AK8855 Datasheet, PDF (15/81 Pages) Asahi Kasei Microsystems – NTSC/PAL Digital Video Decoder

[ASAHI KASEI]
AK8855
Functional Outline
(1) Clock
Feed a 24.5454 MHz clock. When a 27 MHz clock is required, it is generated by an internal PLL.
Internal operating clock rates are :
24.5454 MHz at VGA / QVGA / rotated QVGA size / rotated CIF size outputs
27 MHz
at 601 Pixel mode, CIF / QCIF
Although clock is asynchronous with input signal, Vertical position is aligned since Digital Pixel Interpolator is
integrated on-chip
(2) Analog Interface
The AK8855 accepts Composite Video signal.
(3) Input Signal
NTSC-M,PAL-B,-D, -G, -H, -I compatible Composite Video signals are accepted as input signal.
(4) Analog Input Signal Processing
Anti-aliasing filter is integrated on-chip.
PGA
: 0 dB ~ 12 dB ( approximately 0.1 dB / step )
AD Converter : operation at either 24.5454 MHz or 27.00 MHz
(5) Clamp Processing
Sync-Tip Clamping is processed in Analog part and Digital Pedestal Clamping in Digital Signal Processing
part.
(6) Adaptive AGC Function
Based on the difference between the Sync-Tip level and Pedestal level, input signal value is corrected to a
proper level.
A function to adjust gain by Video signal level is integrated for such a case where only the Video signal is
larger.
(7) ACC Function
Based on the Color Burst level, input Color signal level is corrected to a proper level.
(8) Y / C Separation Function
Primary Y / C separation is done.
(9) Pixel Interpolator
The AK8855 has an on-chip Digital Pixel Interpolator to align output pixels’ vertical position. Therefore no
line-synchronized clock etc are required.
(10) Picture Quality Adjustment Function
Adjustments of Contrast, Brightness, Color Hue and Color Saturation levels are possible.
(11) Output Interface
Outputs are ITU-R BT.601 compatible signal levels ( with limit ON / OFF ).
Output interfaces are shown as follows :
- supporting Camera I / F
- ITU-R BT.656-like output format *
- Active Video region is indicated by HD / VD ( FIELD ) / DVALID
* with SAV / EAV, at 27 MHz output. There is a case where number of clock count from EAV to SAV may differ
from Rec.656 format.
MS0319-E-03
15
2004 / 11