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TMDSEMU560V2STM-U: How much current flow on TVRef resistor?

Kei Kuwahara
Expert 5760 points
Part Number: TMDSEMU560V2STM-U

Tool/software:

Hello team,

Customer is selecting the 100ohm resistor for the VTRef pin of the emulation header.
How much current would flow through this resistor?
Customer is asking this question because they have to select the power rating of the resistor.

On the XDS560 Emulator Technical Reference (Rev. A (ti.com), there is 100kohm pulldown on TVD pin, so I am thinking that the current would be small.

Best Regards,
Kei Kuwahara

  • +1
    TI__Guru**** 153549 points

    Hello Kei Kuwahara

    Thank you for the query.

    I suspect this is a customer query.

    If yes, they may have to reach out to blackhawk.

    https://www.digikey.in/en/products/detail/texas-instruments/TMDSEMU560V2STM-U/3588787

    Regards,

    Sreenivasa

  • 0 in reply to Kallikuppa Sreenivasa
    TI__Guru 67830 points

    Kei you definitely can reach out to the emulator vendor but if you are concerned about someone shorting that pin to GND and having the pullup work well then if your VTREF is say 3.3V - a short to ground would be P = V^2/R = 0.11W roughly so that should give an idea of the resistor size you might want so that a short to ground doesn't cause a problem.    So maybe > 1/8W would be a good plan. 

    If you are not worried about the pin being shorted to ground accidentally then in order for the circuit to work and the emulator detect the target, then you know the voltage drop across the 100ohm resistor is going to be something small like 3.3V - 2.7V = 0.6V  and then the power would be 0.004W roughly.  
    So then probably the smallest resistor you can find would be OK if.


    Best Regards,

    Anthony