TEXAS INSTRUMENTS ADS1112 Technical data
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16-Bit Analog-to-Digital Converter with
Input Multiplexer and Onboard Reference
ADS1112
SBAS282D − JUNE 2003 − REVISED MARCH 2004
FEATURES
D COMPLETE DATA ACQUISITION SYSTEM IN
THE MSOP-10 AND LEADLESS QFN-STYLE
PACKAGES
D MEASUREMENTS FROM TWO DIFFERENTIAL
CHANNELS OR THREE SINGLE-ENDED
CHANNELS
2
D I
CINTERFACE—EIGHT ADDRESSES PIN-
SELECTABLE
D ONBOARD REFERENCE:
Accuracy: 2.048V ±0.05%
Drift: 5ppm/°C
D ONBOARD PGA
D ONBOARD OSCILLATOR
D 16 BITS, NO MISSING CODES
D INL: 0.01% of FSR max
D CONTINUOUS SELF-CALIBRATION
D SINGLE-CYCLE CONVERSION
D PROGRAMMABLE DATA RATE: 15SPS to
240SPS
D POWER SUPPLY: 2.7V to 5.5V
D LOW CURRENT CONSUMPTION: 240µA
DESCRIPTION
The ADS1112 is a precision, continuously self-calibrating
Analog-to-Digital (A/D) converter with two dif ferential or three
single-ended channels and up to 16 bits of resolution in the
small MSOP-10 and leadless QFN-style (small-outline,
no-lead) packages. The onboard 2.048V reference provides
an input range of ±2.048V differentially. The ADS1112 uses
2
an I
C-compatible serial interface and has two address pins
that allow a user to select one of the eight I
addresses. The ADS1112 operates from a single power
supply ranging from 2.7V to 5.5V.
The ADS1 112 can p erform c onversions at r ates o f 15, 30, 6 0,
or 240 samples per second (SPS). The onboard
programmable g ain a m plifier (PGA), which of fers gains of up
to eight, allow s smaller signals to be measured with high
resolution. In single-conversion mode, the ADS1112
automatically powers down after a conversion, greatly
reducing current cons umpti on during idle periods.
The ADS1112 is designed for applications requiring
high-resolution measurement, where space and power
consumption are maj or considerations . Typical applications
include portable instrumentation, industrial process control,
and smart transmitters.
2
C Slave
APPLICATIONS
D PORTABLE INSTRUMENTATION
D INDUSTRIAL PROCESS CONTROL
D SMART TRANSMITTERS
D CONSUMER GOODS
D FACTORY AUTOMATION
D TEMPERATURE MEASUREMENT
semiconductor products and disclaimers thereto appears at the end of this data sheet.
All trademarks are the property of their respective owners.
! !
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Copyright 2003−2004, Texas Instruments Incorporated
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ADS1112
MSOP-10
DGS
−40°C to +85°C
BHU
ADS1112
SON-10
DRC
−40°C to +85°C
BHV
SBAS282D − JUNE 2003 − REVISED MARCH 2004
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ABSOLUTE MAXIMUM RATINGS
(1)
VDD to GND −0.3V to +6V
Input Current 100mA, Momentary
Input Current 10mA, Continuous
Analog Inputs, A0, A1, Voltage to GND −0.3V to VDD + 0.3V
SDA, SCL Voltage to GND −0.5V to 6V
Maximum Junction Temperature +150°C
Operating Temperature Range −40°C to +125°C
Storage Temperature Range −60°C to +150°C
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.
Lead Tem perature (soldering, 10s) +300°C
(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 relia b i l i t y.
PACKAGE/ORDERING INFORMATION
PRODUCT PACKAGE-LEAD
(1)
For the most current specification and package information, refer to our web site at www.ti.com.
PACKAGE
DESIGNATOR
(1)
SPECIFIED
TEMPERATURE
RANGE
°
°
°
°
PACKAGE
MARKING
This integrated circuit can be damaged by ESD.
Texas Instruments recommends that all
integrated circuits be handled with appropriate
ORDERING NUMBER
ADS1112IDGST Tape and Reel, 250
ADS1112IDGSR Tape and Reel, 2500
ADS1112IDRCT Tape and Reel, 250
ADS1112IDRCR Tape and Reel, 3000
TRANSPORT MEDIA,
QUANTITY
Top View
Top View
MSOP-10
SON-10
Terminal Functions
TERMINAL
NAME NO. DESCRIPTION
AIN0 1 Differential Channel 1; Positive Input
Single-ended Channel 1 Input
AIN1 2 Differential Channel 1; Negative Input
Single-ended Channel 2 Input
GND 3 Ground
AIN2 4 Differential Channel 2; Positive Input
Single-ended Channel 3 Input
AIN3 5 Differential Channel 2; Negative Input
Single-ended Common Input
VDD 6 Power Supply: 2.7V to 5.5V
SDA 7 Serial Data: Transmits and receives
data
SCL 8 Serial Clock Input: Clocks output
data on SDA
A0 9 I2C Slave Address Select
A1 10 I2C Slave Address Select
2
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Resolution and No Missing Codes
Data Rate
Offset Error
Offset Drift
Offset vs VDD
Common-Mode Rejection
Supply Current
Power Dissipation
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SBAS282D − JUNE 2003 − REVISED MARCH 2004
ELECTRICAL CHARACTERISTICS
All specifications at −40°C to +85°C, VDD = 5V, and all PGAs, unless otherwise noted.
