ViewSonic VX1933W Service Manual page 52

3 LI2
4 COMP
5 FT
6 FSET
7 BOSC
8 DBRT
9 VIN
10 BT
11 TG
12 SW
13 VCC
14 BG
15 GND
16 OV1
ViewSonic Corporation
In single lamp application, connect this pin to LI2 pin.
Lamp current feedback 2. The function of this pin is same as LI1. In
I single lamp application, connect this pin to LI1. In multi-lamp application,
this pin is used for lamp current feedback which is out-of-phase of LI1.
Feedback Compensation Node. Connect a compensation capacitor from
this pin to GND. This pin is also used for IC enable control. A logic low
I
(below 0.5V) input turns off the IC. The enable logic input signal should
have open collector (OC) structure.
Fault Indicator. Connect a capacitor from this pin to GND to program the
I open lamp and short lamp protection delay time. When the voltage on
this pin reaches 1.2V, the IC will shutdown until it is enabled again.
Switching Frequency Set. Connect a resistor from this pin to GND. This
I
resistor sets the operating frequency of the MP1009.
Burst Repetition Rate Setting. Connect a resistor and a capacitor from
this pin to GND. If the burst dimming is to be controlled by an external
I
logic signal, connect BOSC to VCC and apply the logic signal to the
DBRT pin.
Burst-Mode (Digital) Brightness Control Input. The voltage range of 0V to
1.2V at DBRT linearly sets the burst-mode duty cycle from minimum to
I 100%. The minimum burst dimming duty can be programmed by BOSC
resistor and capacitor. If burst dimming is not used, connect DBRT to
VCC.
Input Power Rail. Decouple this pin to GND with >1μF ceramic capacitor.
I
It is desirable to add a 10 resistor between VIN pin and the input bus.
Output Bootstrap. BT provides gate driver bias for the high-side
O
MOSFET. Connect a capacitor from BT to SW.
High-Side MOSFET Gate Output. Connect TG to the gate of the
O
high-side, external power MOSFET.
Bridge Output. Connect SW to the source of the high-side MOSFET and
O
the drain of the low-side MOSFET.
Voltage Rail Output. VCC provides power supply for the low-side gate
O driver and the internal control circuitry. Bypass VCC to GND with a
ceramic capacitor.
Low-Side MOSFET Gate Output. Connect BG to the gate of the low-side
O
MOSFET.
IC ground
Open lamp voltage feedback input. The function of this pin is same as
I
OV2
49 CONFIDENTIAL – DO NOT COPY
VX2433wm-1
VX2433wm-CN