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Problem for ADV7343

Question asked by gongjiulu on Jan 21, 2015
Latest reply on Jan 29, 2015 by gongjiulu

Hi, we got two problems when using ADV7343 for video encoder (the output is video in form of PAL). Attached please find our design; we have ten of the same custom hardware using the same design, among which eight work well and the other two don’t. For all of the custom hardware, we use oscilloscope to measure the signal amplitude for pin 39 (DAC_D) when start to power the hardware, which are shown in Fig. 1 and Fig. 2. According the manual, “The VDD_IO power supply must be established a minimum of 250 μs prior to the VDD power supply being established.”, and for our custom hardware, the Power Supply Sequencing result is shown in Fig. 3.

 

Fig1.jpg

Fig.1

Fig2.jpg

Fig.2

Fig3.jpg

Fig.3

The custom hardware which cannot work has the following problems:

For the first one, we can get video output from ADV7343, but the video is darker the normal one. If we oscilloscope to measure the signal amplitude, it is lower than normal, and the peak to peak amplitude is 300mv.

 

For the second one, we cannot get video output from ADV7343, and the video is all black.

 

Can you tell me the possible reasons for the fail, and how to improve our design? Thanks

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