AD
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AD
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ADS1225
ADS1226
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22
6
www.ti.com ....................................................................................................................................................... SBAS346C – MAY 2006 – REVISED JANUARY 2009
24-Bit Analog-to-Digital Converter
with One- and Two-Channel Differential Inputs and Internal Oscillator
FEATURES
DESCRIPTION
1
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100SPS Data Rate (High-Speed Mode)
Single-Cycle Settling
Easy Conversion Control with START Pin
Automatic Shutdown
Low Noise: 4µVRMS Noise (High-Resolution
Mode)
Input Multiplexer with Two Differential
Channels (ADS1226)
Voltage Reference Supports Ratiometric
Measurements
Self-Calibrating
Simple Read-Only 2-Wire Serial Interface
Internal High-Impedance Input Buffer
Internal Temperature Sensor
Internal Oscillator
Low-Power: 1mW While Operating, < 1µA
During Shutdown
Analog and Digital Supplies: 2.7V to 5.5V
APPLICATIONS
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Hand-Held Instrumentation
Portable Medical Equipment
Industrial Process Control
The ADS1225 and ADS1226 are 24-bit delta-sigma
analog-to-digital (A/D) converters. They offer
excellent performance, ease-of-use, and low power in
a small 4mm × 4mm QFN package and are
well-suited
for
demanding
high-resolution
measurements, especially in portable and other
space-saving and power-constrained applications.
The ADS1225 and ADS1226 convert on command
using a dedicated START pin. Simply pulse this pin to
initiate a conversion. Data is read in a single cycle for
retrieval over a 2-wire serial interface that easily
connects to popular microcontrollers like the
MSP430. After the conversion completes, the
ADS1225 and ADS1226 automatically shuts down all
circuitry.
Internal features include a two-channel multiplexer
(ADS1226), selectable input buffer, temperature
sensor, and oscillator. The full-scale range is defined
by the external voltage reference with support
provided for up to a 5V differential input signal. Two
operating modes allow for speed (100SPS data rate,
15µVRMS noise) or resolution (4µVRMS noise, 16SPS
data rate).
The ADS1225/6 supports 2.7 to 5.5V analog and
digital supplies. Power consumption is 1mW while
converting with 3V supplies. The ADS1225 and
ADS1226 are fully specified over an extended
industrial temperature range of –40°C to +105°C.
TEMPEN
AVDD
VREFP VREFN
DVDD
START
AINP1
AINN1
MUX
Buffer
AINP2
DS
ADC
Serial Interface
SCLK
DRDY/DOUT
AINN2
Oscillator
MUX
BUFEN
MODE
GND
ADS1226 Only
1
2
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.
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 © 2006–2009, Texas Instruments Incorporated
ADS1225
ADS1226
SBAS346C – MAY 2006 – REVISED JANUARY 2009 ....................................................................................................................................................... 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.
ORDERING INFORMATION
For the most current package and ordering information, see the Package Option Addendum located at the end of
this data sheet or see the TI web site at www.ti.com.
ABSOLUTE MAXIMUM RATINGS (1)
Over operating free-air temperature range, unless otherwise noted.
ADS1225, ADS1226
UNIT
–0.3 to +6
V
AVDD to GND
DVDD to GND
–0.3 to +6
V
100, momentary
mA
10, continuous
mA
Analog input voltage to GND
–0.3 to AVDD +0.3
V
Digital input voltage to GND
–0.3 to AVDD +0.3
V
+150
°C
Operating temperature range
–55 to +125
°C
Storage temperature range
–50 to +150
°C
Input current
Maximum junction temperature
(1)
2
Stresses above these ratings may cause permanent damage. Exposure to absolute maximum conditions for extended periods may
degrade device reliability. These are stress ratings only, and functional operation of the device at these or any other conditions beyond
those specified is not implied.
Submit Documentation Feedback
Copyright © 2006–2009, Texas Instruments Incorporated
Product Folder Link(s): ADS1225 ADS1226
ADS1225
ADS1226
www.ti.com ....................................................................................................................................................... SBAS346C – MAY 2006 – REVISED JANUARY 2009
ELECTRICAL CHARACTERISTICS
All specifications at TA = –40°C to +105°C, AVDD = +5V, DVDD = +3V, and VREF = +5V, unless otherwise noted.
ADS1225, ADS1226
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
Analog Input
Full-scale input voltage
Absolute input voltage
Differential input impedance
Common-mode input impedance
AINP – AINN
±VREF
V
Buffer off; AINP, AINN with respect to GND
GND – 0.1
AVDD + 0.1
Buffer on; AINP, AINN with respect to GND
GND + 0.05
AVDD – 1.5
V
V
Buffer off
2
MΩ
Buffer on
1
GΩ
Buffer off
4
MΩ
System Performance
Resolution
Data rate
Integral nonlinearity (INL)
24
Bits
High-Speed mode
75
100
125
SPS (1)
High-Resolution mode
12
16
22
SPS (1)
% of FSR (2)
0.0005
0.0020
Offset error
End-point fit
60
200
Offset error drift
0.3
Gain error
0.004
Gain error drift
0.025
%
0.3
ppm/°C
95
dB
dB
Common-mode rejection
At dc
Analog power-supply rejection
At dc, ± 10% Δ in AVDD
95
Digital power-supply rejection
At dc, DVDD = 2.7V to 5.5V
80
dB
High-Speed mode
1.5
ppm of FSR, rms
High-Resolution mode
0.4
ppm of FSR, rms
TA = +25°C
106
mV
360
µV/°C
Noise
85
µV
µV/°C
Temperature Sensor
Temperature sensor voltage
Temperature sensor coefficient
Voltage Reference Input
Reference input voltage
0.5
AVDD
V
Negative reference input
VREF = VREFP – VREFN
GND – 0.1
VREFP – 0.5
V
Positive reference input
VREFN + 0.5
AVDD + 0.1
Voltage reference impedance
(1)
(2)
1.5
V
MΩ
SPS = samples per second.
FSR = full-scale range = 2 × VREF.
Copyright © 2006–2009, Texas Instruments Incorporated
Product Folder Link(s): ADS1225 ADS1226
Submit Documentation Feedback
3
ADS1225
ADS1226
SBAS346C – MAY 2006 – REVISED JANUARY 2009 ....................................................................................................................................................... www.ti.com
ELECTRICAL CHARACTERISTICS (continued)
All specifications at TA = –40°C to +105°C, AVDD = +5V, DVDD = +3V, and VREF = +5V, unless otherwise noted.
ADS1225, ADS1226
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
Digital Input/Output
Logic
levels
VIH
0.8 DVDD
DVDD + 0.1
V
VIL
GND – 0.1
0.2 DVDD
V
VOH
IOH = 1mA
VOL
IOL = 1mA
0.8 DVDD
V
Input leakage
0.2 DVDD
V
±10
µA
V
Power Supply
AVDD
2.7
5.5
DVDD
2.7
5.5
AVDD current
DVDD current
Total power dissipation
V
Shutdown
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