Datasheet
13
®
INA125
INPUT PROTECTION
The inputs of the INA125 are individually protected for
voltage up to ±40V. For example, a condition of –40V on
one input and +40V on the other input will not cause
damage. Internal circuitry on each input provides low series
impedance under normal signal conditions. To provide
equivalent protection, series input resistors would contribute
FIGURE 6. Psuedoground Bridge Measurement, 5V Single Supply.
excessive noise. If the input is overloaded, the protection
circuitry limits the input current to a safe value of approxi-
mately 120µA to 190µA. The typical performance curve
“Input Bias Current vs Input Overload Voltage” shows this
input current limit behavior. The inputs are protected even if
the power supplies are disconnected or turned off.
A
1
Ref
Amp
2.5V
A
2
30kΩ
10kΩ
10kΩ
30kΩ
Bandgap
V
REF
13
12
14
15
16
4
6
9
10
11
IA
REF
5
2.5V
(1)
(Psuedoground)
8
7
R
G
Load
Sense
INA125
V
REF
COM
V
REF
BG
V
REF
2.5
V
REF
5
V
REF
10
V
IN
+
V
IN
–
1
3
+5V
2
SLEEP
+
–
V
O
= +2.5V +
[
(
V
IN
– V
IN
)
(
4 +
)
]
+–
60kΩ
R
G
NOTE: (1) “Psuedoground” is at +2.5V above actual ground.
This provides a precision reference voltage for succeeding
single-supply op amp stages.