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Do Multiple Powerdowns of the ADV728x Distort the output?

Question asked by Rob.Analog on Nov 18, 2016

The following applies to the ADV7182, ADV7280, ADV7280-M, ADV7281, ADV7281-M, ADV7281-MA, ADV7282,  ADV7282-M and ADV72823.

 

When performing multiple Powerdown commands on the ADV728x (i.e. putting the ADV728x into and out of powerdown mode multiple times quickly) you may notice that the output from the ADV728x will become distorted.

 

The color information may be swapped (red outputs appear blue), the output appears black and white, or the output image is very noisy.

 

Unfortunately the toggling the powerdown command repeatedly will cause the ADV728x digital core to go into an undetermined state. This results in distorted output video.

This is true if the powerdown pin or the powerdown bit is used.

 

The only way to prevent this issue is to perform a software or hardware reset after the powerdown feature is used. i.e. perform the following sequence. 

 

1) powerdown the ADV728x

2) exit powerdown

3) reset the ADV728x

4) Exit reset and reprogram the ADV728x

 

ADV728x documentation will be updated with this information.

 

regards,

Robert Hinchy,

Applications Engineer,

Analog Devices Inc.

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