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TPD7S019, On-chip termination selection for Sync signals

Ryan Andrews
Guru 66266 points
Other Parts Discussed in Thread: TPD7S019

Team,

I'm not sure the best/safest selection to make for the TPD7S019 IC, 65 ohm, 55 ohm, 15 ohm. I saw one post that indicated a series resistor can be used external to the device, but this was back when the only device available was the 15 ohm part.  We are looking to support 1280 x 1024 60Hz signal. We are also using the standard DB-15 VGA connector. I am not sure how to proceed in selecting a device. We do not control the cable the end user of the product chooses, and unless I misunderstand, this really determines which device termination we select.

Can you provide input?

Thanks and regards,

Ryan

  • 0
    TI__Genius 12190 points

    Ryan,

    The TPD7S019 is only offered in the RT = 15 ohm version. If any additional resistance is needed to match network impedance, simply add it at the pin. Of course, please consider any added resistance's affect on rise time and propogation delay. The issue with matching any VGA cable exists no matter which network matching topology you decide to undertake. The TPD7S019 offers an excellent solution for protecting a VGA port from ESD while maintaining signal intergrity.

     

    Kind regards,

     

    Guy Yater

    Integrated Protection Devices

    Application Engineer 

     

     

  • 0 in reply to Guy Yater
    Expert 1215 points

    For 75 ohm cable termination, should I add a 60 ohm series resistor to the line?  If I add a 60 ohm resistor to ground I will create a voltage divider, so I think series is the proper connection method correct?

     

    Thank you,

    Bryan Busacco

  • 0 in reply to Bryan Busacco
    TI__Genius 12190 points

    Hi Bryan,

     

    Yes, the method you have described is correct.

    Regards,

    Guy Yater, Integrated Protection Devices, Application Engineer