Datasheet

VIPER26 Automatic auto restart after overload or short-circuit
Doc ID 17736 Rev 2 17/25
14 Automatic auto restart after overload or short-circuit
The overload protection is implemented in automatic way using the integrated up-down
counter. Every cycle, it is incremented or decremented depending if the current logic detects
the limit condition or not. The limit condition is the peak drain current, I
Dlim ,
reported on
Table 8 on page 7 or the one set by the user through the R
LIM
resistor, as reported in
Figure 13 on page 9.
After the reset of the counter, if the peak drain current is continuously equal to the level I
Dlim
,
the counter will be incremented till the fixed time, t
OVL
, after that will be disabled the power
MOSFET switch ON. It will be activated again, through the soft start, after the t
RESTART
time,
see the Figure 26 on page 17 and the mentioned time values on Table 8 on page 7.
In case of overload or short-circuit event, the power MOSFET switching will be stopped after
a time that depends from the counter and that can be as maximum equal to t
OVL
. The
protection will occur in the same way until the overload condition is removed, see Figure 26
on page 17.
This protection ensures restart attempts of the converter with low repetition rate, so that it
works safely with extremely low power throughput and avoiding the IC overheating in case of
repeated overload events.
If the overload is removed before the protection tripping, the counter will be decremented
cycle by cycle down to zero and the IC will not be stopped.
Figure 26. Timing diagram: OLP sequence
time
time
V
DD
V
DDon
V
DDCSon
I
DRAIN
I
Dlim_bm
t
1
*
* The time t
1
can be lower or equal to the time t
OVL
t
RESTART
t
SS
t
OVL
t
RESTART
t
SS
t
OVL
t
RESTART
t
SS
SHORT CIRCUIT
OCCURS HERE
SHORT CIRCUIT
REMOVED HERE