NCP1239
Fault Management
New Startup
attempt
Fault confirmed
100ms*
Fault not confirmed
100ms*
4.3V
10ms* Jittering
3.0V
1.8V
fmax
fmin
OVL signal
(Over−Load)
0.9 V
Error flag
0.9 V
Error flag
0.9 V
Error flag
Reset at UVLO
PFC off
PFC off
PFC on
DRV
Vcc
16.4V
11.2V
Fault occurs here
6.9V
Fb is ok
*This time is programmed by the Pin 6 capacitor. C
= 390 nF nearly sets the following intervals:
pin6
− Soft−Start Time (T ):7.5 ms
ss
jittering
− Jittering Period (T
): 10 ms
− Fault Detection Delay (T
): 100 ms
delay
More generally, the times approximately depend on C
as follows:
pin6
− T = 7.5 ms * C
/ 390 nF
ss
pin6
− T
− T
=10 ms * C
=100 ms * C
/ 390 nF
jittering
pin6
pin6
/ 390 nF
delay
Figure 33. Fault Management
http://onsemi.com
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