ADS1218Y/2K [TI]
8-CH 24-BIT DELTA-SIGMA ADC, SERIAL ACCESS, PQFP48, PLASTIC, TQFP-48;
| 型号： | ADS1218Y/2K |
| 厂家： | 
TEXAS INSTRUMENTS |
| 描述： | 8-CH 24-BIT DELTA-SIGMA ADC, SERIAL ACCESS, PQFP48, PLASTIC, TQFP-48 转换器 |
| 文件： | 总32页 (文件大小：1061K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
ꢇ ꢍꢚ ꢛꢀ ꢀꢁ
www.ti.com
SBAS286C − JUNE 2003 − REVISED JANUARY 2009
ꢀ
ꢁ
ꢂ
ꢃ
ꢄ
ꢅ
ꢆ
ꢇ
ꢈ
ꢉ
ꢊ
ꢋ
ꢌ
ꢂ
ꢅ
ꢋ
ꢂ
ꢍ
ꢄ
ꢌ
ꢄ
ꢅ
ꢉ
ꢊ
ꢆ
ꢎ
ꢋ
ꢈ
ꢅ
ꢏꢐ ꢑ ꢅ ꢐꢑ
ꢘ ꢗꢊ ꢅ ꢄꢖ ꢊꢐ ꢙꢐꢑ
ꢒ
ꢄ
ꢅ
ꢓ
ꢁ
ꢂ
ꢎ
ꢓ
ꢉ
ꢈ
ꢈ
ꢐ
ꢊ
ꢍ
ꢄ
ꢔ
ꢔ
ꢐ
ꢑ
ꢐ
ꢈ
ꢅ
ꢄ
ꢉ
ꢊ
ꢕ
ꢈ
ꢖ
ꢗ
FEATURES
DESCRIPTION
D
D
D
240SPS Data Rate with 4MHz Clock
20-Bit Effective Resolution
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.
Input Multiplexer with Four Differential
Channels
D
D
D
D
D
D
D
D
D
D
Pin-Selectable, High-Impedance Input Buffer
5V Differential Input Range
A delta-sigma (∆Σ) modulator and digital filter form the
basis of the A/D converter. The analog modulator has
0.0003% INL (typ), 0.0015% INL (max)
Self-Calibrating
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.
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
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.
Digital Supply: 2.7V to 5.5V
APPLICATIONS
D
D
D
D
Hand-Held Instrumentation
Portable Medical Equipment
Industrial Process Control
Weigh Scales
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
Digital Filter
and
Serial Interface
SCLK
∆Σ
Modulator
Mux
Buffer
DRDY/DOUT
AINP3
AINN3
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.
ꢜꢝ ꢞ ꢍꢟ ꢎ ꢠꢕ ꢞꢡ ꢍ ꢇꢠꢇ ꢄꢈ ꢔꢋ ꢑ ꢢꢉ ꢅꢄꢋꢈ ꢄꢣ ꢤꢗ ꢑ ꢑ ꢐꢈꢅ ꢉꢣ ꢋꢔ ꢖꢗꢥ ꢊꢄꢤ ꢉꢅꢄ ꢋꢈ ꢦꢉ ꢅꢐꢧ ꢜꢑ ꢋꢦꢗ ꢤꢅꢣ
ꢤ ꢋꢈ ꢔꢋꢑ ꢢ ꢅꢋ ꢣ ꢖꢐ ꢤ ꢄ ꢔꢄ ꢤ ꢉ ꢅꢄ ꢋꢈꢣ ꢖ ꢐꢑ ꢅꢓꢐ ꢅꢐ ꢑ ꢢꢣ ꢋꢔ ꢠꢐꢙ ꢉꢣ ꢕꢈꢣ ꢅꢑ ꢗꢢ ꢐꢈꢅ ꢣ ꢣꢅ ꢉꢈꢦ ꢉꢑ ꢦ ꢒ ꢉꢑ ꢑ ꢉ ꢈꢅꢨꢧ
ꢜꢑ ꢋ ꢦꢗꢤ ꢅ ꢄꢋ ꢈ ꢖꢑ ꢋ ꢤ ꢐ ꢣ ꢣ ꢄꢈ ꢌ ꢦꢋ ꢐ ꢣ ꢈꢋꢅ ꢈꢐ ꢤꢐ ꢣꢣ ꢉꢑ ꢄꢊ ꢨ ꢄꢈꢤ ꢊꢗꢦ ꢐ ꢅꢐ ꢣꢅꢄ ꢈꢌ ꢋꢔ ꢉꢊ ꢊ ꢖꢉ ꢑ ꢉꢢ ꢐꢅꢐ ꢑ ꢣꢧ
Copyright 2003−2008, Texas Instruments Incorporated
www.ti.com
ꢇꢍ ꢚꢛ ꢀ ꢀ ꢁ
www.ti.com
SBAS286C − JUNE 2003 − REVISED JANUARY 2009
(1)
ORDERING INFORMATION
SPECIFIED
TEMPERATURE
RANGE
PACKAGE
DESIGNATOR
PACKAGE
MARKING
ORDERING
NUMBER
TRANSPORT
MEDIA, QUANTITY
PRODUCT
PACKAGE−LEAD
ADS1224IPWT
ADS1224IPWR
Tape and Reel, 250
Tape and Reel, 2500
ADS1224
TSSOP-20
PW
−40°C to +85°C
ADS1224
(1)
For the most current specification and package information, refer to our web site at www.ti.com.
This integrated circuit can be damaged by ESD. Texas
Instruments recommends that all integrated circuits be
handledwith appropriate precautions. Failure to observe
ABSOLUTE MAXIMUM RATINGS
over operating free-air temperature range unless otherwise noted
(1)
proper handling and installation procedures can cause damage.
ADS1224
−0.3 to +6
UNIT
AVDD to GND
DVDD to GND
V
V
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.
−0.3 to +6
100, momentary
10, continuous
−0.3 to AVDD + 0.3
−0.3 to DVDD + 0.3
+150
mA
mA
V
Input current
Analog input voltage to GND
Digital input voltage to GND
Maximum Junction Temperature
Operating Temperature Range
Storage Temperature Range
Lead Temperature (soldering, 10s)
V
°C
°C
°C
°C
−55 to +125
−60 to +150
+300
(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
ꢇ ꢍꢚ ꢛꢀ ꢀꢁ
www.ti.com
SBAS286C − JUNE 2003 − REVISED JANUARY 2009
ELECTRICAL CHARACTERISTICS
All specifications at T = −40°C to +85°C, AVDD = +5V, DVDD = +5V, f
= 2MHz, and V
REF
= +2.5V, unless otherwise noted.
A
CLK
PARAMETER
Analog Input
TEST CONDITIONS
MIN
TYP
MAX
UNIT
Full-scale input voltage
AINP − AINN
2V
REF
V
V
Buffer off; AINP, AINN with respect to GND
Buffer on; AINP, AINN with respect to GND
GND − 0.1
AVDD + 0.1
AVDD − 1.5
Absolute input voltage
GND + 0.05
V
Buffer off; f
Buffer on; f
Buffer off; f
= 2MHz
= 2MHz
= 2MHz
2.7
1.2
5.4
MΩ
GΩ
MΩ
CLK
CLK
CLK
Differential input impedance
Common-mode input impedance
System Performance
Resolution
No missing codes
24
Bits
(1)
SPS
Data rate
120 (f /2MHz)
CLK
(2)
Buffer off, Differential input signal, end point fit
Buffer on, Differential input signal, end point fit
Buffer off
0.0003
0.0006
20
0.0015
100
% of FSR
Integral nonlinearity (INL)
Offset error
% of FSR
µV
Buffer on
20
µV
Buffer off
0.2
µV/°C
Offset error drift
Offset error match
Gain error
Buffer on
0.2
µV/°C
Between channels
20
100
µV
Buffer off
0.004
0.008
0.00003
0.00006
0.0005
110
0.025
%
Buffer on
%
Buffer off
% of FSR/°C
Gain error drift
Buffer on
% of FSR/°C
Gain error match
Between channels
%
Buffer off, at DC
90
90
dB
Common-mode rejection
Buffer on, at DC
110
dB
Buffer off, at DC, 10% ∆ in AVDD
Buffer on, at DC, 10% ∆ in AVDD
Buffer off, at DC, DVDD = 2.7V to 5.5V
Buffer on, at DC, DVDD = 2.7V to 5.5V
95
dB
Analog power-supply rejection
Digital power-supply rejection
95
dB
85
dB
dB
85
Noise
0.8
ppm of FSR, rms
Temperature Sensor
Temperature sensor voltage
Temperature sensor coefficient
Voltage Reference Input
Reference input voltage
Negative reference input
Positive reference input
Negative reference input
Positive reference input
Voltage reference impedance
T
= 25°C
106
360
mV
A
µV/°C
(3)
AVDD
V
= VREFP − VREFN
0.5
2.5
V
V
REF
Buffer off
Buffer off
Buffer on
Buffer on
GND − 0.1
VREFN + 0.5
GND + 0.05
VREFN + 0.5
VREFP − 0.5
AVDD + 0.1
VREFP − 0.5
AVDD − 1.5
V
V
V
f
= 2MHz
500
kΩ
CLK
(1)
(2)
(3)
SPS = samples per second.
