UM1556 datasheet(32/87 Pages) STMICROELECTRONICS

32 / 87 page

Analogue current sense

UM1556

32/87

Doc ID 023520 Rev 2

Equation 8

and

Solving these two equations we get the following formulas:

Equation 9

Example for the chosen device:

Setting Iref1 = 2 A and Iref2 = 4 A according to Table 7 we get VSENSE1 = 1.29 V and

VSENSE2 = 2.69 V then

M = 1.43 [S]

b = 0.16 [A]

IOUT is then:

Equation 10

After calibration, the current sense variation is still affected by the device temperature.

Equation 10 remains affected by an error proportional to the sense current thermal drift.

This drift is reported in the datasheet as dK/K.

2.8

Analogue current sense diagnostics

Table 8 summarizes all failure conditions, the VSENSE signal behavior and

recommendations for diagnostics sampling for M0-5 in comparison with M0-5Enhanced.

dK1/K1

(1)

The drift decreases when increasing the output current, e.g. in the VND5E025AK datasheet the drift is +/-

13 % at 2 A and it decreases down to +/-6 % when the output current is 10 A.

Currente

sense drift

IOUT=2 A;

VSENSE=4 V

VCSD=0 V;

Tj=-40°C to 150 °C

-13

ref1

M*V

sense1+b

ref2

M*V

sense2+b

ref1

ref2

–

() V

sense1

sense2

–

()

⁄

ref2∗Vsense1

ref 1∗Vsense2

–

() V

sense1

sense2

–

()

⁄

out

1.43 V

sense

⋅

0.16

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