TSC2012 datasheet(25/54 Pages) STMICROELECTRONICS

25 / 54 page

In Figure 55. Input bias current vs. common mode voltage Vcc = 5 V, the current used to power the TSC2011

increases together with the Vicm voltage. The slope represents the internal common mode resistances. The most

part of the current is drawn by 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 around 450 µA. Some of it being Vicm / (R4+R1) and some supplies the

input stage of the circuit, roughly 250 µA. On the In- pin 250 µA is drawn only.

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.

TSC2010, TSC2011, TSC2012

Theory of operation

DS13057 - Rev 4

page 25/54

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