INA138_15 Datasheet, PDF (16/27 Pages) Texas Instruments – INA1x8 High-Side Measurement Current Shunt Monitor

INA138, INA168
SBOS122D – DECEMBER 1999 – REVISED DECEMBER 2014
Typical Applications (continued)
Load Current
Output
Sign
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Time
Figure 16. Bipolar Current Measurements Results (arbitrary scale)
8.2.5 Bipolar Current Measurement Using Differential Input of A/D Converter
The INA138 or INA168 devices can be used with an A/D Converter such as the ADS7870 programmed for
differential mode operation. Figure 17 illustrates this configuration. In this configuration the use of two INA's
allows for bi-directional current measurement. Depending upon the polarity of the current, one of the INA's will
provide an output voltage while the other output is zero. In this way the A/D converter will read the polarity of
current directly, without the need for additional circuitry.
V+
R_S
+5V
5
4
3
3
4
+5V
5
+5V
Digital
I/O
REF_OUT BUF_IN
BUF_OUT
REF
BUF
INA138
INA138
1
2
2
1
MUX
PGIA
12-Bit A/D
Converter
RL
25kΩ
RL
25kΩ
A/D converter programmed for differential input.
Depending on polarity of current, one INA138 provides
an output voltage, the output of the other is zero.
Clock
Divider
Oscillator
ADS7870
Serial
I/O
Figure 17. Bipolar Current Measurement Using Differential Input of A/D Converter
16
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