FSR = full-scale range = 4V
REF
It will not be possible to reach the digital output full-scale code when V
.
> AVDD/2.
REF
3
ꢇꢍ ꢚꢛ ꢀ ꢀ ꢁ
www.ti.com
SBAS286C − JUNE 2003 − REVISED JANUARY 2009
ELECTRICAL CHARACTERISTICS (continued)
All specifications at T = −40°C to +85°C, AVDD = +5V, DVDD = +5V, f
= 2MHz, and V = +2.5V, unless otherwise noted.
REF
A
CLK
PARAMETER
Digital Input/Output
TEST CONDITIONS
MIN
TYP
MAX
UNIT
V
V
V
V
0.8 DVDD
GND − 0.1
0.8 DVDD
DVDD + 0.1
0.2 DVDD
V
V
IH
Logic
levels
IL
I
I
= 1mA
= 1mA
V
OH
OL
OH
OL
0.2 DVDD
V
Input leakage
10
8
µA
MHz
%
CLK frequency (f
CLK duty cycle
Power Supply
AVDD
)
CLK
30
70
2.7
2.7
5.5
5.5
V
V
DVDD
Standby mode
< 1
285
405
265
385
< 1
20
µA
µA
µA
µA
µA
µA
µA
µA
mW
mW
AVDD = 5V, normal mode, buffer off
AVDD = 5V, normal mode, buffer on
AVDD = 3V, normal mode, buffer off
AVDD = 3V, normal mode, buffer on
Standby mode
AVDD current
DVDD current
DVDD = 5V, normal mode
DVDD = 3V, normal mode
10
AVDD = DVDD = 5V, buffer off
AVDD = DVDD = 3V, buffer off
1.5
0.8
2.25
Total power dissipation
Temperature Range
Specified
−40
−55
−60
+85
+125
+150
°C
°C
°C
Operating
Storage
(1)
(2)
(3)
SPS = samples per second.
FSR = full-scale range = 4V
REF
It will not be possible to reach the digital output full-scale code when V
.
> AVDD/2.
REF
4
ꢇ ꢍꢚ ꢛꢀ ꢀꢁ
www.ti.com
SBAS286C − JUNE 2003 − REVISED JANUARY 2009
PIN ASSIGNMENTS
PW PACKAGE
TSSOP
(TOP VIEW)
DVDD
SCLK
1
2
3
4
5
6
7
8
9
20 AVDD
19
18
17
VREFP
VREFN
GND
CLK
DRDY/DOUT
MUX0
16 AINN1
15 AINP1
ADS1224
MUX1
14
13
12
TEMPEN
BUFEN
AINP4
AINN2
AINP2
AINN3
AINN4 10
11 AINP3
Terminal Functions
TERMINAL
NAME
NO.
I/O
DESCRIPTION
DVDD
1
Digital
Digital power supply
SCLK
2
3
4
Digital input
Digital input
Digital Ouput
Serial clock input
CLK
System clock input
Dual-purpose output:
DRDY/DOUT
Data Ready: indicates valid data by going low.
Data Output: outputs data, MSB first, on the rising edge of SCLK.
Selects analog input of mux, bit 0
Selects analog input of mux, bit 1
Selects temperature sensor input from mux
Enables input buffer
MUX0
MUX1
TEMPEN
BUFEN
AINP4
AINN4
AINP3
AINN3
AINP2
AINN2
AINP1
AINN1
GND
5
Digital input
Digital input
Digital input
Digital input
Analog input
Analog input
Analog input
Analog input
Analog input
Analog input
Analog input
Analog input
Analog/Digital
Analog input
Analog input
Analog
6
7
8
9
Analog channel 4 positive input
Analog channel 4 negative input
Analog channel 3 positive input
Analog channel 3 negative input
Analog channel 2 positive input
Analog channel 2 negative input
Analog channel 1 positive input
Analog channel 1 negative input
Analog and digital ground
10
11
12
13
14
15
16
17
18
19
20
VREFN
VREFP
AVDD
Negative reference input
Positive reference input
Analog power supply
5
ꢇꢍ ꢚꢛ ꢀ ꢀ ꢁ
www.ti.com
SBAS286C − JUNE 2003 − REVISED JANUARY 2009
TYPICAL CHARACTERISTICS
At T = −40°C to +85°C, AVDD = +5V, DVDD = +5V, f
CLK
= 2MHz, and V = +2.5V, unless otherwise noted.
REF
A
ANALOG CURRENT vs TEMPERATURE
Buffer Off
ANALOG CURRENT vs TEMPERATURE
Buffer On
350
325
300
275
250
225
200
500
fCLK = 4MHz, AVDD = 5V
fCLK = 2MHz, AVDD = 5V
fCLK = 4MHz, AVDD = 5V
450
fCLK = 2MHz, AVDD = 5V
fCLK = 4MHz, AVDD = 3V
400
350
300
fCLK = 2MHz, AVDD = 3V
fCLK = 2MHz, AVDD = 3V
fCLK = 4MHz, AVDD = 3V
−
−
25
55
5
35
65
95
125
−
−
25
55
5
35
65
95
125
_
Temperature ( C)
_
Temperature ( C)
Figure 1
Figure 2
DIGITAL CURRENT vs TEMPERATURE
ANALOG CURRENT vs SUPPLY VOLTAGE
450
400
350
300
250
200
50
40
30
20
10
0
fCLK = 2MHz
Buffer On
fCLK = 4MHz, AVDD = 5V
fCLK = 2MHz, AVDD = 5V
Buffer Off
fCLK = 4MHz, AVDD = 3V
fCLK = 2MHz, AVDD = 3V
2.5
3.0
3.5
4.0
4.5
5.0
5.5
−
−
25
55
5
35
65
95
125
_
Supply Voltage (V)
Temperature ( C)
Figure 3
Figure 4
DIGITAL CURRENT vs SUPPLY VOLTAGE
TEMPERATURE SENSOR VOLTAGE vs TEMPERATURE
50
40
30
20
10
0
150
140
130
120
110
100
90
fCLK = 4MHz
fCLK = 2MHz
80
70
−
−
25
2.5
3.0
3.5
4.0
4.5
5.0
5.5
55
5
35
65
95
125
Supply Voltage (V)
_
Temperature ( C)
Figure 5
Figure 6
6
ꢇ ꢍꢚ ꢛꢀ ꢀꢁ
www.ti.com
SBAS286C − JUNE 2003 − REVISED JANUARY 2009
TYPICAL CHARACTERISTICS (CONTINUED)
At T = −40°C to +85°C, AVDD = +5V, DVDD = +5V, f
CLK
= 2MHz, and V = +2.5V, unless otherwise noted.
