AnsweredAssumed Answered

ADV7391 video undershoot

Question asked by Valeri.P on Jan 8, 2013
Latest reply on Jan 16, 2013 by PaulS

Hello

We see a strange behaviour of the ADV7391. It operates in 8 bit YCbCr input mode and CVBS output on DAC1. We use the IC with the ADA 4430 (low current mode). The video data comes from FPGA that converts it from RGB to YCbCr 4:2:2 format.

With some data patterns there is an undershoot at active video start and active video end (we see it on scope at the DAC output). What can be the problem? Can it be related to RGB to YCbCr conversion we perform?

Additionally I see that in our circuit Rset = 3.83k and Rload = 274Ohm - that is not according to your requirements, but it was not designed by me, so I don't know why the resistors values were changed. Can it cause the problem I describe above? Shall I change them or not.

Thanks

Valeri

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