TEXAS INSTRUMENTS ADS1224 Technical data
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of Texas Instruments
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SBAS286A − JUNE 2003 − REVISED MARCH 2004
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: 300µA
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 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 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 bu ffer 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
AINP1
AINN1
AINP2
AINN2
AINP3
AINN3
AINP4
AINN4
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Mux
MUX1 BUFEN
AVDD DVDD
Buffer
VREFP VREFN
∆Σ
Modulator
GNDMUX0
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Digital Filter
and
SerialInterface
Copyright 2003−2004, Texas Instruments Incorporated
CLK
SCLK
DRDY/DOUT
ADS1224
TSSOP-20
PW
−40°C to +85°C
ADS1224
Input current
SBAS286A − JUNE 2003 − REVISED MARCH 2004
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
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ORDERING
NUMBER
ADS1224IPWT Tape and Reel, 250
ADS1224IPWR Tape and Reel, 2500
TRANSPORT
MEDIA, QUANTITY
ABSOLUTE MAXIMUM RATINGS
over operat i n g f ree-air temperature range unless otherwise noted
ADS1224 UNIT
AVDD to GND −0.3 to +6 V
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 DVDD + 0.3 V
Maximum Junction Temperature +150 °C
Operating Temperature Range −55 to +125 °C
Storage Temperature Range −60 to +150 °C
Lead Tem perature (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 , an d
functional operation of the device at these or any other conditions
beyond those specified is not implied.
(1)
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 t o damage because very small parametric changes could
cause the device not to meet its published specifications.
2
Absolute input voltage
Differential input impedance
Integral nonlinearity (INL)
Offset error
Offset error drift
Gain error
Gain error drift
Common-mode rejection
Analog power-supply rejection
Digital power-supply rejection
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SBAS286A − JUNE 2003 − REVISED MARCH 2004
ELECTRICAL CHARACTERISTICS
All specifications at TA = −40°C to +85°C, AVDD = +5V, DVDD = +5V, f
PARAMETER TEST CONDITIONS MIN TYP MAX UNIT
Analog Input
Full-scale input voltage AINP − AINN ±2V
Buffer off; AINP, AINN with respect to GND GND − 0.1 A VDD + 0.1 V
Buffer on; AINP, AINN with respect to GND GND + 0.05 AVDD − 1.5 V
Buffer off; f
Buffer on; f
Common-mode input impedance Buffer off; f
System Performance
Resolution No missing codes 24 Bits
Data rate 120 (f
Buffer off, Differential input signal, end point fit 0.0003 0.0015 % of FSR
Buffer on, Differential input signal, end point fit 0.0006 % of FSR
Buffer off 20 100 µV
Buffer on 20 µV
Buffer off 0.2 µV/°C
Buffer on 0.2 µV/°C
Offset error match Between channels 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
Gain error match Between channels 0.0005 %
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
Noise 0.8 ppm of FSR, rms
Temperature Sensor
Temperature sensor voltage TA = 25°C 106 mV
Temperature sensor coefficient 360 µV/°C
Voltage Reference Input
Reference input voltage V
Negative reference input Buffer off GND − 0.1 VREFP − 0.5 V
Positive reference input Buffer off VREFN + 0.5 AV DD + 0.1 V
Negative reference input Buffer on GND + 0.05 VREFP − 0.5 V
Positive reference input Buffer on VREFN + 0.5 AVD D − 1.5 V
Voltage reference impedance f
(1)
SPS = samples per second.
(2)
FSR = full-scale range = 4V
(3)
It will not be possible to reach the digital output full-scale code when V
REF
.
= VREFP − VREFN 0.5 2.5 AVDD
REF
= 2MHz 500 kΩ
CLK
= 2MHz 2.7 MΩ
CLK
= 2MHz 1.2 GΩ
CLK
= 2MHz 5.4 MΩ
CLK
= 2MHz, and V
CLK
> AVDD/2.
REF
= +2.5V , unless otherwise noted.
REF
REF
/2MHz) SPS
CLK
(3)
V
(1)
(2)
V
3
Logic
Logic
levels
AVDD current
DVDD current
Total power dissipation
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SBAS286A − JUNE 2003 − REVISED MARCH 2004
ELECTRICAL CHARACTERISTICS (continued)
All specifications at TA = −40°C to +85°C, AVDD = +5V, DVDD = +5V, f
PARAMETER UNITMAXTYPMINTEST CONDITIONS
Digital Input/Output
V
IH
V
IL
levels
Input leakage ±10 µA
CLK frequency (f
CLK duty cycle 30 70 %
Power Supply
AVDD 2.7 5.5 V
DVDD 2.7 5.5 V
AVDD current
DVDD current
Temperature Range
Specified −40 +85 °C
Operating −55 +125 °C
Storage −60 +150 °C
(1)
SPS = samples per second.
(2)
FSR = full-scale range = 4V
(3)
It will not be possible to reach the digital output full-scale code when V
V
OH
V
OL
) 8 MHz
CLK
IOH = 1mA 0.8 DVDD V
IOL = 1mA 0.2 DVDD V
Standby mode < 1 µA
AVDD = 5V, normal mode, buffer off 285 µA
AVDD = 5V, normal mode, buffer on 405 µA
AVDD = 3V, normal mode, buffer off 265 µA
AVDD = 3V, normal mode, buffer on 385 µA
Standby mode < 1 µA
DVDD = 5V , normal mode 20 µA
DVDD = 3V , normal mode 10 µA
AVDD = DVDD = 5V, buffer of f 1.5 2.25 mW
AVDD = DVDD = 3V, buffer of f 0.8 mW
.
REF
= 2MHz, and V
CLK
> AVDD/2.
