L6728 datasheet(12/31 Pages) STMICROELECTRONICS

12 / 31 page

Over current protection

L6728

12/31

Over current protection

The over current function protects the converter from a shorted output or overload, by

sensing the output current information across the low side MOSFET drain-source on-

resistance, RDS(on). This method reduces cost and enhances converter efficiency by

avoiding the use of expensive and space-consuming sense resistors.

The low side RDS(on) current sense is implemented by comparing the voltage at the PHASE

node when LS MOSFET is turned on with the programmed OCP thresholds voltages,

internally held. If the monitored voltage is bigger than these thresholds, an over current

event is detected.

For maximum safety and load protection, L6728 implements a dual level over current

protection system:

●

1st level threshold: it is the user externally set threshold. If the monitored voltage on

PHASE exceeds this threshold, a 1st level over current is detected. If four 1st level OC

events are detected in four consecutive switching cycles, over current protection will be

triggered.

●

2nd level threshold: it is an internal threshold whose value is equal to 1st level

threshold multiplied by a factor 1.5. If the monitored voltage on PHASE exceeds this

threshold, over current protection will be triggered immediately.

When over current protection is triggered, the device turns off both LS and HS MOSFETs in

a latched condition.

To recover from over current protection triggered condition, VCC power supply must be

cycled.

L6728 数据表(PDF) 12 Page - STMicroelectronics