AN4366 Datasheet, PDF (1/14 Pages) STMicroelectronics – Compensate the input offset of a high-side current sensing

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
Rshunt
Load
Rin1
Rin2
Vcc
+
-
+
Rg
-
Microcontroller
February 2014
DocID025330 Rev 1
1/14
www.st.com