Datasheet

L6375S Electrical specifications
Doc ID 12603 Rev 8 9/17
2.8 Overcurrent operation
In order to implement a short-circuit protection the output Power MOSFET is driven in linear
mode to limit the output current to the I
sc
(1.1 A typical value). This condition (current limited
to the I
sc
value) lasts for a T
on
time interval, that can be set by means of a capacitor (C
don
)
connected to the ON DELAY pin according to the following formula:
T
on
= 1.28 μsec/pF
for
50 pF< C
don
< 2 nF
After the T
on
interval has expired the output Power MOSFET is switched off for the T
off
time
interval with:
T
off
= 64 ·T
on
.
When also the T
off
interval has expired, the output Power MOSFET is switched ON. At this
point in time two conditions may occur
a) The overload is still present, and then the output Power MOSFET is again driven
in linear mode (limiting the output current to I
sc
) for another T
on
, starting a new
cycle, or
b) the overload condition is removed, and the output Power MOSFET is no longer
driven in linear mode. All these occurrences are presented on the DIAG2 pin
(see Figure 2).
This unique feature is called non-dissipative short-circuit protection and it ensures a very
safe operation even in permanent overload conditions. Note that choosing the most
appropriate value for the T
on
interval (i.e. the value of the C
don
capacitor) a delay (the T
on
itself) prevents misleading short-circuit information being presented on the DIAG2 output,
when driving capacitive loads (that acts as a short-circuit in the very beginning) or an
incandescent lamp (a cold filament has a very low resistive value). The non-dissipative
short-circuit protection can be disabled (keeping T
on
= 0 but with the output current still
limited to I
sc
, and diagnostic disabled) simply shorting to ground the ON DELAY pin.
Figure 4. Non-dissipative short-circuit protection operation