REF

Serial

I/O

ADS7870

Clock

Divider

Oscillator

BUF

OUT

BUF

IN

REF

OUT

12-Bit

A/D

Converter

BUF

MUX

Digital

I/O

PGIA

5 V

1

2

5 V

5

4

3

1

2

5 V

5

4

3

R

S

RL

25 k

RL

25 k

V+

INA139

INA139

The A/D converter is programmed for differential input.

Depending on the polarity of the current, one INA139 provides

an output voltage whereas the output of the other is zero.

Ω

Ω

Copyright © 2017, Texas Instruments Incorporated

Time

Load Current

Output

Sign

17

INA139, INA169

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SBOS181F – DECEMBER 2000 – REVISED FEBRUARY 2017

Product Folder Links: INA139 INA169

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Copyright © 2000–2017, Texas Instruments Incorporated

Typical Applications (continued)

8.2.4.1 Application Curve

Figure 16. Bipolar Current Measurement Results (Arbitrary Scale)

8.2.5 Bipolar Current Measurement Using a Differential Input of the A/D Converter

The INA139 or INA169 devices can be used with an ADC such as the ADS7870 programmed for differential

mode operation. Figure 17 illustrates this configuration. In this configuration, the use of two devices allows for

bidirectional current measurement. Depending upon the polarity of the current, one of the devices provides an

output voltage while the other output is zero. In this way, the ADC reads the polarity of current directly, without

requiring additional circuitry.

Figure 17. Bipolar Current Measurement Using a Differential Input of the A/D Converter