LOAD

V Supply

load

Current

+

VOUT

Vcc

R1

R3

+

Vshunt

R4

+

Vcc

R2

Vcc

LPV821

R5

R6

Vbias

LPV821

To ADC REF

input

15

LPV821

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SNOSD36A – AUGUST 2017 – REVISED DECEMBER 2017

Product Folder Links: LPV821

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Copyright © 2017, Texas Instruments Incorporated

9 Application and Implementation

NOTE

Information in the following applications sections is not part of the TI component

specification, and TI does not warrant its accuracy or completeness. TI’s customers are

responsible for determining suitability of components for their purposes. Customers should

validate and test their design implementation to confirm system functionality.

9.1 Application Information

The LPV821 is a unity-gain stable, precision operational amplifier with very low offset voltage drift; the device is

also free from output phase reversal. Applications with noisy or high-impedance power supplies require

decoupling capacitors close to the device power-supply pins. In most cases, 0.1-μF capacitors are adequate.

9.2 Typical Applications

9.2.1

Low-Side Current Measurement

This single-supply, low-side, current-sensing solution shown in Figure 40 detects load currents up to 1 A. This

design uses the LPV821 because of its low offset voltage and rail-to-rail input and output. The LPV821 in the

main signal path is configured as a difference amplifier and a second LPV821 provides a buffered bias voltage to

allow transition of signal below and above the bias level for bi-direction current sensing. The low offset voltage

and offset drift of the LPV821 facilitate excellent dc accuracy for the circuit.

Figure 40. Low-Side Current Measurement

9.2.1.1 Design Requirements

The design requirements are as follows:

•

Supply Voltage: 3.3 V DC

•

Input: 1 A (Max)

•

Output: 1.65V ± 1.54 V ; (110 mV to 3.19 V)