AK8854VQ Datasheet, PDF (27/95 Pages) Asahi Kasei Microsystems – Multi-Format Digital Video Decoder

14. [CVBSx2, S-Videox4]
CVBS
CVBS
Y₁
Y₂
Y₃
Y₄
C₄
C₃
C₂
C₁
AIN1
AIN2
AIN3
AIN4
AIN5
AIN6
AIN7
AIN8
AIN9
AIN10
AINSEL[7:0] Input Select
[00000000] AIN1 input (CVBS)
[00000001] AIN2 input(CVBS)
[01100010] AIN3(Y) / AIN10(C) input
[00100011] AIN4(Y) / AIN9(C) input
[00011100] AIN5(Y) / AIN8(C) input
[00001101] AIN6(Y) / AIN7(C) input
[AK8854VQ]
7.2 Analog band limiting filter and analog clamp circuit
7.2.1 Analog band limiting filter
The characteristics of the AK8854 internal analog band limiting filter (anti-aliasing), which is in front of
the AD converter input, are as follows:
±1dB (~6MHz )
−22dB (27MHz)….Typical value
7.2.2 Analog clamp circuit
The analog circuit of the AK8854 clamps the input signal to the reference level. The way to clamps the
input signal is as follows.
[CVBS signal decoding]
AK8854 clamps the input signal to sync tip. (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.
[S-video signal decoding]
(Y signal)
AK8854 clamps the Y signal to sync tip. (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)
AK8854 clamps the C signal to the middle level. (analog middle clamp)
The clamp timing pulse is generated at same timing with Y signal.
[YPbPr signal decoding]
The way to clamps the input signal at YPbPr signal decoding can be set by register as follows.
YPBPRCP-bit: Select the way to clamps the input signal at YPbPr signal decodeing.
YPBPRCP-bit
Clamp
Notes
[0]
Y: analog sync tip clamp
Pb, Pr: analog backporch clamp
[1]
Y: analog sync tip clamp
Pb, Pr: analog middle clamp
*
*If Pb and Pr signal have sync signal, analog middle clamp must not be set .
The analog backporch clamp timing pulse is generated at approximately the central position of the
backporch interval.
MS0973-E-01
27
2008/07