REF
A
INTEGRAL NONLINEARITY vs INPUT VOLTAGE
INTEGRAL NONLINEARITY vs INPUT VOLTAGE
0.0010
0.0006
0.0004
0.0002
0
fCLK = 2MHz
Buffer On
fCLK = 2MHz
Buffer Off
0.0008
0.0006
0.0004
0.0002
0
−
_
40 C
−
_
40 C
_
+25 C
_
+25 C
−
−
−
−
−
0.0002
0.0004
0.0006
0.0008
0.0010
_
+85 C
_
+85 C
−
−
−
−
−
0.0002
0.0004
0.0006
0.0008
0.0010
−
−
−
−
0.5
−
−
−
−
−
1
5
4
3
2
0
1
2
3
4
5
3.5
2.5
1.5
0.5
1.5
2.5
3.5
Input Voltage, VIN (V)
Input Voltage, VIN (V)
Figure 7
Figure 8
INTEGRAL NONLINEARITY vs INPUT VOLTAGE
fCLK = 4MHz
Buffer Off
INTEGRAL NONLINEARITY vs INPUT VOLTAGE
0.0015
0.0010
0.0005
0
0.0015
0.0010
0.0005
0
fCLK = 4MHz
Buffer On
−
_
40 C
_
−
_
+25 C
40 C
_
+25 C
_
+85 C
_
+85 C
−
−
−
0.0005
0.0010
0.0015
−
−
−
0.0005
0.0010
0.0015
−
−
−
−
0.5
3.5
2.5
1.5
0.5
1.5
2.5
3.5
−
−
−
−
−
1
5
4
3
2
0
1
2
3
4
5
Input Voltage, VIN (V)
Input Voltage, VIN (V)
Figure 9
Figure 10
NOISE vs INPUT VOLTAGE
NOISE vs INPUT VOLTAGE
1.5
1.0
0.5
0
fCLK = 2MHz
Buffer On
1.5
1.0
0.5
0
fCLK = 2MHz
Buffer Off
−
−
−
1
5
3
1
3
5
Input Voltage, VIN (V)
Input Voltage, VIN (V)
Figure 11
Figure 12
7
ꢇꢍ ꢚꢛ ꢀ ꢀ ꢁ
www.ti.com
SBAS286C − JUNE 2003 − REVISED JANUARY 2009
as shown in Table 1. The ADS1224 accepts differential
input signals, but can also measure unipolar signals.
When measuring unipolar (or single-ended signals)
with respect to ground, connect the negative input
(AINNx) to ground and connect the input signal to the
positive input (AINPx). Note that when the ADS1224 is
configured this way, only half of the converter full-scale
range is used since only positive digital output codes
are produced. An input buffer can be selected to
increase the input impedance of the A/D converter with
the BUFEN pin.
OVERVIEW
The ADS1224 is an A/D converter comprised of a
delta-sigma modulator followed by a digital filter. A mux
allows for one of four input channels to be selected. A
buffer can also be selected to increase the input
impedance. The modulator measures the differential
input signal V = (AINP – AINN) against the differential
IN
REF
reference V
= (VREFP – VREFN). Figure 13 shows
a conceptual diagram of the device. The differential
reference is scaled internally so that the full-scale input
range is 2V
. The digital filter receives the modulator
REF
signal and provides a low-noise digital output. A 2-wire
serial interface indicates conversion completion and
provides the user with the output data.
Table 1. Input Channel selection with
MUX0 and MUX1
DIGITAL PINS
SELECTED ANALOG INPUTS
POSITIVE INPUT NEGATIVE INPUT
AINP1 AINN1
ANALOG INPUTS (AINPx, AINNx)
MUX1
MUX0
0
0
1
1
0
1
0
1
The input signal to be measured is applied to the input
pins AINPx and AINNx. The positive internal input is
generalized as AINP, and the negative internal input is
generalized as AINN. The signal is selected though the
input mux, which is controlled by pins MUX0 and MUX1,
AINP2
AINP3
AINP4
AINN2
AINN3
AINN4
TEMPEN
VREFP VREFN
−
+
Temp
Sensor
Σ
CLK
VREF
AINP1
AINN1
2
2VREF
Digital
Filter
and
Serial
Interface
AINP2
AINP
SCLK
VIN
AINN2
Mux
∆Σ
Modulator
Buffer
Σ
AINP3
AINN
DRDY/DOUT
AINN3
AINP4
AINN4
MUX0 MUX1
BUFEN
Figure 13. Conceptual Diagram of the ADS1224
8
ꢇ ꢍꢚ ꢛꢀ ꢀꢁ
www.ti.com
SBAS286C − JUNE 2003 − REVISED JANUARY 2009
Analog Input Measurement without the Input Buffer
With the buffer disabled by setting the BUFEN pin low, the
ADS1224 measures the input signal using internal
capacitors that are continuously charged and discharged.
Figure 14 shows a simplified schematic of the ADS1224
input circuitry, with Figure 15 showing the on/off timings of
AVDD/2
(1)
Ω
Ω
ZeffA = tSAMPLE/CA1 = 6M
AINPx
AINNx
(1)
Ω
ZeffB = tSAMPLE/CB = 3M
the switches. The S switches close during the input
1
sampling phase. With S1 closed, C charges to AINP,
A1
(1)
ZeffA = tSAMPLE/CA2 = 6M
C
charges to AINN, and C charges to (AINP – AINN).
A2
B
For the discharge phase, S opens first and then S
AVDD/2
NOTE: (1) fCLK = 2MHz.
1
2
closes. C and C discharge to approximately AVDD/2
A1
B
A2
and
C
discharges to 0V. This two-phase
sample/discharge cycle repeats with a frequency of
Figure 16. Effective Analog Input Impedances
with the Buffer Off
f
/32 (62.5kHz for f
= 2MHz).
CLK
CLK
ESD diodes protect the inputs. To keep these diodes
from turning on, make sure the voltages on the input
pins do not go below GND by more than 100mV, and
likewise do not exceed AVDD by 100mV:
ESD Protection
AVDD
AVDD/2
CA1
3pF
S2
S1
S1
GND – 100mV < (AINP, AINN) < AVDD + 100mV
AINP
AINPx
Analog Input Measurement with the Input Buffer
When the buffer is enabled by setting the BUFEN pin
high, a low-drift, chopper-stabilized input buffer is used
to achieve very high input impedance. The buffer
charges the input sampling capacitors, thus removing
the load from the measurement. Because the input
buffer is chopper-stabilized, the charging of parasitic
capacitances causes the charge to be carried away, as
if by resistance. The input impedance can be modeled
by a single resistor, as shown in Figure 17. The
CB
6pF
Mux
AINN
AINNx
S2
CA2
3pF
AVDD
AVDD/2
Figure 14. Simplified Input Structure with the
Buffer Turned Off
impedance scales inversely with f
frequency, as in
CLK
the nonbuffered case. Note that during standby mode,
the buffer must be disabled to prevent loading of the
inputs.
tSAMPLE = 32/fCLK
ON
S1
OFF
ON
AINP
S2
OFF
(1)
Ω
1.2G
AINN
Figure 15. S and S Switch Timing for Figure 14
1
2
NOTE: (1) fCLK = 2MHz.
The constant charging of the input capacitors presents
a load on the inputs that can be represented by effective
impedances. Figure 16 shows the input circuitry with
the capacitors and switches of Figure 14 replaced by
their effective impedances. These impedances scale
Figure 17. Effective Analog Input Impedances
with the Buffer On
Note also that the analog inputs (listed in the Electrical
Characteristics table as Absolute Input Range) must
remain between GND + 0.05V to AVDD − 1.5V.
Exceeding this range degrades linearity and results in
performance outside the specified limits.
inversely with f
frequency. For example, if f
CLK
CLK
frequency is reduced by a factor of 2, the impedances
will double.
9
ꢇꢍ ꢚꢛ ꢀ ꢀ ꢁ
www.ti.com
SBAS286C − JUNE 2003 − REVISED JANUARY 2009
TEMPERATURE SENSOR
VOLTAGE REFERENCE INPUTS
(VREFP, VREFN)
The voltage reference used by the modulator is
generated from the voltage difference between VREFP
On-chip diodes provide temperature-sensing capabili-
ty. By setting the TEMPEN pin high, the selected analog
inputs are disconnected and the inputs to the A/D
converter are connected to the anodes of two diodes
scaled to 1x and 64x in current and size inside the mux,
as shown in Figure 18. By measuring the difference in
voltage of these diodes, temperature changes can be
inferred from a baseline temperature. Typically, the
difference in diode voltages is 106mV at 25°C, with a
temperature coefficient of 360µV/°C. A similar structure
is used in the MSC1210 for temperature measurement.
