Ripple (pseudo outline made by quantized error) occurres on the point which swithing the ADC output multiple bit in
parallel. When switching the several of ADC output at the same time, ripple (pseudo outline caused by miss
quantization) occurs to the image.
Differential code and gray code are recommended for this countermeasure.
Figure 9 indicates circuit block. When luminance signal changes are smoothly, the number of bit of switching digital
output bit can be reduced and easily to reduce the ripple using this function.
This function is especially effective for longer the settings of sensor more than clk = 30 kHz, and ADC output.
Figure 10 indicates the timing specifications.
10 Differential SW(D5)
Figure 9 Differential Code, Gray Code Circuit
(In case of select the positive edge of ADCLK with D8)
(In case of select the positive polar)
(Beginning edge of OBP and standard edge of ADCLK should be exept ±5 ns)
1 2 3 4 5 6 7 8 9 10 11
Figure 10 Differential Code Timing Specifications
To use differential code, complex circuit is necessary at DSP side.
(1) Differential coded
(2) Gray → Binary conversion
Figure 11 Complex Circuit Example
Rev.1.0 Apr 20, 2004 page 15 of 21