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June 23, 2015

Current sensing accuracy

Iout

Ifb

Ifb leakage

Ifb2

Ifb1

Iout2

Iout1

I offset

The current sensing is specified by measuring 3 points :

- Ifb1 for Iout1

- Ifb2 for Iout2

- Ifb leakage for Iout=0

The parameters in the datasheet are computed with the following formula :

Ratio = ( Iout2

– Iout1 )/( Ifb2 – Ifb1)

I offset = Ifb1 x Ratio

– Iout1

This allows the designer to evaluate the Ifb for any Iout value using :

Ifb = ( Iout + I offset ) / Ratio if Ifb>Ifb leakage

For some applications, a calibration is required. In that case, the accuracy of the system will depends on the variation of

the I offset and the ratio over the temperature range. The ratio variation is given by Ratio_Hot and Ratio_Cold specified in

page 4.

The Ioffset variation depends directly on the Rdson:

I offset@-40°C= I offset@25°C / 0.8

I offset@150°C= I offset@25°C / 1.9

Maximum Vcc voltage with short circuit protection

The maximum Vcc voltage with short circuit is the maximum voltage for which the part is able to protect itself under test

conditions representative of the application. 2 kind of short circuits are considered: terminal and load short circuit.

L SC

R SC

TerminalSC

0.1 µH

10 mohm

LoadSC

L supply + L SC = 5 µH

100 mohm

Out

IPS

Vcc

L SC

L supply

5µH

R supply

10mohm

R SC