L6377 datasheet(10/16 Pages) STMICROELECTRONICS

10 / 16 page

Over current operation

L6377

10/16

When also the tOFF interval has expired, the output power MOS is switched ON.

Now two conditions may occur

●

the overload is still present. In this case the output power MOS is again driven in linear

mode (limiting the output current to Isc) for another tON, starting a new cycle, or

●

the overload condition is removed, and the output power MOS is no longer driven in

linear mode.

All these occurrences are presented on the DIAG pin (see fig 5). We call this unique feature

non dissipative short circuit protection and it ensures a very safe operation even in

permanent overload conditions. Note that, of course, choosing the most appropriate value

for the tON interval (i.e. the value of the CDON capacitor) a delay (the tON itself) will prevent

that a misleading Short Circuit information is presented on the DIAG output, when driving

capacitive loads (that acts like short circuit in the very beginning) or Incandescent Lamp (a

cold filament has a very low resistive value).

The non dissipative short circuit protection can be disabled (keeping tON = 0 but with the

output current still limited to Isc, and Diagnostic disabled) simply shorting to ground the the

ON DELAY pin.

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