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dual pixel LVDS out (DM365)

Mehmet Ugursoy
Prodigy 210 points
Other Parts Discussed in Thread: DS90C387

 

Hi everybody;

I need to Dual pixel LVDS output for bigger then 19" LCD Panels , our processor is dm365 .

as you know dm365 has single 24 bit digital video output, Do you know any chip can i use for dual pixel output ?

 

I found couple of them , these are suitable for using with dm365

 

http://www.national.com/ds/DS/DS90C387.pdf

http://www.ineltek.com/de/files/Explore/LVDSTXRX/ep387a_ug_v07.pdf

http://www.chrontel.com/pdf/7308ds.pdf

 

Thanks

  • 0
    TI__Prodigy 280 points

    Hi,

    I think third IC (chrontel) is not suitable for dual pixel, you should double check .

    Also remember that DM365 can provide max 75MHz pixel clock so this is the upper limit for resolution.

     

  • 0 in reply to Serdar55108
    TI__Genius 14405 points

    Hi,

    Could you confirm what you want is a LVDS transmitter that takes in single source of RGB888 data and sends out two LVDS signals? It doesn't seem that any of the ones you mentioned can do this. In a project that we have in the team, we actually used a FPGA to do something very similar to what you want. Is it something you will be interested in? If so, please ask your regional support to contact us.

  • 0 in reply to Paul.Yin
    TI__Mastermind 43875 points

    As mentioned, the max pixel rate is 74.25MHz.

    All panels I have seen that require dual channel LVDS have pixel rates much higher than this.

    What LCD panel are you trying to use that requires dual channel LVDS, and what resolution is it?

    If the LCD panel truly requires dual channel LVDS then you will need to either pixel double horizontally or use some additional external logic to effectively double the pixel rate.

    If you want to maintain the high resolution then you will need to reduce the frame rate output from the DM365 and use an external frame buffer to frame double so that the pixel clock rate meets the LCD panel minimum spec.

    If you don't care about the resolution then you can either pixel double horizontally or use some external logic to scale a lower resolution source image to meet the LCD resolution (and clock double in the process). This will not require a frame buffer and cheap FPGAs can be used to do the scaling, and often include the LVDS transmitters too, hence offsetting some of the cost.

    BR,

    Steve

  • 0 in reply to Steve Clynes
    TI__Prodigy 280 points

    Hi,

    75MHz means;

    If you will use 640x480 pixel LCD (it should be 800x600 with porch values, you can find this values in your LCD datasheet) at 60Hz (commonly 50-60Hz) refresh rate you need 800x600x60=28800000~=28MHz (you can find pixel clock in your LCD datasheet) clock frequency.

    So 75MHz upper limit,  We can think as 1024x1024x60 ~= 63MHz + porch or 1280x720x60 ~= 55MHz (effective upper resolution limits)

    If you need to use higher resolution LCD you need external solution as Steve mentioned.

    http://processors.wiki.ti.com/index.php/OMAP-L1x/C674x/AM1x_LCD_Controller_(LCDC)_Throughput_and_Optimization_Techniques

     

    Regards

  • 0 in reply to Serdar55108
    TI__Mastermind 43875 points

    As a general rule of thumb the resultant frame rate can be estimated as...

    Pclk / (H x W x 1.2)

    where
    H = height in pixels
    W = width in pixels
    Pclk = pixel clock rate
    1.2 = 'fudge' factor to account for blanking times.

    Depending on the format and the LCD requirements the 1.2 factor can be close to 1.0 or as high as 1.4, but 1.2 is a good estimate.

    http://processors.wiki.ti.com/index.php/Display_Subsystem shows some approximate frame rates for various sizes at 74.25MHz

    BR,

    Steve

  • 0 in reply to Paul.Yin
    Intellectual 345 points

    HI Paul,

    I'm really interested in this soution, I have a 17 inches monitor dual lvds to communicate with DM816 -EVM (RGB888) for a medical application.

    My regional suport  doesn't answer me very quick and they told me to use a dual pixel lvds converter that is not a solution for this appication.

    Could you Help me?

    Best Regards

    Desing Engineer 

    Guilherme Haas

  • 0 in reply to Guilherme Haas
    TI__Genius 14405 points

    Guilherme,

    It seems that the

    http://www.national.com/ds/DS/DS90C387.pdf

    that Mehmet mentioned is a good candidate in your application.

    Please post a new topic in the appropriate (DM816x) forum. DM816x has a more flexible/powerful video out, and i am sure the DM816x support team can help you there.

    Could you please also let us know which region you are in? We would like to escalate it for you and keep your regional support in the loop

    regards,

    Paul

  • 0 in reply to Steve Clynes
    Prodigy 20 points

    Hello,

    I am using the DM368 and I would like to output to a 1920x1080 LCD panel @ 60 Hz. This panel uses 2 channel, 6-bit LVDS communication.

    Based on the above posts, I understand that the 74.25 MHz maximum pixel clock rate on the DM368 means that I cannot achieve this by simple using a dual pixel LVDS interface such as the DS90C387.

    In the above posts however, Paul and Steve mentioned that it is possible for the DM368 to output to a 1080p60 display using an external frame buffer or FPGA. Can you please elaborate on this solution? Are there any recommended devices or reference designs?

    I sincerely appreciate all help,

    Chris