STMicroelectronics 12 V, 150 mA non-isolated buck converter using VIPer™ Plus - VIPER06XS STEVAL-ISA115V1 STEVAL-ISA115V1 Data Sheet
Product codes
STEVAL-ISA115V1
DocID024275 Rev 2
15/29
AN4260
Functional check
After the short removal, the IC resumes working normally. If the short is removed during t
SS
or t
OVL
, before the protection tripping, the counter is decremented on a cycle-by-cycle basis
down to zero and the protection is not tripped.
If the short-circuit is removed during t
RESTART
, the IC must wait for the t
RESTART
period to
elapse before switching is resumed
6.3
Feedback loop failure protection
This protection is available any time the IC is externally biased. As the loop is broken (R4
shorted or R5 open), the output voltage V
shorted or R5 open), the output voltage V
OUT
increases and the VIPER06XS runs at its
maximum current limitation. The VDD pin voltage increases as well, because it is linked to
the V
the V
OUT
voltage through the diode Daux.
If the V
DD
voltage reaches the V
DD
clamp threshold (23.5 V min.) in less than 50 msec the
IC is shut down by open loop failure protection (see
and
), otherwise by
OLP, as described in the previous section. The breaking of the loop has been simulated by
shorting the low-side resistor of the output voltage divider, R4 = R4a1+R4b. The same
behavior can be induced opening the high-side resistor, R5 = R5a+R5b.
shorting the low-side resistor of the output voltage divider, R4 = R4a1+R4b. The same
behavior can be induced opening the high-side resistor, R5 = R5a+R5b.
Figure 23. Output short-circuit applied: OLP
tripping
Figure 24. Output short-circuit maintained: OLP
steady-state
Output is shorted here
Normal
operation
t
OVL
t
RESTART
I_L2
AM16649v1
t
RESTART
I_L2
AM16650v1
Figure 25. Output short-circuit maintained: OLP
steady-state (zoom)
Figure 26. Output short-circuit removal and
converter restart
t
OVL
I_L2
AM16651v1
t
OVL
t
RESTART
Normal
operation
Output short is
removed here
I_L2
AM16652v1