ViewSonic VA702-3 Service Manual page 19

Oscillator with an active current sense circuit. Desired output voltage are determined by the equation,
Volt = 1.25 ( 1 + R67 / R66), In this case, the output voltage are 3.3 Volts
The AIC1739 is a low dropout positive adjustable regulator with minimum of 300mA output current capability.
So it is well suited for 3.3 V and 2.5 V Regulator.
6.1.3 Power Regulator MC34063A (U7) : The MC34063A is a monolithic control IC containing the primary functions required for DC
to DC converters. The device consists of an internal temperature compensated reference, comparator, controlled duty cycle.
Oscillator with an active current sense circuit. Desired output voltage are determined by the equation,
Volt = 1.25 ( 1 + R85 / R86), In this case, the output voltage are 5.0 Volts for panel power.
6.2 Power(Inverter) Board
This is a specific power(inverter) power board for VA702-3 monitor 40W 12V 3.5A output power and backlight which
converters 12 Vdc to drive four cold cathode fluorescence tubes.
6.2.1 Inverter Electrical specification described as below.
Rated Input Voltage
Input
Input Voltage Range
Input Current
On / Off control Voltage
Output Rated Output Strike-on Voltage
Rated Output Voltage
Rate Output Frequency
Rated Ourput Current
6.2.2 power
This is a general purpose AC / DC adapter which converter 90~240 Vac to a stabilized DC voltage 12 V with rated output
current of 4.16A . Electrical specification described as below.
Rated Input Voltage
Operation Input Voltage
Input Current
Inrush Current
Standby Input Voltage
Output Voltage Regulation
Output Ripple & Noise
Rate Output Current
Turn-on delay
ViewSonic Corporation
12Vdc
11.4 ~ 12.6 Vdc
<2A
2~3.3 for on , 0~1 for off
1500Vrms
710Vrms at 7mA
40~50KHz
7~8 mA
90~240 Vac , 50 / 60Hz
90~260 Vac , 47 ~ 63Hz
<1.5A
<100A@120Vac
12Vdc
+/-5%
120mVp-p
<3.5A
<3secs
Confidential - Do Not Copy
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VA702-3_VA702b-3