TSB7191 datasheet(23/34 Pages) STMICROELECTRONICS

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Typical applications

6.1

Low-side current sensing

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

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 TSB7191 and the TSB7192 (see the following

figure).

Figure 46. Low-side current sensing schematic

Rshunt

Rg1

Rg2

Rf1

5 V

Vout

Rf2

TSB7191

TSB7192

Vout can be expressed as follows:

VOUT=Rsℎunt.I1− Rg2

Rg2+Rf2 .1−Rf1Rg1 +Ip. Rg2.Rf2

Rg2+Rf2.1+Rf1Rg1 −In.Rf1

−Vio.1−Rf1Rg1

(13)

Assuming that Rf2 = Rf1 = Rf and Rg2 = Rg1 = Rg, can be simplified in the following manner:

VOUT=Rsℎunt.I.RfRg−Vio.1+RfRg +Rf.Iio

(14)

The main advantage of using the TSB7191 and the TSB7192 for a low-side current sensing relies on its low Vio,

compared to general purpose operational amplifiers. For the same current and targeted 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.

TSB7191, TSB7191A, TSB7192, TSB7192A

Typical applications

DS12641 - Rev 5

page 23/34

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