ICE1QS01
Version 1.4 13 27 Apr 2004
Restart timer
If voltage V
RZI
is lower than 50 mV and gate drive OUT is low an internally created restart pulse will
switch gate drive OUT high every 50 µs and the minimum switching frequency is about 20 kHz.
Restart pulse is inhibited if V
RZI
is higher than 50 mV. So the MOS transistor cannot be switched on
until the transformer is discharged.
VCC overvoltage protection
If V
CC
exceeds the V
CCD
threshold a latch is set and the gate is disabled. Reset of latch occurs
when V
CC
is falling below V
CCon
- V
CCBHY.
Overvoltage fault comparator (OFC)
With an external sense resistor connected to pin OFC primary current can be sensed directly. If the
sensed current exceeds the internal V
OFC
threshold a latch is set and gate is disabled. Reset of
latch occurs when V
CC
is falling below V
CCon
- V
CCBHY
.
Notice: If this comparator is not used pin OFC has to be connected to ground.
Mains undervoltage
Power supplies must be shut down when mains voltage is below a certain limit to avoid too long on-
time of MOS-FET switch, which would lead to a switching frequency in audible spheres. Mains und-
ervoltage is sensed during the off-time of the MOS-FET switch. If the current flowing into pin PCS is
smaller than 100 uA, then the output is latched and cannot be switched to high state.
Diagram Mains Undervoltage Lockout Current
Temp./°C
Ipcs/µA
50
60
70
80
90
100
110
120
130
-40 -30 -20-10 0 102030405060 70 80 90 100 110 120 130 140 150
