TSC2012 datasheet(24/50 Pages) STMICROELECTRONICS

24 / 50 page

So due to the architecture of the TSC2011, the current to be measured must be much larger than the input bias

current. In case of small current to measure the Iib current must be taken into account.

Figure 55. Input bias current vs. common mode voltage Vcc = 5 V

-20

-10

-600

-500

-400

-300

-200

-100

100

200

300

400

500

600

Iibp

Vref=Vcc/2

Vsense=0V

Vcc=5V

Iibn

Vicm (V)

•

Gnd < Vicm < Vcc

In this manner, the TSC2011 is only powered by the power supply Vcc, and the iib currents are very close to 0 µA

and do not have any impact on the current measurement.

•

- 20 V < Vicm < Gnd

The TSC2011 is fully functional in this range of common mode voltage and has also been characterized.

As the high positive common mode voltage, in this specific range, the TSC2011 is also powered by the input, see

Figure 56. Power supply when Vicm < Gnd.

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.

TSC2010, TSC2011, TSC2012

Application information

DS13057 - Rev 7

page 24/50

TSC2012 Fiches technique(PDF) 24 Page - STMicroelectronics