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TVP5150AM1 - Vertical sync is not locked

Mark Anzalone
Prodigy 30 points
Other Parts Discussed in Thread: TVP5150AM1, TVP5150

Hello -

We are using a TVP5150AM1 in our video monitor application.  When we connect a NTSC composite source (from a WD TV LIVE Plus) to the AIp1A input, we cannot achieve a Vertical Sync Lock.  i.e. - Status Register 0x88 Reads 0x0A.  Oddly enough we are achieving Horizontal Lock.

We have applied the latest patch (048CAA) and have followed the TVP5150 Quick Start Guide in the design of the Anti-Aliasing circuit and the Crystal Oscillator Circuit as well.

We are programming the following registers at start-up:

Reg  Data

0x03  0xAF
0x07  0x40
0x0D  0x07
0x0F  0x02
0x12  0x04

Can someone please suggest a few other things to check that could cause VSYNC not to lock?

Thanks, in advance, for your help.

Mark

  • 0
    TI__Intellectual 1245 points

    Hi Mark,

     

    Have you verified your input?  This can be done by plugging your source into a monitor.  If there is an issue with the input then there may not be a problem with your TVP5150 setup. 

     

    Thanks,

    Geovid Kali

  • 0 in reply to Geovid Kali
    Prodigy 30 points

    Geovid -

    Thanks for the reply.  Yes, we have verified our input source with several monitors we do not experience any picture quality issues.

    After a little more troubleshooting, we've discovered that out anti-aliasing filter (following the SLEA087A App Note exactly) was the source of our lock problem.  With the anti-aliasing filter circuit bypassed, Reg 0x88 reads 0x0E = Color sub-carrier/Vertical/Horizontal syncs locked.

    Since both the TVP5150AM1 Data Sheet and Quick Start Guide highly recommend the use of an anti-aliasing filter, do you have any other filter design suggestions that we can try?

    Attached is the input circuit to the TVP5150 that we are using in our application.  Please note that through trial-and-error, we have isolated the lock problem to the anti-aliasing filter.

    Thanks, in advance, for your prompt reply.

    Mark A.

    7573.TVP5150_Input_Design.pdf

  • 0 in reply to Mark Anzalone
    TI__Genius 14317 points

    Mark,

    I looked over your schematic and suspected that the source driver AC couple cap might be causing the high pass (AC couple) pole frequency to be above the video vertical frame rate frequency. This could cause the vertical lock problem you see. To confirm, I ran TINA analysis AC transfer function plots and found that this was indeed the case (see attached). DC couple the video driver output (leave 75 ohm source resistor) to the filter input and that should solve the problem.

    TVP5150AM_Input1 (2).zip
  • 0 in reply to Jeffery Pfarr
    Prodigy 30 points

    Jeff -

    Thanks so much for your analysis of out input circuit.  After removing the driver AC coupling cap, the TVP5150 locks perfectly - i.e. Reg 0x88 reads 0x0E.

    We appreciate your help with this.

    Take care,

    Mark Anzalone