serial clock is
input on SCL. START and STOP conditions are recognized as the beginning and end of a serial transfer.
A device that acknowledges must pull down the SDA line
during the acknowledge clock pulse in such a way that the
SDA line is stable LOW during the HIGH period of the
acknowledge clock pulse. Of course, setup and hold times
SDA
MSB
Slave Address
R/W
Direction
Bit
Acknowledgement
Signal from
Receiver
Acknowledgement
Signal from
Receiver
1
SCL
2
6
7
8
9
ACK
START
Condition
1
2
3-8
8
9
ACK
Repeated If More Bytes Are Transferred
STOP Condition
or Repeated
START Condition
FIGURE 2. Basic Operation of the ADS7830.
ADS7830
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SBAS302
Address Byte
Command Byte
MSB
6
5
4
3
2
1
LSB
MSB
6
5
4
3
2
1
LSB
1
0
0
1
0
A1
A0
R/W
SD
C2
C1
C0
PD1
PD0
X
X
The address byte is the first byte received following the
START condition from the master device. The first five bits
(MSBs) of the slave address are factory pre-set to 10010.
The next two bits of the address byte are the device select
bits, A1 and A0. Input pins (A1-A0) on the ADS7830 determine these two bits of the device address for a particular
ADS7830. A maximum of four devices with the same pre-set
code can therefore be connected on the same bus at one
time.
The ADS7830’s operating mode is determined by a command byte which is illustrated above.
The A1-A0 Address Inputs can be connected to VDD or digital
ground. The device address is set by the state of these pins
upon power-up of the ADS7830.
See Table I for Truth Table.
SD: Single-Ended/Differential Inputs
0: Differential Inputs
1: Single-Ended Inputs
C2 - C0: Channel Selections
PD1 - 0: Power-Down Selection
X: Unused
POWER-DOWN SELECTION
The last bit of the address byte (R/W) defines the operation
to be performed. When set to a “1” a read operation is
selected; when set to a “0” a write operation is selected.
Following the START condition the ADS7830 monitors the
SDA bus, checking the device type identifier being transmitted. Upon receiving the 10010 code, the appropriate device
select bits, and the R/W bit, the slave device outputs an
acknowledge signal on the SDA line.
PD1
PD0
0
0
Power Down Between A/D Converter Conversions
DESCRIPTION
0
1
Internal Reference OFF and A/D Converter ON
1
0
Internal Reference ON and A/D Converter OFF
1
1
Internal Reference ON and A/D Converter ON
INITIATING CONVERSION
Provided the master has write-addressed it, the ADS7830
turns on the A/D converter’s section and begins conversions
when it receives BIT 4 of the command byte shown in the
Command Byte. If the command byte is correct, the ADS7830
will return an ACK condition.
CHANNEL SELECTION CONTROL
SD
C2
C1
C0
CH0
CH1
0
0
0
0
+IN
–IN
0
0
0
1
—
—
0
0
1
0
—
—
0
0
1
1
—
0
1
0
0
–IN
CH2
CH3
CH4
CH5
CH6
CH7
COM
—
—
—
—
—
—
—
+IN
–IN
—
—
—
—
—
—
—
+IN
–IN
—
—
—
—
—
—
—
—
+IN
–IN
—
+IN
—
—
—
—
—
—
—
0
1
0
1
—
—
–IN
+IN
—
—
—
—
—
0
1
1
0
—
—
—
—
–IN
+IN
—
—
—
0
1
1
1
—
—
—
—
—
—
–IN
+IN
—
1
0
0
0
+IN
—
—
—
—
—
—
—
–IN
1
0
0
1
—
—
+IN
—
—
—
—
—
–IN
1
0
1
0
—
—
—
—
+IN
—
—
—
–IN
1
0
1
1
—
—
—
—
—
—
+IN
—
–IN
1
1
0
0
—
+IN
—
—
—
—
—
—
–IN
1
1
0
1
—
—
—
+IN
—
—
—
—
–IN
1
1
1
0
—
—
—
—
—
+IN
—
—
–IN
1
1
1
1
—
—
—
—
—
—
—
+IN
–IN
TABLE I. Channel Selection Control Addressed by Command BYTE.
ADS7830
SBAS302
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READING DATA
modes. It may be desirable to remain in HS mode after
reading a conversion; to do this, issue a repeated START
instead of a STOP at the end of the read sequence, since a
STOP causes the part to return to F/S mode.
Data can be read from the ADS7830 by read-addressing the
part (LSB of address byte set to 1) and receiving the
transmitted byte. Converted data can only be read from the
ADS7830 once a conversion has been initiated as described
in the preceding section.
LAYOUT
For optimum performance, care should be taken with the
physical layout of the ADS7830 circuitry. The basic SAR
architecture is sensitive to glitches or sudden changes on the
power supply, reference, ground connections, and digital
inputs that occur just prior to latching the output of the analog
comparator. Therefore, during any single conversion for an
“n-bit” SAR converter, there are n “windows” in which large
external transient voltages can easily affect the conversion
result. Such glitches might originate from switching power
supplies, nearby digital logic, and high-power devices.
Each 8-bit data word is returned in one byte, as shown
below, where D7 is the MSB of the data word, and D0 is the
LSB.
