October 2013

DocID024731 Rev 1

1/20

www.st.com

AN4304

Application note

How to filter the input of a high-side current sensing

Nicolas Aupetit

Introduction

This application note explains how to filter the input signal of a current sensing. The approach is

especially useful for applications where the RF constraint is very important.

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. In the TSC103, it can go even higher. The device amplifies small voltages across a shunt

resistor on the high-voltage rail and feeds it to a low-voltage ADC which is generally embedded into a

microcontroller (Figure 1: "Typical application schematic"). In many applications, the current-sense

signal frequently needs to be filtered at the source, ie, across the sense resistor.

Figure 1: Typical application schematic