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TVP5158 Display Issue

Mickey Zhang
Genius 12080 points

Other Parts Discussed in Thread: TVP5158

Hi Team,

The customer is using TVP5158. The video display is OK. But when he uses N or P to collect images, there are a red stripe, a stripe yellow and a blue stripe on the camera.  The supply voltage are 3.3V, 1.8V and 1.1V for  TVP5158. The ripple for the supply voltage is below 50mV.

The system framework is "the camera--TO---TVP5158---TO---DM6437--TO---Video display“. His project applies in the Car Panoramic System.

Look the attachment. They are the stripe images and the customer's schematic.

Q1: How much is the ripple for the TVP5158 supply voltage OK?

Q2: What is the reason? How to solve the issue? Is the issue  the analog to digital conversion issue for TVP5158? 

Thanks,

Best Regards,

5483.TVP5158_sch.pdf

  • 0
    TI__Mastermind 43875 points

    This is more likely noise on the actual video signal.

    If possible try the following tests...

    Test #1

    Remove the input coupling capacitor on the Vin_x connection.

    Connect a shielded wire, as short as possible, from the capacitor connection (signal side) to a TV/monitor CVBS input to see if there is any noise at the TVP input.

    Test #2

    Replace the capacitor removed in #1

    Short the ground signals in as many places as possible. Different grounds requires VERY careful layout and most often causes more issues than it solves.

    Test #3

    Take a known good source signal (checked by looking at it on a TV/monitor and wire DIRECTLY  to the decoder input coupling capacitor (solder across e.g. C135 and remove L11)

    BR,

    Steve

  • 0 in reply to Steve Clynes
    TI__Genius 12080 points
    Hi Steve,
    Thanks for your reply.
    For Test #1, what are the coupling capacitors in the customer's schematic? Are they C136/C138/C144/C148 OR C133~C135/C139~C141/C145~C147/C149~C151?

    For Test #2, sorry, I can not understand what your mean is. Can you explain again and give me an example in the customer's schematic?

    For Test #3, sorry, I can not also understand what your mean is. Can you explain again and give me a sketch map?
  • 0 in reply to Mickey Zhang
    TI__Mastermind 43875 points

    For #1, the coupling capacitors are the ones which AC couple the signal to the TVP input, so C136, C138, C144 & C148

    For #2, this is a layout test. Their schematic shows split ground planes (GND_DENC and the system ground). Try shorting these together in as many places as possibly. Also, try shorting L24. I think there are possibly ground loops and/or signal loops causing noise.

    For #3, what is the source of the video signal being tested? Take this source and plug into a TV/monitor to make sure IT is clean. Next, remove the connector of the source cable and wire it directly into the input of the coupling capacitor of the TVP, thus eliminating all other potential ground loops and input signal noise.

  • 0 in reply to Steve Clynes
    TI__Genius 12080 points
    Hi Steve,
    OK. I will tell the customer and if the customer has the test results, I will tell you.