Figure 31. Simplified diagram when Vicm < 40% VCC

+

-

D

D

D

+

-

GND

OUT

VIN+

Vcc

Vicm<40%Vcc

+2.7V to +18V

Load

R1

R1

R2

A2

A1

A3

VIN-

Reference

voltage 0.6V

CMPOUT

CMPIN

RESET

+

-

Ir

Ir

Ir

Ir

ILoad

Vsense

12.5kΩ

5kΩ

V2

When the input common-mode voltage is lower than 40% of the Vcc, this time the amplifier A1 is active. A Iload

current flowing into the shunt generates Vsense, a small differential voltage between input pins of the TSC20x.

Due to the A1 amplifier, a current Ir, equal to Vsense/5kΩ, flows through the input pin IN-. This Ir current is

recopied from a precision current mirror whose output is directed into R2, converting the signal back into a voltage

V2 as described by equation 1, and then amplified by the A3 amplifier as described by equation 2.

The input bias current of IN- is composed of the supply current of the input stage (roughly 30 µA), as well as the

Ir. The value of Ir is directly linked to the sensing voltage Vsense.

Figure 32 shows the sum of bias current into the input pins.

Figure 32. Input bias current vs. Vsense for a Vicm = -16 V

0

100

200

300

400

500

600

0

100

200

300

400

500

600

-200

-150

-100

-50

0

-200

-150

-100

-50

0

Iibp

Vcc=12V

Vicm=-16V

T=25°C

Iibn

Vsense (mV)

In mode 2 the accuracy might be slightly lower than in mode 1 as described by Figure 9. That difference is

principally due to the current Ir recopy.

TSC200, TSC201, TSC202

Theory of operation

DS13882 - Rev 2

page 14/34