Datasheet

VIPER06 Automatic auto-restart after overload or short-circuit
Doc ID 022794 Rev 1 19/28
14 Automatic auto-restart after overload or short-circuit
The overload protection is implemented automatically using the integrated up-down counter.
Every cycle, it is incremented or decremented depending upon the current logic detection of
the limit condition or not. The limit condition is the peak drain current, I
Dlim ,
given in Tabl e 7
on page 8 or the one set by the user through the R
LIM
resistor, shown in Figure 13 on
page 11. After the reset of the counter, if the peak drain current is continuously equal to the
level I
Dlim
, the counter will be incremented until the fixed time, t
OVL
, at which point the power
MOSFET switch ON will be disabled. It will be activated again through the soft-start after the
t
RESTART
time (see Figure 25 and Figure 26 on page 19) and the time values mentioned in
Table 7 on page 8.
For overload or short-circuit events, the power MOSFET switching will be stopped after a
period of time dependent upon the counter with a maximum equal to t
OVL
. The protection
sequence continues until the overload condition is removed, see Figure 25 and Figure 26.
This protection ensures a low repetition rate of restart attempts of the converter, so that it
works safely with extremely low power throughput and avoids overheating the IC 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 25. Timing diagram: OLP sequence (IC externally biased)
Figure 26. Timing diagram: OLP sequence (IC internally biased)
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
time
time
V
DD
V
DDon
V
DDCSon
I
DRAIN
I
Dlim_bm
t
1
*
* The time t
1
can be lower than 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