Circuit Description; Micro Controller Circuit; Deflection Circuit - ViewSonic P774B-2NT Series Service Manual

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MICRO Controller

The IC101 contains a 8031 8-bit CPU core, 60K bytes of RAM, 16K bytes of ROM,14 channel 8 bit

PWM D/A converters, 2 channel A/D converters for key detection,0.5sec watch-dog timer, internal H-

sync and V-sync signals processor providing mode detection, watch- dog timer preventing system from

abnormal operation, and an I²C bus interface.

H/V sync signals processor

The functions of the sync processor include polarity detection, H-SYNC & V-SYNC signals counting,

Programmable SYNC signals output, free running signal generator. Pin41/Pin42 are for the H-SYNC

and V-SYNC input, Pin34/Pin33 will output the same signal as input sync signal without delay, and the

polarity are setting in the positive. When no signal input, the Pin32 will output a 60Hz V-SYNC free run

signal. The Pin33 will output a 48KHz H-SYNC free run signal. for the monitor testing use.

The deflection circuit is achieved by a high performance and efficient solution IC 401 (STV 9118) for

this monitor. The concept is fully DC controllable and can be used in applications with a micro-

controller solutions.

The STV9118 provides sync. Processing with full auto sync. Capability, a flexible SMPS block and an

extensive set of geometry control facilities. Further the IC generates the drive waveforms for DC

coupled vertical boosters to the STV9118.

Horizontal Oscillator

The oscillator is of the relaxation type and requires a capacitor of 1nF C405 at pin29.

PLL 1 Phase Detector

The phase detector is a standard one using switched current sources. It compares the middle of H-

sync. with a fixed point on the oscillator saw-tooth voltage. The PLL loop filter R411,C437,C435 is

connected to Pin9.

PLL2 Phase Detector

The PLL2 detector thus compensates for the delay in the external H-deflection circuit by adjusting the

phase of the HDRV output pulses. The phase between H-flyback and H-sync can be controlled at pin5.

X-ray Protection

5. CIRCUIT DESCRIPTION

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