SBAS286A - JUNE 2003 - REVISED MARCH 2004
24 Bit Analog to Digital Converter
with 4 Channel Differential Input Multiplexer
ADS1224
FEATURES
D
240SPS Data Rate with 4MHz Clock
D
20-Bit Effective Resolution
D
Input Multiplexer with Four Differential
Channels
D
Pin-Selectable, High-Impedance Input Buffer
D
5V Differential Input Range
D
0.0003% INL (typ), 0.0015% INL (max)
D
Self-Calibrating
D
Simple 2-Wire Serial Interface
D
On-Chip Temperature Sensor
D
Single Conversions with Standby Mode
D
Low Current Consumption: 300
A
D
Analog Supply: 2.7V to 5.5V
D
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 ana-
log-to-digital (A/D) converter. It offers excellent perfor-
mance and low power in a TSSOP-20 package. The
ADS1224 is well-suited for demanding, high-resolution
measurements, especially in portable systems and oth-
er space-saving and power-constrained applications.
A delta-sigma 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 1
W during
Standby mode.
Mux
Digital Filter
and
Serial Interface
Modulator
VREFP VREFN
Buffer
AVDD
DVDD
GND
MUX0
AINP1
AINN1
AINP2
AINN2
AINP3
AINN3
AINP4
AINN4
CLK
DRDY/DOUT
SCLK
TEMPEN
MUX1
BUFEN
www.ti.com
Copyright
2003-2004, Texas Instruments Incorporated
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 Texas Instruments standard warranty.
Production processing does not necessarily include testing of all parameters.
ADS1224
SBAS286A - JUNE 2003 - REVISED MARCH 2004
www.ti.com
2
ORDERING INFORMATION
PRODUCT
PACKAGE-LEAD
PACKAGE
DESIGNATOR(1)
SPECIFIED
TEMPERATURE
RANGE
PACKAGE
MARKING
ORDERING
NUMBER
TRANSPORT
MEDIA, QUANTITY
ADS1224
TSSOP-20
PW
-40
C to +85
C
ADS1224
ADS1224IPWT
Tape and Reel, 250
ADS1224
TSSOP-20
PW
-40
C to +85
C
ADS1224
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
Input current
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
Maximum Junction Temperature
+150
C
Operating Temperature Range
-55 to +125
C
Storage Temperature Range
-60 to +150
C
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.
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.
ADS1224
SBAS286A - JUNE 2003 - REVISED MARCH 2004
www.ti.com
3
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
AINP - AINN
2VREF
V
Absolute input voltage
Buffer off; AINP, AINN with respect to GND
GND - 0.1
AVDD + 0.1
V
Absolute input voltage
Buffer on; AINP, AINN with respect to GND
GND + 0.05
AVDD - 1.5
V
Differential input impedance
Buffer off; fCLK = 2MHz
2.7
M
Differential input impedance
Buffer on; fCLK = 2MHz
1.2
G
Common-mode input impedance
Buffer off; fCLK = 2MHz
5.4
M
System Performance
Resolution
No missing codes
24
Bits
Data rate
120 (fCLK/2MHz)
SPS(1)
Integral nonlinearity (INL)
Buffer off, Differential input signal, end point fit
0.0003
0.0015
% of FSR
(2)
Integral nonlinearity (INL)
Buffer on, Differential input signal, end point fit
0.0006
% of FSR
Offset error
Buffer off
20
100
V
Offset error
Buffer on
20
V
Offset error drift
Buffer off
0.2
V/
C
Offset error drift
Buffer on
0.2
V/
C
Offset error match
Between channels
20
100
V
Gain error
Buffer off
0.004
0.025
%
Gain error
Buffer on
0.008
%
Gain error drift
Buffer off
0.00003
% of FSR/
C
Gain error drift
Buffer on
0.00006
% of FSR/
C
Gain error match
Between channels
0.0005
%
Common-mode rejection
Buffer off, at DC
90
110
dB
Common-mode rejection
Buffer on, at DC
90
110
dB
Analog power-supply rejection
Buffer off, at DC,
10%
in AVDD
95
dB
Analog power-supply rejection
Buffer on, at DC,
10%
in AVDD
95
dB
Digital power-supply rejection
Buffer off, at DC, DVDD = 2.7V to 5.5V
85
dB
Digital power-supply rejection
Buffer on, at DC, DVDD = 2.7V to 5.5V
85
dB
Noise
0.8
ppm of FSR, rms
Temperature Sensor
Temperature sensor voltage
TA = 25
C
106
mV
Temperature sensor coefficient
360
V/
C
Voltage Reference Input
Reference input voltage
VREF = VREFP - VREFN
0.5
2.5
AVDD(3)
V
Negative reference input
Buffer off
GND - 0.1
VREFP - 0.5
V
Positive reference input
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
V
Voltage reference impedance
fCLK = 2MHz
500
k
(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.