For more information, see TI application report
SBAA100, Using the MSC121x as a High-Precision
Intelligent Temperature Sensor, available for download
at www.ti.com.
and VREFN: V
= VREFP – VREFN. The reference
REF
inputs use a structure similar to that of the analog
inputs. A simplified diagram of the circuitry on the
reference inputs is shown in Figure 19. The switches
and capacitors can be modeled with an effective
impedance of:
tsample
ǒ Ǔń16pF + 500kW
2
where f
= 2MHz.
CLK
VREFP
VREFN
TEMPEN
AVDD
AVDD
AVDD
ESD
Protection
8I
1I
Self Gain Cal
16pF
AINP
AINN
(1)
Ω
Zeff = 500k
AINN
AINP
1X
8X
(1) fCLK = 2MHz
AINP1
AINN1
AINP2
AINN2
AINP3
AINN3
AINP4
AINN4
Figure 19. Simplified Reference input Circuitry
ESD diodes protect the reference inputs. To prevent
these diodes from turning on, make sure the voltages
on the reference pins do not go below GND by more
than 100mV, and likewise, do not exceed AVDD by
100mV:
GND – 100mV < (VREFP, VREFN) < AVDD + 100mV
During self gain calibration, all the switches in the input
multiplexer are opened, VREFN is internally connected to
AINN, and VREFP is connected to AINP. The input buffer
may be disabled or enabled during calibration. When the
buffer is disabled, the reference pins will be driving the
circuitry shown in Figure 9 during self gain calibration,
resulting in increased loading. To prevent this additional
loading from introducing gain errors, make sure the
circuitry driving the reference pins has adequate drive
capability. When the buffer is enabled, the loading on the
reference pins will be much less, but the buffer will limit the
MUX0
MUX1
Figure 18. Measurement of the Temperature
Sensor in the Input Multiplexer
10
ꢇ ꢍꢚ ꢛꢀ ꢀꢁ
www.ti.com
SBAS286C − JUNE 2003 − REVISED JANUARY 2009
allowable voltage range on VREFP and VREFN during
self or self gain calibration as the reference pins must
remain within the specified input range of the buffer in
order to establish proper gain calibration.
the pin can be forced high with an additional SCLK. It will
then stay high until new data is ready. This is useful
when polling on the status of DRDY/DOUT to determine
when to begin data retrieval.
For best performance, V
should be AVDD/2, but it can
REF
be raised as high as AVDD. When V
exceeds
SERIAL CLOCK INPUT (SCLK)
REF
AVDD/2, it is not possible to reach the full-scale digital
output value corresponding to 2V , since this requires
This digital input shifts serial data out with each rising
edge. As with CLK, this input may be driven with 5V
logic regardless of the DVDD or AVDD voltage. There
is hysteresis built into this input, but care should still be
taken to ensure a clean signal. Glitches or slow-rising
signals can cause unwanted additional shifting. For this
reason, it is best to make sure the rise-and-fall times of
SCLK are less than 50ns.
REF
the analog inputs to exceed the power supplies. For
example, if V = AVDD = 5V, the positive full-scale
REF
signal is 10V. The maximum positive input signal that can
be supplied before the ESD diodes turn on is when AINP
= 5.1V and AINN = –0.1V, resulting in V = 5.2V.
IN
Therefore, it is not possible to reach the positive (or
negative) full-scale readings in this configuration. The
digital output codes are limited to approximately one half
of the entire range. For best performance, bypass the
voltage reference inputs with a 0.1µF capacitor between
VREFP and VREFN. Place the capacitor as close as
possible to the pins.
FREQUENCY RESPONSE
The ADS1224 frequency response for f
= 2MHz is
CLK
shown in Figure 20. The frequency response repeats at
multiples of the modulator sampling frequency of
62.5kHz. The overall response is that of a low-pass filter
with a −3db cutoff frequency of 31.5Hz. As shown, the
ADS1224 does a good job attenuating out to 60kHz. For
the best resolution, limit the input bandwidth to less than
this value to keep higher frequency noise from affecting
performance. Often, a simple RC filter on the ADS1224
analog inputs is all that is needed.
CLOCK INPUT (CLK)
This digital input supplies the system clock to the
ADS1224. The CLK frequency can be increased to
speed up the data rate. CLK must be left running during
normal operation. It may be turned off during Standby
mode to save power, but this is not required. The CLK
input may be driven with 5V logic, regardless of the
DVDD or AVDD voltage.
0
Minimize the overshoot and undershoot on CLK for the
best analog performance. A small resistor in series with
CLK (10Ω to 100Ω) can often help. CLK can be
generated from a number of sources including
standalone crystal oscillators and microcontrollers.
−
−
−
−
20
40
60
80
DATA READY/DATA OUTPUT (DRDY/DOUT)
This digital output pin serves two purposes. First, it
indicates when new data is ready by going LOW.
Afterwards, on the first rising edge of SCLK, the
DRDY/DOUT pin changes function and begins
outputting the conversion data, most significant bit
(MSB) first. Data is shifted out on each subsequent
SCLK rising edge. After all 24 bits have been retrieved,
−
100
0
31250
62500
Input Frequency (Hz)
Figure 20. Frequency Response
11
ꢇꢍ ꢚꢛ ꢀ ꢀ ꢁ
www.ti.com
SBAS286C − JUNE 2003 − REVISED JANUARY 2009
To help see the response at lower frequencies,
Figure 21 illustrates the response out to 1kHz. Notice
that signals at multiples of 120Hz are rejected. The
ADS1224 data rate and frequency response scale
0
20
40
60
80
−
−
−
−
directly with CLK frequency. For example, if f
CLK
increases from 2MHz to 4MHz, the data rate increases
from 120SPS to 240SPS, while the notches increase
from 120Hz to 240Hz.
0
−
100
30
40
50
60
70
80
−
−
−
−
20
40
60
80
Input Frequency (Hz)
Figure 22. Frequency Response Near 50Hz and
60Hz with f = 910kHz
CLK
SETTLING TIME
After changing the input multiplexer, selecting the input
buffer, or using temperature sensor, the first data is fully
settled. In the ADS1224, the digital filter is allowed to
settle after toggling any of the MUX0, MUX1, BUFEN,
or TEMPEN pins. Toggling of any of these digital pins
will cause the input to switch to the proper channel, start
conversions, and hold the DRDY/DOUT line high until
the digital filter is fully settled. For example, if MUX0
changes from low to high, selecting a different input
channel, DRDY/DOUT immediately goes high and the
conversion process restarts. DRDY/DOUT goes low
when fully settled data is ready for retrieval. There is no
need to discard any data. Figure 23 shows the timing of
the DRDY/DOUT line as the input multiplexer changes.
−
100
0
100 200 300 400 500 600 700 800 900 1k
Input Frequency (Hz)
Figure 21. Frequency Response to 1kHz
Rejecting 50Hz or 60Hz noise is as simple as choosing
the clock frequency. If simultaneous rejection of 50Hz
and 60Hz noise is desired, f
chosen. The data rate becomes 54.7sps and the
frequency response of the ADS1224 rejects the 50Hz
and 60Hz noise to below 60dB. The frequency
response of the ADS1224 near 50Hz and 60Hz with
= 910kHz can be
CLK
f
= 910kHz is shown in Figure 22.
CLK
MUX0
Abrupt change in internal VIN due to status change (for example, switch channels, temp sensor, buffer enable)
VIN
t1
ADS1224 holds DRDY/DOUT
Fully settled
data ready
until digital filter settles
DRDY/DOUT
DRDY/DOUT suppressed after status change
SYMBOL
(1)
DESCRIPTION
MIN
MAX
UNITS
t
Settling time (DRDY/DOUT held high) after a change in any of the
MUX0, MUX1, BUFEN, or TEMPEN pins
25.9
26.4
ms
1
(1)
Values given for f
CLK
= 2MHz. For different f frequencies, scale proportional to CLK period.
