The AD9826 has a power down bit in the configuration register.
How fast can the ADC wake-up again and begin to make measurements after power-down?
Please refer below comments,
How much time does the AD9888 need to settle on the video signal and deliver a stable video data output
after the converter is taken out of power-down mode ?
Estimated that it takes about 20mS to achieve a stable image out once the
power down bit is de-asserted.