Here is what I was given from the team: Linearity does not change as a function of PGA. However ADC output will be noisier as PGA gain increases: because at high gain any noise at the analog input will be amplified. CCD cells ideally should have no charge at completely dark (optical black) condition, however in reality they have a non-ideal leakage. In order to achieve maximum dynamic range TLV990 samples this optical black offset from CCD cells that are physically covered. Then they are subtracted from the video signal. That way maximum dynamic range is achieved (especially for low-light applications). Since different CCD sensors may use different optical cells, a signal (OBCLP) is needed to tell TLV990 when to sample optical black cells. Optical black compensation is different from CDS(correlated double sampling). CDS samples two different levels within the same pixel. Optical black samples multiple pixels to obtain average offset, and this value is used to compensate for offset each line. Timing chart and explanations for these signals are given in data sheet. CLCCD,BLKG, and OBCLP timing depend on specific requirements of CCDs. Accuracy is in terms of pixels. ADCCLK, SR and SV depend on timing of 1 pixel and accuracy requirement is sub-pixel. I hope that helps.
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