ViewSonic VX1933W Service Manual page 51

4.6 Key Parts Pin Assignment
4.6.1 IC802 (TOP245Y or TOP246Y, Power Control IC)
Pin Symbol
1 BO
2 FB
3 CS
4 GND
5 DRV
6 VCC
7 NC
8 HV
4.6.2 IC501 (OZ9938GN, CCFL inverter controller IC)
Pin No. Symbol
1 OV2
2 LI1
ViewSonic Corporation
I/O
I Brown-out and external triggering
I Sets the peak current setpoint
I Current sense input and overpower compensation adjustment
IC ground
O Output driver
I IC supply
I High-Voltage pin
I/O
Open lamp voltage feedback input 2. Connect a capacitive voltage
divider from the hot terminal of the lamp to ground. Connect this pin to
the tap on the divider and a bias resistor to VCC. In multi-lamp
application, connect a diode from each lamp capacitive voltage divider
which is in-phase to each other to this pin. If the peak voltage value at
OV2 pin exceeds +13V, the controller will treat this as lamp overvoltage
I condition. A pulse of current will pull-down on the COMP pin to regulate
the lamp voltage. The burst dimming signal will be ignored and the Fault
Timer will start ramping up. This signal is also used for short circuit
protection. If the voltage at OV2 is always above 4.9V, the controller will
treat this as a short circuit condition after a certain delay. The Fault Timer
will start ramping up. In single lamp application, connect this pin to OV1
pin.
Lamp current feedback 1. Connect this pin to the current sense resistor.
In multi-lamp application, connect a diode from this pin to each lamp
current sense resistor which is in-phase to each other. These diodes
forms an AND gate with an internal 60uA pull up current source.
Combined with the lamp current feedback signal from LI2, the signal is
I
fed to the internal error amplifier. Selecting the feedback resistors can
easily program the lamp current. The signal is also used for open lamp
protection. If the voltage at LI1 is always below 1.15V, the controller will
treat this as an open lamp condition after a certain delay. The burst
dimming signal will be ignored and the Fault Timer will start ramping up.
48
Description
Description
CONFIDENTIAL – DO NOT COPY
VX2433wm-1
VX2433wm-CN