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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
