TSC1031 datasheet(19/26 Pages) STMICROELECTRONICS

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TSC1031

Application information

Doc ID 16875 Rev 2

19/26

Application information

The TSC1031 can be used to measure current and to feed back the information to a

microcontroller.

Figure 22.

Typical application

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 exactly matches 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 is multiplied by a ratio K2 and the resulting current flows into resistor

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

VRg3 =Rg3.K2.IRg1 =(Rg3/Rg1).K2.Vsense=K1.K2.Vsense with K1=Rg3/Rg1=10.

The voltage across the Rg3 resistor is buffered to the Out pin by the voltage buffer, featuring

a gain equal to 2. Therefore Vout can be expressed as:

Vout = 2.K1.K2.Vsense = Av .Vsense with Av= 2.K1.K2

or: Vout = Av .Rsense.Iload

Common-mode voltage: 2.9 V to 70 V

AM06157

5 V

Vsense

Vout

Iload

Rsense

Out

Rg1

Rg2

Current

multiplier

Sense

amplifier

Vcc+

TSC1031

Vcc-

2.5 or 5

µController

ADC

Vcc

Gnd

SEL

GPIO

Rg3

50K

Rf2

Rf1

Rf3

Gnd

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