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TFP401APZP For Low Resolution Display

Steven Gunther
Prodigy 20 points
Other Parts Discussed in Thread: TFP401A, TFP401

I have a 480x272 TFT that I would like to drive using a DVI source.  Assuming my math is correct to drive the display at 60Hz would require an input clock of ~9MHz.  Is there any way to use the TFP401A with this display without some intermediate scaling chip?

I built up an interface circuit card for this purpose and without driving a signal into the TFP401A the LCD is displaying a rolling screens of Red, Green, Blue, Black, White and finally a checkerboard pattern.  When I drive the screen with my 480x272 DVI source at 60Hz I get a white screen.

Any help/thought would be appreciated.  If possible is there a TI FAE that I can work with directly on this issue?

Respectfully,

-Steve Gunther

Display Data Sheet;

http://www.newhavendisplay.com/specs/NHD-4.3-480272EF-ATXL.pdf

  • 0
    Prodigy 20 points

    After some more work tonight I got the display to work.  I had to increase the LCD refresh rate to 160 Hz to bring the OCLK to 25 MHz which is within spec according to the data sheet and then everything started working.  The faster clock is out of spec for the display but it is working.  

    So I guess my question now is centered around the ability to use the TFP401 at lower clock rates than 25 MHz.  Assuming I wanted the lower clock rates is there any method to using the TFP401 or similar chip to achieve clock rates lower than <= 14MHz?

    Respectfully,

    -Steve Gunther

  • 0 in reply to Steven Gunther
    TI__Genius 11020 points

    The TFP401 may have issues getting the PLL to lock at frequencies lower than ~15MHz.  The spec is 25MHz, but the design has some margin, but the low input frequency cut-off  is ~15MHz, there is no mode the TFP401 to reduce this.  I'm not as familiar with some of the other devices so I can't really offer any sugestions in that area.