REF
= +2.5V , unless otherwise noted.
REF
0.8 DVDD DVDD + 0.1 V
GND − 0.1 0.2 DVDD V
4
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PIN ASSIGNMENTS
SBAS286A − JUNE 2003 − REVISED MARCH 2004
PW PACKAGE
TSSOP
(TOP VIEW)
DVDD
SCLK
CLK
DRDY/DOUT
MUX0
MUX1
TEMPEN
BUFEN
AINP4
AINN4
10
1
2
3
4
5
6
7
8
9
ADS1224
20
19
18
17
16
15
14
13
12
11
AVDD
VREFP
VREFN
GND
AINN1
AINP1
AINN2
AINP2
AINN3
AINP3
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
5
ANALOG CURRENT vs TEMPERATURE
ANALOG CURRENT vs TEMPERATURE
DIGITALCURRENT vs TEMPERATURE
ANALOG CURRENT vs SUPPLY VOLTAGE
DIGITALCURRENT vs SUPPLY VOLTAGE
TEMPERATURE SENSOR VOLTAGE vs TEMPERATURE
SBAS286A − JUNE 2003 − REVISED MARCH 2004
TYPICAL CHARACTERISTICS
At TA = −40°C to +85°C, AVDD = +5V, DVDD = +5V, f
= 2MHz, and V
CLK
= +2.5V , unless otherwise noted.
REF
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350
Buffer Off
325
f
300
A)
µ
275
Current (
250
225
200
−
55
CLK
f
−
25 35 65 95 125
f
=4MHz,AVDD=5V
CLK
=2MHz,AVDD=5V
=4MHz,AVDD=3V
CLK
5
Temperature (_C)
f
=2MHz,AVDD=3V
CLK
Figure 1
50
40
f
=4MHz,AVDD=5V
A)
30
µ
Current(
20
10
f
=2MHz,AVDD=5V
CLK
CLK
f
=4MHz,AVDD=3V
CLK
500
Buffer On
f
=2MHz,AVDD=5V
450
A)
µ
400
Current (
350
300
f
CLK
−
55
CLK
=4MHz,AVDD=3V
−
25 35 65 95 125
5
f
= 4MHz, AVDD = 5V
CLK
f
=2MHz,AVDD=3V
CLK
Temperature (_C)
Figure 2
450
f
=2MHz
CLK
400
A)
350
µ
300
Current (
250
Buffer On
Buffer Off
f
=2MHz,AVDD=3V
CLK
0
−
−
55
25 35 65 95 125
5
Temperature (_C)
Figure 3
50
40
A)
30
µ
Current(
f
=4MHz
CLK
20
f
=2MHz
CLK
10
0
3.53.0 4.0 4.5 5.0 5.52.5
Supply Voltage (V)
Figure 5
200
3.53.0 4.0 4.5 5.0 5.52.5
Supply Voltage (V)
Figure 4
150
140
130
120
110
100
90
80
Temperature Sensor Voltage (mV)
70
−
−
25 35 65 95 125
55
5
Temperature (_C)
Figure 6
6
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INTEGRAL NONLINEARITY vs INPUT VOLTAGE
INL (% of FSR)
INTEGRAL NONLINEARITY vs INPUT VOLTAGE
INL (% of FS R )
INTEGRAL NONLINEARITY vs INPUT VOLTAGE
INL (% o f FSR )
INTEGRAL NONLINEARITY vs INPUT VOLTAGE
INL (% o f F S R)
NOISE vs INPUT VOLTAGE
NOISE vs INPUT VOLTAGE
TYPICAL CHARACTERISTICS (CONTINUED)
At TA = −40°C to +85°C, AVDD = +5V, DVDD = +5V, f
= 2MHz, and V
CLK
SBAS286A − JUNE 2003 − REVISED MARCH 2004
= +2.5V , unless otherwise noted.
REF
0.0006
0.0004
0.0002
−
0.0002
−
0.0004
−
0.0006
−
0.0008
−
0.0010
0.0015
0.0010
0.0005
−
0.0005
f
=2MHz
CLK
−40_
C
+85_C
−
3
+25_C
−2−
1012345
Input Voltage, VIN(V)
0
−
−
4
5
Buffer Off
Figure 7
f
=4MHz
CLK
Buffer Off
−40_
C
+25_C
0
+85_C
0.0010
0.0008
0.0006
0.0004
0.0002
−
0.0002
−
0.0004
−
0.0006
−
0.0008
−
0.0010
0.0015
0.0010
0.0005
−
0.0005
−40_
C
+25_C
0
+85_C
−
−
−
3.5
2.5
−
1.5
0.5 0.5 1.5 2.5 3.5
Input Voltage, V
IN
Figure 8
−40_
C
+25_C
+85_C
0
(V)
f
CLK
Buffer On
f
CLK
Buffer On
=2MHz
=4MHz
−
−
0.0010
−
0.0015
−
5
−
−
4
3
−2−
10 1 2 3 4 5
Input Voltage, V
(V)
IN
Figure 9
1.5
f
=2MHz
CLK
Buffer On
1.0
0.5
Noise (ppm of FSR, rms)
0
3.5−3.0−2.5−2.0−1.5−1.0−0.5
−
0
0.5
Input Voltage, VIN(V)
1.0
1.5
2.0
2.5
3.0
3.5
Figure 11
0.0010
−
0.0015
Noise (ppm of FSR, rms)
1.5
1.0
0.5
−
3.5
0
−
f
=2MHz
CLK
Buffer Off
5
−
−
2.5
−
1.5
0.5 0.5 1.5 2.5 3.5
Input Voltage, V
(V)
IN
Figure 10
−
3
−
1135
Input Voltage, VIN(V)
Figure 12
7
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