TSZ182 datasheet(32/39 Pages) STMICROELECTRONICS

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Application information

TSZ182

32/39

DocID029836 Rev 1

5.14.3

Low-side current sensing

Power management mechanisms are found in most electronic systems. Current sensing is

useful for protecting applications. The low-side current sensing method consists of placing

a sense resistor between the load and the circuit ground. The resulting voltage drop is

amplified using the TSZ182 (see Figure 64: "Low-side current sensing schematic").

Figure 64: Low-side current sensing schematic

Vout can be expressed as follows:

Equation 3

Assuming that Rf2 = Rf1 = Rf and Rg2 = Rg1 = Rg, Equation 3 can be simplified as follows:

Equation 4

The main advantage of using the chopper of the TSZ182 for a low-side current sensing,

is that the errors due to Vio and Iio are extremely low and may be neglected.

Therefore, for the same accuracy, the shunt resistor can be chosen with a lower value,

resulting in lower power dissipation, lower drop in the ground path, and lower cost.

Particular attention must be paid to the matching and precision of Rg1, Rg2, Rf1, and Rf2,

to maximize the accuracy of the measurement.

Rshunt

Rg 1

Rg 2

Rf1

5 V

Vout

Rf2

T SZ182

ou t

shun t

I 1

–

io 1

–

out

shunt

io 1

–

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