Datasheet

NCL30082
http://onsemi.com
22
4−s Timer
Figure 53. Thermal Fold−back / OTP Chronograms
I
out
V
OTP(off)
V
TF(stop)
V
SD
V
DRV
V
CC
V
CC(on)
V
CC(off)
V
CC(reset)
V
TF(start)
V
SD
> V
TF(stop)
and
V
CC
> V
CC(on)
:
DRV pulses restart
4−s timer has elapsed
but V
SD
< V
TF(stop)
≥ no restart
V
SD
< V
OTP(off)
:
controller stops
switching
PWM or Linear Dimming Detection
The pin DIM allows implementing either linear dimming
or PWM dimming of the LED light.
If the power supply designer apply an analog signal
varying from V
DIM(EN)
to V
DIM100
to the DIM pin, the
output current will increase or decrease proportionally to the
voltage applied. For V
DIM
= V
DIM100
, the power supply
delivers the maximum output current.
If a voltage lower than V
DIM(EN)
is applied to the DIM pin,
the DRV pulses are disabled. Thus, for PWM dimming, a
PWM signal with a low state value < V
DIM(EN)
and a high
state value > V
DIM100
should be applied.
The DIM pin is pulled up internally by a small current
source. Thus, if the pin is left open, the controller is able to
start.
0%
100%
PWM dimmingAnalog dimming
Figure 54. Pin DIM Chronograms
V
DIM
I
out
I
out
V
DIM(EN)
V
DIM100
Note:
• If a PWM voltage with a high state value < V
DIM100
is
applied to the DIM pin, the product will still be in
PWM dimming mode, but the reference voltage will be
decreased according to V
DIM
. This allows increased
dynamic range on the dimming control pin.
• Thermal Foldback and dimming: if the IC is in a
dimming state and the thermal foldback (TF) is
activated, the output current is further reduced to a
value equal to Dimming*TF.