CLK
Figure 23. Example of Settling Time After Changing the Input Multiplexer
12
ꢇ ꢍꢚ ꢛꢀ ꢀꢁ
www.ti.com
SBAS286C − JUNE 2003 − REVISED JANUARY 2009
3
The ADS1224 uses a Sinc digital filter to improve noise
performance. Therefore, in certain instances, large
changes in input will require settling time. For example,
an external multiplexer in front of the ADS1224 can put
large changes in input voltage by simply switching input
channels. Abrupt changes in the input will require three
data cycles to settle. When continuously converting,
four readings may be necessary to settle the data. If the
change in input occurs in the middle of the first conver-
sion, three more full conversions of the fully settled input
will be required to get fully settled data. Discard the first
three readings because they will contain only partially−
settled data. Figure 24 illustrates the settling time for
the ADS1224 in Continuous Conversion mode.
Table 2. Ideal Output Code vs Input Signal
INPUT SIGNAL V
(AINP − AINN)
IN
(1)
IDEAL OUTPUT CODE
7FFFFFh
w +2VREF
+2VREF
223 * 1
000001h
000000h
FFFFFFh
0
−2VREF
223 * 1
223
800000h
ǒ
Ǔ
v −2VREF
223 * 1
(1)
Excludes effects of noise, INL, offset, and gain errors.
DATA RETRIEVAL
If the input is known to change abruptly, the mux can be
quickly switched to an alternate channel and quickly
switched back to the original channel. By toggling the
mux, the ADS1224 resets the digital filter and initiates a
new conversion. During this time, the DRDY/DOUT line
is held high until fully-settled data is available.
The ADS1224 continuously converts the analog input
signal. To retrieve data, wait until DRDY/DOUT goes
low, as shown in Figure 25. After this occurs, begin
shifting out the data by applying SCLKs. Data is shifted
out MSB first. It is not required to shift out all 24 bits of
data, but the data must be retrieved before the new data
DATA FORMAT
is updated (see t ) or else it will be overwritten. Avoid
2
data retrieval during the update period. DRDY/DOUT
remain at the state of the last bit shifted out until it is
The ADS1224 outputs 24 bits of data in binary two’s
complement format. The least significant bit (LSB) has
a weight of (2VREF)/(2 – 1). The positive full-scale
23
taken high (see t ), indicating that new data is being
6
updated. To avoid having DRDY/DOUT remain in the
state of the last bit, shift a 25th SCLK to force
DRDY/DOUT high (see Figure 26). This technique is
useful when a host controlling the ADS1224 is polling
DRDY/DOUT to determine when data is ready.
input produces an output code of 7FFFFFh and the
negative full-scale input produces an output code of
800000h. The output clips at these codes for signals
exceeding full-scale. Table 2 summarizes the ideal
output codes for different input signals.
Abrupt change in external VIN
VIN
Second Conversion; Third Conversion;
First Conversion;
Start of
VIN settled, but
digital filter
unsettled
VIN settled, but
digital filter
unsettled
Fourth Conversion;
VIN and digital filter
both settled
includes
conversion
unsettled VIN
DRDY/DOUT
Conversion
time
Figure 24. Settling Time in Continuous Conversion Mode
13
ꢇꢍ ꢚꢛ ꢀ ꢀ ꢁ
www.ti.com
SBAS286C − JUNE 2003 − REVISED JANUARY 2009
Data
Data Ready
New Data Ready
MSB
23
LSB
0
DRDY/DOUT
22
21
t4
t5
t2
t3
t6
1
24
SCLK
t3
t7
SYMBOL DESCRIPTION
MIN
MAX UNITS
t
t
DRDY/DOUT low to first SCLK rising edge
SCLK positive or negative pulse width
SCLK rising edge to new data bit valid: propogation delay
SCLK rising edge to old data bit valid: hold time
Data updating; no readback allowed
0
100
ns
ns
ns
ns
µs
ms
2
3
(1)
t
50
4
t
0
48
8.32
5
(1)
(1)
t
t
6
7
Conversion time (1/data rate)
8.32
(1)
Values given for f
CLK
= 2MHz. For different f frequencies, scale proportional to CLK period.
CLK
Figure 25. Data Retrieval Timing
Data
Data Ready
New Data Ready
DRDY/DOUT
SCLK
23
22
21
0
1
24
25
25th SCLK to Force DRDY/DOUT High
Figure 26. Data Retrieval with DRDY/DOUT Forced High Afterwards
14
ꢇ ꢍꢚ ꢛꢀ ꢀꢁ
www.ti.com
SBAS286C − JUNE 2003 − REVISED JANUARY 2009
SELF-CALIBRATION
STANDBY MODE
Self-calibration can be initiated at any time, although in
many applications the ADS1224 drift performance is so
good that the self-calibration performed automatically
at power-up is all that is needed. To initiate
self-calibration, apply at least two additional SCLKs
after retrieving 24 bits of data. Figure 27 shows the
timing pattern. The 25th SCLK will send DRDY/DOUT
high. The falling edge of the 26th SCLK will begin the
calibration cycle. Additional SCLK pulses may be sent
after the 26th SCLK; however, activity on SCLK should
be minimized during calibration for best results.
Standby
mode
dramatically
reduces
power
consumption (typically < 1µW with CLK stopped) by
shutting down all of the active circuitry. To enter Standby
mode, simply hold SCLK high after DRDY/DOUT goes
low, as shown in Figure 28. Standby mode can be
initiated at any time during readback; it is not necessary
to retrieve all 24 bits of data beforehand. Note that
during standby mode, the buffer must be disabled to
prevent loading of the inputs.
When t has passed with SCLK held high, Standby mode
11
will activate. DRDY/DOUT stays high when Standby
mode begins. SCLK must remain high to stay in Standby
mode. To exit Standby mode (wakeup), set SCLK low.
The first data after exiting Standby mode is valid. It is not
necessary to stop CLK during Standby mode, but doing
so will further reduce the digital supply current.
When the calibration is complete, DRDY/DOUT goes
low, indicating that new data is ready. There is no need
to alter the analog input signal applied to the ADS1224
during calibration; the input pins are disconnected
within the A/D converter and the appropriate signals are
applied internally and automatically. The first
conversion after a calibration is fully settled and valid for
use. The time required for a calibration depends on two
independent signals: the falling edge of SCLK and an
internal clock derived from CLK. Variations in the
internal calibration values will change the time required
Standby Mode With Self-Calibration
Self-calibration can be set to run immediately after
exiting Standby mode. This is useful when the
ADS1224 is put in Standby mode for long periods of
time and self-calibration is desired afterwards to
compensate for temperature or supply voltage
changes.
for calibration (t ) within the range given by the min/max
8
specs. t and t described in the next section are
11
12
affected likewise.
To force a self-calibration with Standby mode, shift 25
bits out before taking SCLK high to enter Standby
mode. Self-calibration then begins after wakeup.
Figure 29 shows the appropriate timing. Note the extra
time needed after wakeup for calibration before data is
ready. The first data after Standby mode with
self-calibration is fully settled and can be used.
Data Ready After Calibration
DRDY/DOUT
SCLK
23
22
21
0
23
Calibration Begins
1
24
25
26
t8
SYMBOL DESCRIPTION
(1)
MIN
MAX
UNITS
t
8
First data ready after calibration
77.1
77.9
ms
(1)
Values given for f = 2MHz. For different f
frequencies, scale proportional to CLK period.
CLK CLK
Figure 27. Self-Calibration Timing
15
ꢇꢍ ꢚꢛ ꢀ ꢀ ꢁ
www.ti.com
SBAS286C − JUNE 2003 − REVISED JANUARY 2009
Data Ready
Standby Mode
DRDY/DOUT
SCLK
23
22
21
0
23
Start Conversion
1
24
t9
t10
t11
SYMBOL DESCRIPTION
MIN
MAX
UNITS
(1)
(1)
t
SCLK high after DRDY/DOUT goes low to activate Standby mode
Standby mode activation time
0
8.272
8.304
28.1
ms
ms
ms
9
t
10
8.272
27.7
(1)
t
Data ready after exiting Standby mode
11
(2)
Values given for f
CLK
= 2MHz. For different f frequencies, scale proportional to CLK period.