DATA
MSB
6
5
4
3
2
1
LSB
D7
D6
D5
D4
D3
D2
D1
D0
READING IN F/S MODE
With this in mind, power to the ADS7830 should be clean and
well-bypassed. A 0.1µF ceramic bypass capacitor should be
placed as close to the device as possible. A 1µF to 10µF
capacitor may also be needed if the impedance of the
connection between +VDD and the power supply is high.
Figure 3 describes the interaction between the master and
the slave ADS7830 in Fast or Standard (F/S) mode. At the
end of reading conversion data the ADS7830 can be issued
a repeated START condition by the master to secure bus
operation for subsequent conversions of the A/D converter.
This would be the most efficient way to perform continuous
conversions.
The ADS7830 architecture offers no inherent rejection of
noise or voltage variation in regards to using an external
reference input. This is of particular concern when the
reference input is tied to the power supply. Any noise and
ripple from the supply will appear directly in the digital results.
While high-frequency noise can be filtered out, voltage variation due to line frequency (50Hz or 60Hz) can be difficult to
remove.
READING IN HS MODE
High Speed (HS) mode is fast enough that codes can be
read out one at a time. In HS mode, there is not enough time
for a single conversion to complete between the reception of
a repeated START condition and the read-addressing byte,
so the ADS7830 stretches the clock after the read-addressing byte has been fully received, holding it LOW until the
conversion is complete.
The GND pin should be connected to a clean ground point.
In many cases, this will be the “analog” ground. Avoid
connections that are too near the grounding point of a
microcontroller or digital signal processor. The ideal layout
will include an analog ground plane dedicated to the converter and associated analog circuitry.
See Figure 4 for a typical read sequence for HS mode.
Included in the read sequence is the shift from F/S to HS
ADC Sampling Mode
ADC Power-Down Mode
S
1
0
0
1
0
A1
A0
W
A
SD C2
0
0
1
0
A1
X
A
ADC Power-Down Mode
(depending on power-down selection bits)
ADC Converting Mode
1
C0 PD1 PD0 X
Command Byte
Write-Addressing Byte
Sr
C1
A0
R
A
D7
D6
D5 D4
D3
D2
D1
D0
N
P
See Note (1)
Read-Addressing Byte
From Master to Slave
From Slave to Master
1 x (8 Bits + not-ack)
A = acknowledge (SDA LOW)
N = not acknowledge (SDA HIGH)
S = START Condition
P = STOP Condition
Sr = repeated START condition
W = '0' (WRITE)
R = '1' (READ)
NOTE: (1) To secure bus operation and loop back to the stage of write-addressing for next conversion, use repeated START.
FIGURE 3. Typical Read Sequence in F/S Mode.
ADS7830
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SBAS302
F/S Mode
S
0
0
0
0
1
X
X
X
N
HS Mode Master Code
HS Mode Enabled
ADC Power-Down Mode
Sr
1
0
0
1
0
A1
A0
W
A
Write-Addressing Byte
ADC Sampling Mode
SD
C2 C1
C0 PD1 PD0 X
X
A
Command Byte
HS Mode Enabled
ADC Converting Mode
Sr
1
0
0
1
0
A1
A0
R
A
SCLH(2) is stretched LOW waiting for data conversion
Read-Addressing Byte
Return to F/S Mode(1)
HS Mode Enabled
ADC Power-Down Mode
(depending on power-down selection bits)
D7
D6
D5
D4
D3
D2
D1
D0
N
P
1 x (8 Bits + not-ack)
From Master to Slave
From Slave to Master
A = acknowledge (SDA LOW)
N = not acknowledge (SDA HIGH)
S = START Condition
P = STOP Condition
Sr = repeated START condition
W = '0' (WRITE)
R = '1' (READ)
NOTES: (1) To remain in HS mode, use repeated START instead of STOP.
(2) SCLH is SCL in HS mode.
FIGURE 4. Typical Read Sequence in HS Mode.
ADS7830
SBAS302
13
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PACKAGE OPTION ADDENDUM
www.ti.com
31-Dec-2003
PACKAGING INFORMATION
ORDERABLE DEVICE
STATUS(1)
PACKAGE TYPE
PACKAGE DRAWING
PINS
PACKAGE QTY
ADS7830IPWR
ACTIVE
TSSOP
PW
16
2500
ADS7830IPWT
ACTIVE
TSSOP
PW
16
250
(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.
MECHANICAL DATA
MTSS001C – JANUARY 1995 – REVISED FEBRUARY 1999
PW (R-PDSO-G**)
PLASTIC SMALL-OUTLINE PACKAGE
14 PINS SHOWN
0,30
0,19
0,65
14
0,10 M
8
0,15 NOM
4,50
4,30
6,60
6,20
Gage Plane
0,25
1
7
0°– 8°
A
0,75
0,50
Seating Plane
0,15
0,05
1,20 MAX
PINS **
0,10
8
14
16
20
24
28
A MAX
3,10
5,10
5,10
6,60
7,90
9,80
A MIN
2,90
4,90
4,90
6,40
7,70
9,60
DIM
4040064/F 01/97
NOTES: A.
B.
C.
D.
All linear dimensions are in millimeters.
This drawing is subject to change without notice.
Body dimensions do not include mold flash or protrusion not to exceed 0,15.
Falls within JEDEC MO-153
POST OFFICE BOX 655303
• DALLAS, TEXAS 75265
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