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SBAS286C − JUNE 2003 − REVISED JANUARY 2009
FEATURES
D 240SPS Data Rate with 4MHz Clock
D 20-Bit Effective Resolution
D Input Multiplexer with Four Differential
D
D
D
D
D
D
D
D
D
D
Channels
Pin-Selectable, High-Impedance Input Buffer
±5V Differential Input Range
0.0003% INL (typ), 0.0015% INL (max)
Self-Calibrating
Simple 2-Wire Serial Interface
On-Chip Temperature Sensor
Single Conversions with Standby Mode
Low Current Consumption: 300µA
Analog Supply: 2.7V to 5.5V
Digital Supply: 2.7V to 5.5V
APPLICATIONS
D Hand-Held Instrumentation
D Portable Medical Equipment
D Industrial Process Control
D Weigh Scales
DESCRIPTION
The ADS1224 is a 4-channel, 24-bit, delta-sigma analog-to-digital (A/D) converter. It offers excellent performance and low power in a TSSOP-20 package. The
ADS1224 is well-suited for demanding, high-resolution
measurements, especially in portable systems and other space-saving and power-constrained applications.
A delta-sigma (∆Σ) modulator and digital filter form the
basis of the A/D converter. The analog modulator has
a ±5V differential input range. An input multiplexer
(MUX) is used to select between four separate
differential input channels. A buffer can be selected to
increase the input impedance of the measurement.
A simple, 2-wire serial interface provides all the
necessary control. Data retrieval, self-calibration, and
Standby mode are handled with a few simple
waveforms. When only single conversions are needed,
the ADS1224 can be quickly shut down (Standby mode)
while idle between measurements to dramatically
reduce the overall power consumption. Multiple
ADS1224s can be connected together to create a
synchronously sampling multichannel measurement
system. The ADS1224 is designed to easily connect to
microcontrollers, such as the MSP430.
The ADS1224 supports 2.7V to 5.5V analog supplies
and 2.7V to 5.5V digital supplies. Power is typically less
than 1mW in 3V operation and less than 1µW during
Standby mode.
TEMPEN
AVDD
VREFP VREFN
DVDD
CLK
AINP1
AINN1
AINP2
AINN2
Mux
Buffer
AINP3
AINN3
∆Σ
Modulator
Digital Filter
and
Serial Interface
SCLK
DRDY/DOUT
AINP4
AINN4
MUX0
MUX1
BUFEN
GND
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 2003−2008, Texas Instruments Incorporated
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SBAS286C − JUNE 2003 − REVISED JANUARY 2009
ORDERING INFORMATION(1)
PRODUCT
PACKAGE−LEAD
PACKAGE
DESIGNATOR
SPECIFIED
TEMPERATURE
RANGE
PACKAGE
MARKING
ADS1224
TSSOP-20
PW
−40°C to +85°C
ADS1224
ORDERING
NUMBER
TRANSPORT
MEDIA, QUANTITY
ADS1224IPWT
Tape and Reel, 250
ADS1224IPWR
Tape and Reel, 2500
(1) For the most current specification and package information, refer to our web site at www.ti.com.
ABSOLUTE MAXIMUM RATINGS
over operating free-air temperature range unless otherwise noted(1)
ADS1224
UNIT
AVDD to GND
−0.3 to +6
V
DVDD to GND
−0.3 to +6
V
100, momentary
mA
Input current
10, continuous
mA
Analog input voltage to GND
−0.3 to AVDD + 0.3
V
Digital input voltage to GND
−0.3 to DVDD + 0.3
V
+150
°C
Operating Temperature Range
−55 to +125
°C
Storage Temperature Range
−60 to +150
°C
Maximum Junction Temperature
Lead Temperature (soldering, 10s)
+300
°C
(1) 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.
2
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.
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SBAS286C − JUNE 2003 − REVISED JANUARY 2009
ELECTRICAL CHARACTERISTICS
All specifications at TA = −40°C to +85°C, AVDD = +5V, DVDD = +5V, fCLK = 2MHz, and VREF = +2.5V, unless otherwise noted.
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
Analog Input
Full-scale input voltage
Absolute input voltage
Differential input impedance
Common-mode input impedance
±2VREF
AINP − AINN
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; fCLK = 2MHz
2.7
MΩ
Buffer on; fCLK = 2MHz
1.2
GΩ
Buffer off; fCLK = 2MHz
5.4
MΩ
120 (fCLK/2MHz)
Bits
SPS(1)
% of FSR(2)
System Performance
Resolution
No missing codes
24
Data rate
Integral nonlinearity (INL)
Offset error
Offset error drift
Offset error match
Gain error
Gain error drift
Gain error match
Common-mode rejection
Analog power-supply rejection
Digital power-supply rejection
Buffer off, Differential input signal, end point fit
0.0003
Buffer on, Differential input signal, end point fit
0.0006
0.0015
% of FSR
100
µV
Buffer off
20
Buffer on
20
µV
Buffer off
0.2
µV/°C
Buffer on
0.2
µV/°C
20
100
µV
Buffer off
0.004
0.025
%
Buffer on
0.008
%
Buffer off
0.00003
% of FSR/°C
Buffer on
0.00006
% of FSR/°C
Between channels
0.0005
%
Between channels
Buffer off, at DC
90
110
dB
Buffer on, at DC
90
110
dB
Buffer off, at DC, ± 10% ∆ in AVDD
95
dB
Buffer on, at DC, ± 10% ∆ in AVDD
95
dB
Buffer off, at DC, DVDD = 2.7V to 5.5V
85
dB
Buffer on, at DC, DVDD = 2.7V to 5.5V
85
dB
0.8
ppm of FSR, rms
106
mV
360
µV/°C
Noise
Temperature Sensor
Temperature sensor voltage
TA = 25°C
Temperature sensor coefficient
Voltage Reference Input
AVDD(3)
V
GND − 0.1
VREFP − 0.5
V
Buffer off
VREFN + 0.5
AVDD + 0.1
V
Negative reference input
Buffer on
GND + 0.05
VREFP − 0.5
V
Positive reference input
Buffer on
VREFN + 0.5
AVDD − 1.5
Voltage reference impedance
fCLK = 2MHz
Reference input voltage
Negative reference input
VREF = VREFP − VREFN
Buffer off
Positive reference input
0.5
2.5
500
V
kΩ
(1) SPS = samples per second.
(2) FSR = full-scale range = 4VREF.
(3) It will not be possible to reach the digital output full-scale code when VREF > AVDD/2.
3
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SBAS286C − JUNE 2003 − REVISED JANUARY 2009
ELECTRICAL CHARACTERISTICS (continued)
All specifications at TA = −40°C to +85°C, AVDD = +5V, DVDD = +5V, fCLK = 2MHz, and VREF = +2.5V, unless otherwise noted.
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
0.8 DVDD
DVDD + 0.1
V
GND − 0.1
0.2 DVDD
V
Digital Input/Output
Logic
levels
VIH
VIL
VOH
VOL
IOH = 1mA
IOL = 1mA
0.8 DVDD
V
Input leakage
CLK frequency (fCLK)
0.2 DVDD
V
±10
µA
8
MHz
30
70
%
AVDD
2.7
5.5
V
DVDD
2.7
5.5
CLK duty cycle
Power Supply
AVDD current
DVDD current
Total power dissipation
V
Standby mode