February 2014

DocID025330 Rev 1

1/14

www.st.com

AN4366

Application note

Compensate the input offset of a high-side current sensing

Nicolas Aupetit

Introduction

This application note explains how to configure a high-side current sensing when it is powered in single

supply. This approach is especially useful when a low current must be measured.

A high-side current sensing can amplify input differential signals at a common-mode voltage well

beyond the power supply rail. This common-mode voltage, in a current-sense amplifier such as the

TSC101, can rise to 28 V and can rise even higher in the TSC103. The device amplifies small voltages

across a shunt resistor on the high-voltage rail and feeds it to a low-voltage ADC generally embedded

into a microcontroller (see Figure 1). By construction, all current sensing devices have a small input

offset. Depending on whether this input offset voltage is positive or negative, there may be an impact on

the measurement of a low current.

Figure 1: Typical application schematic

Load

Rin1

Rin2

Vcc

Rg

Microcontroller

Rshunt

Rin1

Rin2

Rg

+

-

+

-