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ADV7842 Analog inputs disturbances

Question asked by Yannick.C on Sep 23, 2011
Latest reply on Oct 11, 2011 by Yannick.C



I use the ADV7842-ADV7511 evaluation board in revision 1.1.

I have an analog RGB HV computer signal at 1600x1200@60 resolution (162 MPixels) on HD15 input.

I have configured ADV7842 to work in auto-graphics mode with AIN_SEL to 0.


When I display the ADV7511 HDMI output on a screen with a “GRID” pattern, there is a ghost column after each grid white column that appears exactly after the time treatment of the ADV7842 (cf. ANALOG_ON_OUTPUT.jpg).


In my case the ghost comes 130 nanoseconds after the good pixel, and delay between input H and output H is 130 nanoseconds too (cf. GR_G_IN_Analog_RGBHV_1600_1200_60.jpg). For example when I enable YUV to RGB conversion, it adds delay to treatment and the ghost is delayed too.

Even if I set the drive of data to lowest, the ghost intensity is decreased but still visible. If I set output data to tri-state, analog input signal is clean.

Furthermore if I use HDMI 1 inputs with the same signal (GRID at 1600x1200@60) and displayed it (cf. HDMI_ON_OUTPUT.jpg), analog signals have the same disturbance (cf. GR_G_IN_HDMI_1600x1200_60.jpg) but with the delay of HDMI treatments (405 nanoseconds).


So it is sure that output bus disturbs at least analog AIN1, AIN2 and AIN3 signals. I just want to know if that problem comes from the evaluation board implementation or a problem of signal segregation in the ADV7842 ?


Best regards,