Dell UltraSharp 2208WFP, Service Manual

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Service Manual
23
8.3 U850 (
LD7575B
, PWM Power Controller)
Pin Symbol I/O Description
1 RT I This pin is to program the switching frequency. By
connecting a resistor to ground to set the switching
frequency.
2 COMP I Voltage feedback pin(same as the COMP pin in
UC384X).By connecting a photo-coupler to close the
control loop and achieve the regulation.
3 CS I Current sense pin, connect to sense the MOSFET current;
4 GND Ground
5 OUT O Gate drive output to drive the external MOSFET
6 VCC I Supply voltage pin
7 NC Unconnected pin
8 HV I Connect this pin to positive terminal of bulk capacitor the
startup current for the controller. When Vcc voltage trips
the UVLO(on),this HV loop will be off to save the power
loss on the startup circuit;
8.4 U1 ( INL833 , CCFL Inverter controller IC)
Pin Symbol I/O Description
1
VSEN
I
Voltage sense Feedback
2
SSTCMP
I
Capacitor for soft-star and loop
compensation
3
CT
I
Timing resistor and capacitor for operation
and striking frequency
4
RT1
I
Timing resistor for striking frequency
5
GNDA Signal Ground
6
PDR2
O
High side Driver output2
7
GNDP Power Ground
8
NDR2
O
Low side Driver output2
9 NDR1
O
Low side Driver output1
10 PDR1
O
High side Driver output1
11 VDDA
I
Input power Pin
12 TIMER
I
Timing capacitor for Delay Timer
13 PWM
I
External
PWM Dimming Input
14 ISEN
I
Current sense feedback
15 OVPT
I
Over-voltage protection threshold voltage
16 ENA
I
IC
Enable/Disable