TSC2012 datasheet(26/54 Pages) STMICROELECTRONICS

26 / 54 page

Figure 56. Power supply when Vicm < Gnd

Most part of the current is still due to the pin In+ as we can see on the iibp curve of Figure 9. Input bias current vs.

temperature with VCC = 5 V. The current is about - 300 µA, some of it being Vicm / (R4 + R1) and some other

supplies the circuit, roughly 250 µA. A small part of the current, coming from the common mode rail, is also due to

the input In– in order to power the TSC2011, in a range of - 100 µV.

•

Output common mode range

The TSC2011 output common mode voltage level can be set thanks to voltages applied on the Vref1 and Vref2

pins. These two pins allow the device to be set either in bidirectional or in unidirectional operation. The voltage

applied to those pins must not exceed the Vcc range. The different configurations are detailed in the section

Unidirectionnal/Bidirectionnal operation.

As depicted by the Figure 57. Vref powered by an external voltage source, Vref1 and Vref2 pins can be driven by

an external voltage source capable of sourcing/sinking a current following the equation below:

Iref= Vicm−Vref

5kΩ+275kΩ+25kΩ

(1)

Figure 57. Vref powered by an external voltage source

TSC2010, TSC2011, TSC2012

Theory of operation

DS13057 - Rev 4

page 26/54

TSC2012 数据表(PDF) 26 Page - STMicroelectronics