TSC101AIYLT datasheet(13/18 Pages) STMICROELECTRONICS

13 / 18 page

TSC101

Application information

13/18

Application information

TSC101 can be used to measure current and to feed back the information to a micro

controller, as shown in Figure 6 below.

Figure 6.

Typical application schematic

The current from the supply flows to the load through the Rsense resistor causing a voltage

drop equal to Vsense across Rsense. The amplifier input currents are negligible, therefore its

inverting input voltage is equal to Vm. The amplifier's open-loop gain forces its non-inverting

input to the same voltage as the inverting input. As a consequence, the amplifier will adjust

current flowing through Rg1 so that the voltage drop across Rg1 will exactly match Vsense.

Therefore, the drop across Rg1 is:

VRg1=Vsense=Rsense.Iload

If IRg1 is the current flowing through Rg1, then IRg1 is given by the formula:

IRg1=Vsense/Rg1

The IRg1 current flows entirely into resistor Rg3 (the input bias current of the buffer is

negligible). Therefore, the voltage drop on the Rg3 resistor can be calculated as follows:

VRg3=Rg3.IRg1=(Rg3/Rg1).Vsense

Vsense

Vout

load

Iload

2.8V to 30V

Rsense

Vreg

Out

GND

VCC

Rg1Rg2

Rg3

TSC101

Microcontroller

ADC

GND

VCC

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