- SS-HQ1 Application Notes -
Ver.1.0.0 January 7, 2005
53
8.1.1.3. The Input of A/D Converter
Fig 8.1-4 an example of 10 bit-A/D conversion
DRVOUT level = A/D converter input level : Standerd signal level = 400[mV] -> D range of 2.5 times.
The built-in A/D converter of CXD3172AR is an input range 1000m[Vp-p], and can be driven directly by the
outputs of CXA2096N (VRT VRB, DRVOUT).
The input signal of A/D converter is changed into the 10bit -digital signals(= 1024 grade).
The effective maximum value of A/D output signal (high-light side) decreases only the advantages of the
OFFSET (black level) put on DRVOUT.
8.1.1.4. Y,C Signal processing and D/A conversion
Targeting the digital output signal of built-in A/D converter, luminance signal processing, and chrominance signal
processing are done in the CXD3172AR. Finally processed signals are loaded to built-in 10bit-DAC, and
converted to the analog Video signal.
The digital output signal of built-in A/D converter contains both of luminance element and chrominance element.
And the signal is processed suppress, aperture compensation, and gamma, so that the output signal form of
DAC may different from the input signal form of A/D converter. The chrominance output signal is moderated
with sub-career, too. CXD3172AR uses the same analog-cell with Y-DAC, C-DAC.
The luminance signal processing and Y-DAC are described below.
Fig 8.1-5 the standard level of the luminance signal (NTSC)
VRT(2.35[V])
0
1023
VRB(1.35[V])
A/D Conversion
400mV
409[d]
0[d]
1023[d]
VRB
1000mV
100% (Full Scale)
1023[d]
714[d]
D/A Conversion
204[d]
VRT
0[d]
0 %
Gamma
process
Y
process
Sync
20 %
1.0Vpp
(NTSC)
100 IRE
Standard Y Level
160 IRE
(max value)
- 40 IRE
0 IRE
70 %
Standard Y Level
Ext
Video AMP
Video Output