ViewSonic VA712-2, Service Manual, Page: 22 / 77

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
ViewSonic Corporation
Confidential - Do Not Copy
VA712-2_ VA712b-2
19