AUIPS7121R

Current sensing accuracy

Iout

Ifb

Ifb leakage

Ifb2

Ifb1

Iout1

I offset

Iout2

The current sensing is specified by measuring 3 points :

- Ifb1 for Iout1

- Ifb2 for Iout2

- Ifb leakage for Iout=0

the Ifb for any Iout value using :

, the accuracy of the system will depends on the variation of

Ratio_TC specified in page 4.

The Ioffset variation depends directly on the Rdson :

I offset@-40°C= I offset@25°C / 0.8

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

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

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

For some applications, a calibration is required. In that case

the I offset and the ratio over the temperature range. The ratio variation is given by

I offset@150°C= I offset@25°C / 1.9

Out

IPS

Vcc

L SC

L supply

5µH

R supply

10mohm

Terminal SC

0.1 µH

10 mohm

Load SC

10 µH

100 mohm

R SC

www.irf.com

7