CLK
Figure 28. Standby Mode Timing (can be used for single conversions)
Data Ready After Calibration
Standby Mode
DRDY/DOUT
SCLK
23
22
21
0
23
Begin Calibration
1
24
25
t10
t12
SYMBOL DESCRIPTION
(1)
MIN
MAX
UNITS
t
12
Data ready after exiting Standby mode and calibration
78.8
79.7
ms
(1)
Values given for f = 2MHz. For different f
frequencies, scale proportional to CLK period.
CLK CLK
Figure 29. Standby Mode with Self-Calibration Timing (can be used for single conversions)
high to stop the ADS1224 from converting and re-enter
Standby mode. Continue to hold SCLK high until ready
to start the next conversion. Operating in this fashion
greatly reduces power consumption since the
ADS1224 is shut down while idle between conversions.
Self-calibrations can be performed prior to the start of
the single conversions by using the waveform shown in
Figure 29.
SINGLE CONVERSIONS
When only single conversions are needed, Standby
mode can be used to start and stop the ADS1224. To
make a single conversion, first enter the Standby mode
holding SCLK high. Now, when ready to start the
conversion, take SCLK low. The ADS1224 wakes up
and begins the conversion. Wait for DRDY/DOUT to go
low, and then retrieve the data. Afterwards, take SCLK
16
ꢇ ꢍꢚ ꢛꢀ ꢀꢁ
www.ti.com
SBAS286C − JUNE 2003 − REVISED JANUARY 2009
Pay special attention to the reference and analog
inputs. These are the most critical circuits. Bypass the
voltage reference using similar techniques to the supply
voltages. The quality of the reference directly affects
the overall accuracy of the device. Make sure to use a
low noise and low drift reference such as the REF1004.
APPLICATIONS INFORMATION
GENERAL RECOMMENDATIONS
The ADS1224 is a high-resolution A/D converter.
Achieving optimal device performance requires careful
attention to the support circuitry and printed circuit
board (PCB) design. Figure 30 shows the basic
connections for the ADS1224. As with any precision
circuit, be sure to use good supply bypassing capacitor
techniques. A smaller value ceramic capacitor in
parallel with a larger value tantulum capacitor works
well. Place the capacitors, in particular the ceramic
ones, close to the supply pins. Use a ground plane and
tie the ADS1224 GND pin and bypass capacitors
directly to it. Avoid ringing on the digital inputs. Small
resistors (≈100Ω) in series with the digital pins can help
by controlling the trace impedance. Place these
resistors at the source end.
Often, only a simple RC filter is needed on the inputs.
This circuits limits the higher frequency noise. Avoid
low-grade dielectrics for the capacitors and place them
as close as possible to the input pins. Keep the traces
to the input pins short, and carefully watch how they are
routed on the PCB.
After the power supplies and reference voltage have
stabilized, issue a self-calibration command to
minimize offset and gain errors.
+5V
+5V
µ
µ
µ
µ
10 F
10 F
0.1 F
0.1 F
ADS1224
1
2
20
19
18
17
16
15
14
13
12
11
DVDD
SCLK
CLK
AVDD
VREFP
VREFN
GND
Ω
100
100
100
100
+2.5V Reference
Ω
Ω
Ω
100
100
100
µ
µ
10 F
0.1 F
3
Ω
Ω
Ω
4
DRDY/DOUT
MUX0
5
AINN1
AINP1
AINN2
AINP2
AINN3
AINP3
6
MUX1
7
TEMPEN
BUFEN
AINP4
Same as shown for AINP4 and AINN4.
8
9
10
220pF
Ω
301
AINN4
VINP
VINN
µ
0.1 F
Ω
301
220pF
Figure 30. Basic Connections
17
ꢇꢍ ꢚꢛ ꢀ ꢀ ꢁ
www.ti.com
SBAS286C − JUNE 2003 − REVISED JANUARY 2009
The falling edges of DRDY/DOUT, indicating that new
data is ready, will vary with respect to each other no
MULTICHANNEL SYSTEMS
Multiple ADS1224s can be operated in parallel to
measure multiple input signals. Figure 31 shows an
example of an eight-channel system. For simplicity, the
supplies and reference circuitry are not shown. The
same CLK signal should be applied to all devices. To
synchronize the ADS1224s, connect the same SCLK
signal to all devices. Then place all the devices in
Standby mode. Afterwards, starting a conversion will
synchronize all the ADS1224s; that is, they will sample
the input signals simultaneously. The DRDY/DOUT
outputs will go low at approximately the same time after
synchronization. When reading data from the devices,
the data appears in parallel on DRDY/DOUT as a result
of the common SCLK connection.
more than time t . This variation is due to possible
13
differences in the ADS1224 internal calibration settings.
To account for this, when using multiple devices, either
wait for t to pass after seeing one DRDY/DOUT go
13
low, or wait until all DRDY/DOUTs have gone low before
retrieving data.
Note that changing channels (using the MUX0 and
MUX1 pins), or using the input buffer (BUFEN) or the
temperature sensor (TEMPEN), may require more care
to settle the digital filter. For example, if the MUX0 pin
is toggled on one device and not the other, the
DRDY/DOUT line will be held high until the conversion
settles on the first device. The latter device will continue
conversions through this time. See the Settling Time
section of this data sheet for further details.
ADS1224
AINP1
AINN1
CLK
SCLK
Inputs
AINP4
AINN4
DRDY/DOUT
OUT1
MUX0
MUX1
MUX Select
OUT1
ADS1224
t13
AINP1
AINN1
CLK
SCLK
OUT2
Inputs
AINP4
AINN4
DRDY/DOUT
OUT2
MUX0
MUX1
MUX Select
CLK and SCLK
Sources
SYMBOL
(1)
DESCRIPTION
MIN
MAX
UNITS
t
Difference between DRDY/DOUTs going low in multichannel
systems
0.8
ms
13
(1)
Values given for f
CLK
= 2MHz. For different f frequencies, scale proportional to CLK period.
CLK
Figure 31. Example of Using Multiple ADS1224s in Parallel
18
ꢇ ꢍꢚ ꢛꢀ ꢀꢁ
www.ti.com
SBAS286C − JUNE 2003 − REVISED JANUARY 2009
a differential in/differential out amplifier with a gain of
VESSEL WEIGHING WITH FOUR LOAD
CELLS
499V/V (G = 1 + 2R /R ). Gain on the load cell gives
F
G
the amplifier a full-scale output of 5V.
In vessel weighing systems, four load cells are
frequently employed to measure the weight of the
vessel and its contents. The output of the load cells are
usually combined in an external summing junction box
that balances the load cells’ sensitivities for accuracy.
Each load cell input uses an external amplifier. The
outputs of the amplifiers connect to the analog inputs of
the ADS1224 through a low-pass filter. The cut-off
frequency is set to 360Hz, allowing full settling in a
single measurement cycle. A lower cut-off frequency
can be used to reduce noise from mechanical
vibrations, but at the expense of filter settling time.
The four differential inputs of the ADS1224 allow for
direct measurement of the four load cells individually. In
this way, the mechanical adjustments performed inside
the summing junction box are eliminated and are
replaced by digital summing of the load cells in
software. Figure 32 shows an example of such a
system.
The internal buffer of the ADS1224 is disabled, allowing
the VREFN pin to be grounded. Note that the loading
from the reference inputs will change the effective
reference voltage. The effective input impedance into
the VREFP and VREFN pins will lower the reference
voltage seen at these pins. At 2MHz, input impedance
is approximately 500kΩ. For the reference circuit shown
in Figure 32, this lowers the effective reference voltage
by approximately 0.1%.
The reference voltage of the ADS1224 is derived by
dividing down the AVDD supply voltage to 2.5V, while
the load cell has a positive full-scale output of 10mV. In
the figure, a low drift, dual op amp (OPA2335) provides
5V
+3V
µ
µ
µ
µ
0.1 F
0.1
F
0.1
F
1
F
RFI
Filter
(1)
Ω
1k
1k
AVDD
DVDD
DVCC
AVCC
VREFP
BUFEN
(1)
Ω
µ
0.1
F
5V
Ω
350
Shielded
Cable
TEMPEN
ADS1224
VREFN
Load Cell
1/2
Ω
100
2R
MSP430F41x
RFI
Filter
Ω
OPA2335
1k
1k
AINP1
AINN1
µ
0.22
F
Ω
(1)
R
F
F
G = 1 +
Ω
Ω
2.49k
R
G
AINP2
AINN2
AINP3
AINN3
AINP4
AINN4
CLK
P1.1/TA0/MCLK
P1.2/TA1
(1)
R
RFI
Filter
(1)
G
R
F
Ω
XIN
10
SCLK
2.49k
NOTE: (1) Low−drift resistors.
