TSC103IDT datasheet(16/23 Pages) STMICROELECTRONICS

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Application information

TSC103

16/23

Doc ID 16873 Rev 1

Application information

The TSC103 can be used to measure current and to feed back the information to a

microcontroller.

Figure 9.

Single-supply configuration 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’s 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 adjusts

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

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

Since the voltage across the Rg3 resistor is buffered to the Out pin, Vout can be expressed

as:

Vout =(Rg3/Rg1).Vsense

or:

Vout =(Rg3/Rg1).Rsense.Iload

5 V

Vsense

Vout

Iload

Rsense

µ Controller

ADC

Gnd

Vcc

GPIO1

GPIO2

Vcc+

TSC103

Out

Gnd

SEL1

SEL2

Vcc-

Common-mode voltage: 2.9 V to 70 V

AM04517

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