OUT

LMP8272

+

-

A1

GND

+IN

-IN

A2

GAIN = 2

A1

A2

100 k:

GAIN = 7

C1

PROPRIETARY

LEVEL-SHIFT

CIRCUITRY

I

OUT

LMP8272

+

-

A1

GND

+IN

-IN

A2

GAIN = 2

A1

A2

100 k:

GAIN = 7

C1

I

PROPRIETARY

LEVEL-SHIFT

CIRCUITRY

OBSOLETE

LMP8272

www.ti.com

SNOSAP7F – AUGUST 2005 – REVISED APRIL 2013

The LMP8272 can be used for high side current sensing. The large common mode voltage range of this device

allows it to sense signals outside of its supply voltage range. Also, the LMP8272 has very high CMRR, which

enables it to sense very small signals in presence of larger common mode signals. The system in Figure 26

detected and amplified by LMP8272 in the presence of a common mode signal of up to 16V with highest

accuracy.

Figure 26. High Side Current Sensing

LOW SIDE CURRENT SENSING

Low side current measurements can cause a problem for operational amplifiers by exceeding the negative

common mode voltage limit of the device. In Figure 27, the load current is returning to the power source through

a common connection that has a parasitic resistance. The voltage drop across the parasitic resistances can

cause the ground connection of the measurement circuits to be at a positive voltage with respect to the common

side of the sense resistor. This will result in one or both of the inputs being negative with respect to the circuit’s

ground. The LMP8272 has a wide extended input common mode voltage range of

−2V to 16V and will function in

this condition.

Figure 27. Low Side Current Sensing

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