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ADV7802 - Output clock jitter and possible coasting

Hi,

When using the ADV7802 with a 1080i source, it was noticed that there is a large amount of jitter, after the VBI region of the video. This jitter is affecting sensitive backend device.

This noise does not appear to be board/or noise coupling.

Parents
  • The ADV7802 contains coast features which allow it to coast/free-run in the event of missing sync or non-standard input.

    The coast feature is automatically enabled , however manual controls are available.

    CP Map

    0xCC[3] - COAST_MAN_EN

    This control overrides the automatic values and uses.

    This bit changes the coasting mode into a manual mode and also changes the coasting so that it coasts on all lines. Auto mode is only coasting on active video.

    0xCC[2] – COAST_MAN allows you to use manual controls. 

    0xCC[5:4] – Coast lock

    2'b00 = 15 lines

    2'b01 = 31 lines

    2'b10 = 63 lines

    2'b11 =127 lines

    In the question above, the PLL needs to reacquire after active video is recieved, ehich is leading to jitter.

    Rgds,

    Ray

Reply
  • The ADV7802 contains coast features which allow it to coast/free-run in the event of missing sync or non-standard input.

    The coast feature is automatically enabled , however manual controls are available.

    CP Map

    0xCC[3] - COAST_MAN_EN

    This control overrides the automatic values and uses.

    This bit changes the coasting mode into a manual mode and also changes the coasting so that it coasts on all lines. Auto mode is only coasting on active video.

    0xCC[2] – COAST_MAN allows you to use manual controls. 

    0xCC[5:4] – Coast lock

    2'b00 = 15 lines

    2'b01 = 31 lines

    2'b10 = 63 lines

    2'b11 =127 lines

    In the question above, the PLL needs to reacquire after active video is recieved, ehich is leading to jitter.

    Rgds,

    Ray

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