L6728D datasheet(14/33 Pages) STMICROELECTRONICS

14 / 33 page

Overcurrent protection

L6728D

14/33

Doc ID 16498 Rev 1

8.1

Overcurrent threshold setting

The L6728D allows easy programming of a 1st level overcurrent threshold ranging from 50

mV to 550 mV, simply by adding a resistor (ROCSET) between LGATE and GND. The 2

level threshold is automatically set accordingly.

During a short period of time (about 5 ms) following VCC rising over UVLO threshold, an

internal 10 µA current (IOCSET) is sourced from the LGATE pin, determining a voltage drop

across ROCSET. This voltage drop is sampled and internally held by the device as a 1

st level

overcurrent threshold. The OC setting procedure’s overall time period is about 5 ms.

Connecting an ROCSET resistor between LGATE and GND, the programmed 1

st level

threshold is:

the programmed 2nd level threshold is:

ROCSET values range from 5 kΩ to 55 kΩ.

In case ROCSET is not connected, the device sets the OCP thresholds to the maximum

values: an internal safety clamp on LGATE is triggered as soon as the LGATE voltage

reaches 600 mV, setting the maximum threshold and suddenly ending the OC setting phase.

OCth1

OCSET

⋅

dsON

--------------------------------------------

OCth2

1.5

OCSET

⋅

dsON

--------------------------------------------

⋅

L6728D 데이터시트(PDF) 14 Page - STMicroelectronics