Datasheet

NCL30082
http://onsemi.com
20
At startup, when V
CC
reaches V
CC(on)
, the controller is
not allowed to start pulsing for at least 180 ms in order to
allow the SD pin voltage to reach its nominal value if a
filtering capacitor is connected to the SD pin. This is to avoid
flickering of the LED light in case of over temperature.
S
R
Q
VCCreset
SD
VCC
+
−
Vdd
+
−
OTP_Timer end
noise delay
noise delay
Clamp
Rclamp
Vclamp
Latch
NTC
Dz
OTP
OVP
(OTP latched for version A)
S
R
Q
4−s Timer
OFF
0.5 V if OTP low
0.7 V if OTP high
Figure 51. Thermal Fold−back and OVP/OTP Circuitry
V
OVP
I
OTP(REF)
V
TF
V
OTP
Q
Q
In the case of excess voltage, the Zener diode starts to
conduct and inject current into the internal clamp resistor
R
clamp
thus causing the pin SD voltage to increase. When
this voltage reaches the OVP threshold (2.5 V typ.), the
controller shuts−down and waits for at least 4 seconds before
restarting switching.