ViewSonic VA712b-2, Service Manual

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ViewSonic Corporation
4.4 INTRODUCTION OF IC
RTD2523B-LF(U401): integrate ADC, OSD, TMPS, RSDS TX, LVDS TX, convert
analog RGB into digital and room and shrink scaling output to LCD panel.
PIN Function:
AIC1084-33PM (U701): DC power convert, used to 5v convert 3.3v.
Pin Symbol Description
127 XO Crystal OSC output
128 XI Reference clock input from external crystal or from
single-ended CMOS/TTL OSC
（ 3.3V tolerance ）
50
DDCSCL1 （ ADC ） Open drain （ Internal 75K pull high ）
51
DDCSDA1
（
ADC
）
Open drain
（
Internal 75K pull high
）
121
DDCSCL2
（
DVI
）
Open drain
（
Internal 75K pull high
）
120
DDCSDA2
（
DVI
）
Open drain
（
Internal 75K pull high
）
123 RESET_OUT Reset out Open drain( internal 75KOhm high)
110/48 COUT Crystal out
124 33VRST_REF Reference 3.3V for Reset Out
109 33VPNLOUT
Panel on/off switch out
（
Max current driving 1A
）
58 BJT_B Embedded regulator P type BJT control pin out
5 TMDS_TST TMDS_TEST Pin;
Power-on-latch for host interface type.
7/13 TMDS_VDD
TMDS power
（
3.3V
）
6 REXT Impedance Match Reference.
49/112 PWM2
4/48/111 PWM1
3/5/122 PWM0
4 BYPASS For External Bypass Capacitor
125 DPLL_VDD
Power for digital PLL
（
3.3V
）
2 APLL_VDD
Power for multi-phase PLL
（
3.3V
）
3 PLL_TEST1 Test Pin 1;Power-on-latch for MCU crystal location
4 PLL_TEST2 Test Pin 2;Power-on-latch for crystal in frequency
56/118 SCSB
Serial control I/F chip select
（
Open drain
）
57/119 SCLK
Serial control I/F clock
（
Open drain
）
59/83/108 Pad 3.3V Power PVCC
47/116 Digital 1.8V Power VCCK
21/38 ADC_VDD
ADC Power
（
1.8V
）
40 VCLK Video8 Clock
19 AVSO ADC vertical sync input
5V tolerance
Power from PIN 13
20 AHSO ADC horizontal sync input
Adjustable Schmidt trigger 5V tolerance
Power from PIN 13