ADS1224
SBAS286A - JUNE 2003 - REVISED MARCH 2004
www.ti.com
4
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
UNIT
MAX
TYP
MIN
TEST CONDITIONS
Digital Input/Output
VIH
0.8 DVDD
DVDD + 0.1
V
Logic
VIL
GND - 0.1
0.2 DVDD
V
Logic
levels
VOH
IOH = 1mA
0.8 DVDD
V
levels
VOL
IOL = 1mA
0.2 DVDD
V
Input leakage
10
A
CLK frequency (fCLK)
8
MHz
CLK duty cycle
30
70
%
Power Supply
AVDD
2.7
5.5
V
DVDD
2.7
5.5
V
Standby mode
< 1
A
AVDD = 5V, normal mode, buffer off
285
A
AVDD current
AVDD = 5V, normal mode, buffer on
405
A
AVDD current
AVDD = 3V, normal mode, buffer off
265
A
AVDD = 3V, normal mode, buffer on
385
A
Standby mode
< 1
A
DVDD current
DVDD = 5V, normal mode
20
A
DVDD current
DVDD = 3V, normal mode
10
A
Total power dissipation
AVDD = DVDD = 5V, buffer off
1.5
2.25
mW
Total power dissipation
AVDD = DVDD = 3V, buffer off
0.8
mW
Temperature Range
Specified
-40
+85
C
Operating
-55
+125
C
Storage
-60
+150
C
(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.
ADS1224
SBAS286A - JUNE 2003 - REVISED MARCH 2004
www.ti.com
5
PIN ASSIGNMENTS
PW PACKAGE
TSSOP
(TOP VIEW)
DVDD
SCLK
CLK
DRDY/DOUT
MUX0
MUX1
TEMPEN
BUFEN
AINP4
AINN4
AVDD
VREFP
VREFN
GND
AINN1
AINP1
AINN2
AINP2
AINN3
AINP3
1
2
3
4
5
6
7
8
9
10
20
19
18
17
16
15
14
13
12
11
ADS1224
Terminal Functions
TERMINAL
NAME
NO.
I/O
DESCRIPTION
DVDD
1
Digital
Digital power supply
SCLK
2
Digital input
Serial clock input
CLK
3
Digital input
System clock input
DRDY/DOUT
4
Digital Ouput
Dual-purpose output:
Data Ready: indicates valid data by going low.
Data Output: outputs data, MSB first, on the rising edge of SCLK.
MUX0
5
Digital input
Selects analog input of mux, bit 0
MUX1
6
Digital input
Selects analog input of mux, bit 1
TEMPEN
7
Digital input
Selects temperature sensor input from mux
BUFEN
8
Digital input
Enables input buffer
AINP4
9
Analog input
Analog channel 4 positive input
AINN4
10
Analog input
Analog channel 4 negative input
AINP3
11
Analog input
Analog channel 3 positive input
AINN3
12
Analog input
Analog channel 3 negative input
AINP2
13
Analog input
Analog channel 2 positive input
AINN2
14
Analog input
Analog channel 2 negative input
AINP1
15
Analog input
Analog channel 1 positive input
AINN1
16
Analog input
Analog channel 1 negative input
GND
17
Analog/Digital
Analog and digital ground
VREFN
18
Analog input
Negative reference input
VREFP
19
Analog input
Positive reference input
AVDD
20
Analog
Analog power supply
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