AK8859VQ Datasheet, PDF (18/73 Pages) Asahi Kasei Microsystems – NTSC/PAL/SECAM Digital Video Decoder

[AK8859VQ]
[7.] Functional Description
[7.1.] Analog interface
The AK8859VQ accepts composite (CVBS) and S-Video (Y/C) signals, with 2 input pins available for this
purpose. The decode signal is selected via the register.
Input signal selection
Name
Definition
[AINSEL1 : AINSEL0]
AINSEL0
[00]: AIN1 (CVBS)
~
[01]: AIN2 (CVBS)
AINSEL1
[10]: AIN1(Y) / AIN2(C) (S-Video)
[11]: No-signal input (Analog circuit is set to power-down*)
*Clamp and ADC block is power-downed.
Sub Address: 0x00 [1:0]
Notes
In used with AINSEL[1:0]=[11], Ouput data is depend on NSIGMD[1:0]–bit. However, in used with
NSIGMD[1:0]=[10], DATA[7:0]-pin, HD-pin, VD_F-pin, VAR-pin and VARSUB-pin output Low.
[7.2.] Clock mode
The AK8859VQ input clock can be selected between internal built crystal and external clock input via
register setting. The input clock frequency is 24.576MHz.
Clock mode setting
Name
Definition
CLKMD
[0]: For crystal
[1]: External clock input (clock generator)
Sub Address: 0x00 [7]
Notes
[7.3.] Analog clamp circuit
The analog circuit of AK8859VQ clamps the input signal to the reference level. The way to clamp the input
signal is show as follows.
○ When decode composite (CVBS) video signal
Clamp timing is performs by sync tip clamp (analog sync tip clamp).
The clamp timing pulse, with its origin at the falling edge of the internally synchronized and separated
sync signal, is generated at approximately the central position of the sync signal.
○ When decode S-Video (Y/C) signal
(Y signal): Clamp timing is performs by sync tip clamp (analog sync tip clamp).
The clamp timing pulse, with its origin at the falling edge of the internally synchronized and
separated sync signal, is generated at approximately the central position of the sync signal.
(C signal): Clamp timing is performs by middle clamp (analog middle clamp).
The clamp timing pulse is generated exactly at the same timing of Y signal clamp pulse.
MS1178-E-00
AKM Confidential
- 18 -
2010/04