RS
V+
4
3
4
3
+5V
+5V
+5V
REFOUT BUFIN
BUFOUT
5
5
REF
BUF
Digital
I/O
INA139
INA139
12-Bit
A/D
2
2
1
1
MUX
PGIA
Converter
R
25kΩ
L
R
25kΩ
L
Clock
Divider
Oscillator
Serial
I/O
ADS7870
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.
FIGURE 6. Bipolar Current Measurement Using a Differential Input of the A/D Converter.
Other INA169s
Digital I/O on the ADS7870 provides power to
select the desired INA169. Diodes prevent
output current of an on INA169 from flowing
into an off INA169.
INA169
V+
+5V
––
REFOUT BUFIN
BUFOUT
REF
BUF
Digital
I/O
INA169
V+
––
12-Bit
A/D
MUX
PGIA
Converter
1N4148
Clock
Divider
Oscillator
Serial
I/O
RL
ADS7870
FIGURE 7. Multiplexed Measurement Using Logic Signal for Power.
INA139, INA169
8
SBOS181D
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