ADS1112
PARAMETER CONDITIONS
ANALOG INPUT
Full-Scale Input Voltage (V
Analog Input Voltage V
Differential Input Impedance 2.8/PGA MΩ
Common-Mode Input Impedance PGA = 1 3.5 MΩ
SYSTEM PERFORMANCE
Resolution and No Missing Codes DR = 00 12 12 Bits
Data Rate DR = 00 180 240 308 SPS
Output Noise See Typical Characteristic Curves
Integral Nonlinearity DR = 11, PGA = 1, End Point Fit
Offset Error PGA = 1 1.2 8 mV
Offset Drift PGA = 1 1.2 µV/°C
Offset vs VDD PGA = 1 800 µV/V
Channel Offset Match Match between any two channels 30 µV
Gain Error
PGA Gain Error Match
Gain Error Drift
Gain vs VDD 80 ppm/V
Channel Gain Match Match between any two channels 0.01 %
Common-Mode Rejection At DC and PGA = 8 95 105 dB
DIGITAL INPUT/OUTPUT
Logic Level
V
V
V
Input Leakage
I
H
I
L
POWER-SUPPLY REQUIREMENTS
Power-Supply Voltage VDD 2.7 5.5 V
Supply Current Power-Down 0.05 2 µA
Power Dissipation VDD = 5.0V 1.2 1.75 mW
(1)
(2)
(3)
(3)
(3)
(3)
IH
IL
OL
99% of full-scale.
FSR = full-scale range = 2 × 2.048V/PGA = 4.096V/PGA.
Includes all errors from onboard PGA and reference.
) − (V
IN+
to GND or V
IN+
PGA = 2 3.5 MΩ
PGA = 4 1.8 MΩ
PGA = 8 0.9 MΩ
DR = 01 14 14 Bits
DR = 10 15 15 Bits
DR = 11 16 16 Bits
DR = 01 45 60 77 SPS
DR = 10 22 30 39 SPS
DR = 11 11 15 20 SPS
PGA = 2 0.7 4 mV
PGA = 4 0.5 2.5 mV
PGA = 8 0.4 1.5 mV
PGA = 2 0.6 µV/°C
PGA = 4 0.3 µV/°C
PGA = 8 0.3 µV/°C
PGA = 2 400 µV/V
PGA = 4 200 µV/V
PGA = 8 150 µV/V
Match between any two PGA gains 0.02 0.10 %
At DC and PGA = 1 100 dB
IOL = 3mA GND 0.4 V
VIH = 5.5V 10 µA
VIL = GND −10 µA
Active Mode 240 350 µA
VDD = 3.0V 0.675 mW
) ±2.048/PGA V
IN−
to GND GND − 0.2 VDD + 0.2 V
IN−
(1)
MIN TYP MAX
±0.004 ±0.010 % of FSR
0.05 0.40 %
5 40 ppm/°C
0.7 • VDD 6 V
GND − 0.5 0.3 • VDD V
UNIT
(2)
3
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SBAS282D − JUNE 2003 − REVISED MARCH 2004
TYPICAL CHARACTERISTICS
At TA = 25°C and VDD = 5V, unless otherwise noted.
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4
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TYPICAL CHARACTERISTICS (continued)
At TA = 25°C and VDD = 5V, unless otherwise noted.
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SBAS282D − JUNE 2003 − REVISED MARCH 2004
5
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SBAS282D − JUNE 2003 − REVISED MARCH 2004
TYPICAL CHARACTERISTICS (continued)
At TA = 25°C and VDD = 5V, unless otherwise noted.
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THEORY OF OPERATION
The ADS1112 is a 16-bit, self-calibrating, delta-sigma A/D
converter with an input multiplexer. Extremely easy to design with and configure, the ADS1 112 allows precise measurements to be obtained with a minimum of effort.
The ADS1112 consists of a delta-sigma A/D converter
core with adjustable gain, a 2.048V reference, a clock oscillator, and an I
scribed in detail in the sections that follow.
ANALOG-TO-DIGITAL CONVERTER
The ADS1112 A/D converter core consists of a differential
switched-capacitor delta-sigma modulator followed by a
digital filter. The modulator measures the voltage difference between the positive and negative analog inputs selected by the input multiplexer and compares it to a reference voltage, which, in the ADS1112, is 2.048V. The digital
filter receives a high-speed bitstream from the modulator
and outputs a code, which is a number proportional to the
input voltage.
MULTIPLEXER
The ADS1112 has an input multiplexer that provides for
two differential or three single-ended input channels. Two
bits in the configuration register control the multiplexer
setting.
VOLTAGE REFERENCE
The ADS1112 contains an onboard 2.048V voltage reference. This reference is always used as the ADC voltage
reference; an external reference cannot be connected.
The ADS1112 voltage reference is internal only, and cannot be measured directly or used by external circuitry.
2
C interface. Each of these blocks are de-
The onboard reference specifications are part of the overall gain and drift specifications of the ADS1112. The converter drift and gain error specifications reflect the performance of the onboard reference as well as the
performance of the A/D converter core. There are no separate specifications for the onboard reference itself.
OUTPUT CODE CALCULATION
The output code is a scaled value that is proportional, except for clipping, to the voltage difference between the t wo
analog inputs. The output code is confined to a finite range
of numbers; this range depends on the number of bits
needed to represent the code. The number of bits needed
to represent the output code for the ADS1 112 depends on
the data rate, as shown in Table 1.
NUMBER OF
DATA RATE
15SPS 16 −32,768 32,767
30SPS 15 −16,384 16,383
60SPS 14 −8192 8191
240SPS 12 −2048 2047
BITS
Table 1. Minimum and Maximum Codes
For a minimum output code of Min Code, gain setting of the
PGA, and positive and negative input voltages of V
, the output code is given by the expression:
V
IN−
Output Code + −1 Min Code PGA
In the previous expression, it is important to note that the
negated minimum output code is used. The ADS1112
outputs codes in binary two’s complement format, so the
MINIMUM
CODE
(V
IN)
2.048V
MAXIMUM
) * (V
CODE
IN+
IN*
and
)
6
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