DRDY/DOUT
MUX0
P1.0/TA0
P1.6/CA0
P1.7/CA1
XOUT/TCLK
Ω
100
MUX1
RFI
Filter
1/2
GND
GND
OPA2335
Replicate for Channels 2, 3 and 4
Figure 32. Vessel Weighing System with Four Load Cells
19
ꢇꢍ ꢚꢛ ꢀ ꢀ ꢁ
www.ti.com
SBAS286C − JUNE 2003 − REVISED JANUARY 2009
SUMMARY OF SERIAL INTERFACE WAVEFORMS
DRDY/DOUT
SCLK
23
22
21
0
MSB
LSB
1
24
(a) Data Retrieval
DRDY/DOUT
SCLK
23
22
21
0
1
24
25
(b) Data Retrieval with DRDY/DOUT Forced High Afterwards
Data Ready
After Calibration
DRDY/DOUT
SCLK
23
22
21
0
Begin Calibration
26
1
24
25
(c) Self−Calibration
Data Ready
Standby Mode
23
22
21
0
DRDY/DOUT
SCLK
Start
Conversion
1
24
(d) Standby Mode/Single Conversions
Data Ready
After Calibration
Standby Mode
DRDY/DOUT
SCLK
23
22
21
0
Begin Calibration
1
24
25
(e) Standby Mode/Single Conversions with Self−Calibration
Figure 33. Summary of Serial Interface Waveforms
20
ꢇ ꢍꢚ ꢛꢀ ꢀꢁ
www.ti.com
SBAS286C − JUNE 2003 − REVISED JANUARY 2009
Revision History
DATE
REV
PAGE
SECTION
Analog Input
DESCRIPTION
9
Measurement with the
Input Buffer
Added last sentence to first paragraph describing standby mode.
Added last sentence to first paragraph describing standby mode.
12/2/08
C
15
Standby Mode
:
NOTE Page numbers for previous revisions may differ from page numbers in the current version.
21
PACKAGE OPTION ADDENDUM
www.ti.com
25-Nov-2008
PACKAGING INFORMATION
Orderable Device
ADS1224IPWR
Status (1)
ACTIVE
ACTIVE
ACTIVE
ACTIVE
Package Package
Pins Package Eco Plan (2) Lead/Ball Finish MSL Peak Temp (3)
Qty
Type
Drawing
TSSOP
PW
20
20
20
20
2000 Green (RoHS & CU NIPDAU Level-2-260C-1 YEAR
no Sb/Br)
ADS1224IPWRG4
ADS1224IPWT
TSSOP
TSSOP
TSSOP
PW
PW
PW
2000 Green (RoHS & CU NIPDAU Level-2-260C-1 YEAR
no Sb/Br)
250 Green (RoHS & CU NIPDAU Level-2-260C-1 YEAR
no Sb/Br)
ADS1224IPWTG4
250 Green (RoHS & CU NIPDAU Level-2-260C-1 YEAR
no Sb/Br)
(1) The marketing status values are defined as follows:
ACTIVE: Product device recommended for new designs.
LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.
NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in
a new design.
PREVIEW: Device has been announced but is not in production. Samples may or may not be available.
OBSOLETE: TI has discontinued the production of the device.
(2)
Eco Plan - The planned eco-friendly classification: Pb-Free (RoHS), Pb-Free (RoHS Exempt), or Green (RoHS & no Sb/Br) - please check
http://www.ti.com/productcontent for the latest availability information and additional product content details.
TBD: The Pb-Free/Green conversion plan has not been defined.
Pb-Free (RoHS): TI's terms "Lead-Free" or "Pb-Free" mean semiconductor products that are compatible with the current RoHS requirements
for all 6 substances, including the requirement that lead not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered
at high temperatures, TI Pb-Free products are suitable for use in specified lead-free processes.
Pb-Free (RoHS Exempt): This component has a RoHS exemption for either 1) lead-based flip-chip solder bumps used between the die and
package, or 2) lead-based die adhesive used between the die and leadframe. The component is otherwise considered Pb-Free (RoHS
compatible) as defined above.
Green (RoHS & no Sb/Br): TI defines "Green" to mean Pb-Free (RoHS compatible), and free of Bromine (Br) and Antimony (Sb) based flame
retardants (Br or Sb do not exceed 0.1% by weight in homogeneous material)
(3)
MSL, Peak Temp. -- The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder
temperature.
Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is
provided. TI bases its knowledge and belief on information provided by third parties, and makes no representation or warranty as to the
accuracy of such information. Efforts are underway to better integrate information from third parties. TI has taken and continues to take
reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on
incoming materials and chemicals. TI and TI suppliers consider certain information to be proprietary, and thus CAS numbers and other limited
information may not be available for release.
In no event shall TI's liability arising out of such information exceed the total purchase price of the TI part(s) at issue in this document sold by TI
to Customer on an annual basis.
Addendum-Page 1
PACKAGE MATERIALS INFORMATION
www.ti.com
30-Jan-2009
TAPE AND REEL INFORMATION
*All dimensions are nominal
Device
Package Package Pins
Type Drawing
SPQ
Reel
Reel
A0 (mm)
B0 (mm)
K0 (mm)
P1
W
Pin1
Diameter Width
(mm) W1 (mm)
(mm) (mm) Quadrant
ADS1224IPWR
ADS1224IPWT
TSSOP
TSSOP
PW
PW
20
20
2000
250
330.0
180.0
16.4
16.4
6.95
6.95
7.1
7.1
1.6
1.6
8.0
8.0
16.0
16.0
Q1
Q1
Pack Materials-Page 1
PACKAGE MATERIALS INFORMATION
www.ti.com
30-Jan-2009
*All dimensions are nominal
Device
Package Type Package Drawing Pins
SPQ
Length (mm) Width (mm) Height (mm)
ADS1224IPWR
ADS1224IPWT
TSSOP
TSSOP
PW
PW
20
20
2000
250
346.0
190.5
346.0
212.7
33.0
31.8
Pack Materials-Page 2
MECHANICAL DATA
MTSS001C – JANUARY 1995 – REVISED FEBRUARY 1999
PW (R-PDSO-G**)
PLASTIC SMALL-OUTLINE PACKAGE
14 PINS SHOWN
0,30
0,19
M
0,10
0,65
14
8
0,15 NOM
4,50
4,30
6,60
6,20
Gage Plane
0,25
1
7
0°–8°
A
0,75
0,50
Seating Plane
0,10
0,15
0,05
1,20 MAX
PINS **
8
14
16
20
24
28
DIM
3,10
2,90
5,10
4,90
5,10
4,90
6,60
6,40
7,90
9,80
9,60
A MAX
A MIN
7,70
4040064/F 01/97
NOTES: A. All linear dimensions are in millimeters.
B. This drawing is subject to change without notice.
C. Body dimensions do not include mold flash or protrusion not to exceed 0,15.
D. Falls within JEDEC MO-153
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
PACKAGE OPTION ADDENDUM
www.ti.com
11-Apr-2013
PACKAGING INFORMATION
Orderable Device
ADS1224IPWR
Status Package Type Package Pins Package
Eco Plan Lead/Ball Finish
MSL Peak Temp
Op Temp (°C)
-40 to 85
Top-Side Markings
Samples
Drawing
Qty
(1)
(2)
(3)
(4)
ACTIVE
TSSOP
TSSOP
TSSOP
TSSOP
PW
20
20
20
20
2000
Green (RoHS
& no Sb/Br)
CU NIPDAU
CU NIPDAU
CU NIPDAU
CU NIPDAU
Level-2-260C-1 YEAR
Level-2-260C-1 YEAR
Level-2-260C-1 YEAR
Level-2-260C-1 YEAR
ADS1224
ADS1224IPWRG4
ADS1224IPWT
ACTIVE
ACTIVE
ACTIVE
PW
PW
PW
2000
250
Green (RoHS
& no Sb/Br)
-40 to 85
ADS1224
ADS1224
ADS1224
Green (RoHS
& no Sb/Br)
-40 to 85
ADS1224IPWTG4
250
Green (RoHS
& no Sb/Br)
-40 to 85
(1) The marketing status values are defined as follows:
ACTIVE: Product device recommended for new designs.
LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.
NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design.
PREVIEW: Device has been announced but is not in production. Samples may or may not be available.
OBSOLETE: TI has discontinued the production of the device.
(2) Eco Plan - The planned eco-friendly classification: Pb-Free (RoHS), Pb-Free (RoHS Exempt), or Green (RoHS & no Sb/Br) - please check http://www.ti.com/productcontent for the latest availability
information and additional product content details.
TBD: The Pb-Free/Green conversion plan has not been defined.
Pb-Free (RoHS): TI's terms "Lead-Free" or "Pb-Free" mean semiconductor products that are compatible with the current RoHS requirements for all 6 substances, including the requirement that
lead not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, TI Pb-Free products are suitable for use in specified lead-free processes.
Pb-Free (RoHS Exempt): This component has a RoHS exemption for either 1) lead-based flip-chip solder bumps used between the die and package, or 2) lead-based die adhesive used between
the die and leadframe. The component is otherwise considered Pb-Free (RoHS compatible) as defined above.
Green (RoHS & no Sb/Br): TI defines "Green" to mean Pb-Free (RoHS compatible), and free of Bromine (Br) and Antimony (Sb) based flame retardants (Br or Sb do not exceed 0.1% by weight
in homogeneous material)
(3) MSL, Peak Temp. -- The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder temperature.
(4)
Multiple Top-Side Markings will be inside parentheses. Only one Top-Side Marking contained in parentheses and separated by a "~" will appear on a device. If a line is indented then it is a
continuation of the previous line and the two combined represent the entire Top-Side Marking for that device.
Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is provided. TI bases its knowledge and belief on information
provided by third parties, and makes no representation or warranty as to the accuracy of such information. Efforts are underway to better integrate information from third parties. TI has taken and
continues to take reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on incoming materials and chemicals.
TI and TI suppliers consider certain information to be proprietary, and thus CAS numbers and other limited information may not be available for release.
In no event shall TI's liability arising out of such information exceed the total purchase price of the TI part(s) at issue in this document sold by TI to Customer on an annual basis.
Addendum-Page 1
PACKAGE OPTION ADDENDUM
www.ti.com
11-Apr-2013
Addendum-Page 2
PACKAGE MATERIALS INFORMATION
www.ti.com
26-Jan-2013
TAPE AND REEL INFORMATION
*All dimensions are nominal
Device
Package Package Pins
Type Drawing
SPQ
Reel
Reel
A0
B0
K0
P1
W
Pin1
Diameter Width (mm) (mm) (mm) (mm) (mm) Quadrant
(mm) W1 (mm)
ADS1224IPWR
ADS1224IPWT
TSSOP
TSSOP
PW
PW
20
20
2000
250
330.0
180.0
16.4
16.4
6.95
6.95
7.1
7.1
1.6
1.6
8.0
8.0
16.0
16.0
Q1
Q1
Pack Materials-Page 1
PACKAGE MATERIALS INFORMATION
www.ti.com
26-Jan-2013
*All dimensions are nominal
Device
Package Type Package Drawing Pins
SPQ
Length (mm) Width (mm) Height (mm)
ADS1224IPWR
ADS1224IPWT
TSSOP
TSSOP
PW
PW
20
20
2000
250
367.0
210.0
367.0
185.0
38.0
35.0
Pack Materials-Page 2
IMPORTANT NOTICE
Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, enhancements, improvements and other
changes to its semiconductor products and services per JESD46, latest issue, and to discontinue any product or service per JESD48, latest
issue. Buyers should obtain the latest relevant information before placing orders and should verify that such information is current and
complete. All semiconductor products (also referred to herein as “components”) are sold subject to TI’s terms and conditions of sale
supplied at the time of order acknowledgment.
TI warrants performance of its components to the specifications applicable at the time of sale, in accordance with the warranty in TI’s terms
and conditions of sale of semiconductor products. Testing and other quality control techniques are used to the extent TI deems necessary
to support this warranty. Except where mandated by applicable law, testing of all parameters of each component is not necessarily
performed.
TI assumes no liability for applications assistance or the design of Buyers’ products. Buyers are responsible for their products and
applications using TI components. To minimize the risks associated with Buyers’ products and applications, Buyers should provide
adequate design and operating safeguards.
TI does not warrant or represent that any license, either express or implied, is granted under any patent right, copyright, mask work right, or
other intellectual property right relating to any combination, machine, or process in which TI components or services are used. Information
published by TI regarding third-party products or services does not constitute a license to use such products or services or a warranty or
endorsement thereof. Use of such information may require a license from a third party under the patents or other intellectual property of the
third party, or a license from TI under the patents or other intellectual property of TI.
Reproduction of significant portions of TI information in TI data books or data sheets is permissible only if reproduction is without alteration
and is accompanied by all associated warranties, conditions, limitations, and notices. TI is not responsible or liable for such altered
documentation. Information of third parties may be subject to additional restrictions.
Resale of TI components or services with statements different from or beyond the parameters stated by TI for that component or service
voids all express and any implied warranties for the associated TI component or service and is an unfair and deceptive business practice.
TI is not responsible or liable for any such statements.
Buyer acknowledges and agrees that it is solely responsible for compliance with all legal, regulatory and safety-related requirements
concerning its products, and any use of TI components in its applications, notwithstanding any applications-related information or support
that may be provided by TI. Buyer represents and agrees that it has all the necessary expertise to create and implement safeguards which
anticipate dangerous consequences of failures, monitor failures and their consequences, lessen the likelihood of failures that might cause
harm and take appropriate remedial actions. Buyer will fully indemnify TI and its representatives against any damages arising out of the use
of any TI components in safety-critical applications.
In some cases, TI components may be promoted specifically to facilitate safety-related applications. With such components, TI’s goal is to
help enable customers to design and create their own end-product solutions that meet applicable functional safety standards and
requirements. Nonetheless, such components are subject to these terms.
No TI components are authorized for use in FDA Class III (or similar life-critical medical equipment) unless authorized officers of the parties
have executed a special agreement specifically governing such use.
Only those TI components which TI has specifically designated as military grade or “enhanced plastic” are designed and intended for use in
military/aerospace applications or environments. Buyer acknowledges and agrees that any military or aerospace use of TI components
which have not been so designated is solely at the Buyer's risk, and that Buyer is solely responsible for compliance with all legal and
regulatory requirements in connection with such use.
TI has specifically designated certain components as meeting ISO/TS16949 requirements, mainly for automotive use. In any case of use of
non-designated products, TI will not be responsible for any failure to meet ISO/TS16949.
Products
Applications
Audio
www.ti.com/audio
amplifier.ti.com
dataconverter.ti.com
www.dlp.com
Automotive and Transportation www.ti.com/automotive
Communications and Telecom www.ti.com/communications
Amplifiers
Data Converters
DLP® Products
DSP
Computers and Peripherals
Consumer Electronics
Energy and Lighting
Industrial
www.ti.com/computers
www.ti.com/consumer-apps
www.ti.com/energy
dsp.ti.com
Clocks and Timers
Interface
www.ti.com/clocks
interface.ti.com
logic.ti.com
www.ti.com/industrial
www.ti.com/medical
Medical
Logic
Security
www.ti.com/security
Power Mgmt
Microcontrollers
RFID
power.ti.com
Space, Avionics and Defense
Video and Imaging
www.ti.com/space-avionics-defense
www.ti.com/video
microcontroller.ti.com
www.ti-rfid.com
www.ti.com/omap
OMAP Applications Processors
Wireless Connectivity
TI E2E Community
e2e.ti.com
www.ti.com/wirelessconnectivity
Mailing Address: Texas Instruments, Post Office Box 655303, Dallas, Texas 75265
Copyright © 2013, Texas Instruments Incorporated
相关型号：
©2020 ICPDF网 联系我们和版权申明