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TMDS171 - Power dissipation

Kawai
Guru 19775 points
Other Parts Discussed in Thread: TMDS171

Hello Team,

There is a description of power dissipation in the datasheet page 7.

I believe these value include the power dissipation of the internal input termination resistors, am I correct ?

Best Regards,

Kawai

  • 0
    TI__Mastermind 23815 points

    Hi Kawai-san,

    Yes the power dissipation includes the current on termination resistors.

    In DS page 7 there is this note:

    ICC is a direct result of the source design as the TMDS171 integrated receive termination resistor accounts for 85mA to100mA

    Regards

  • 0 in reply to Moises Garcia
    Guru 19775 points
    Hello Moisess-san,

    Sorry that I was not reading the note. Thank you for your great help.

    Best Regards,
    Kawai
  • 0 in reply to Kawai
    Guru 19775 points

    Hi Moises-san,

    Please allow me to confirm a little bit more about the current consumption. Customer is asking us the current consumption excluding the termination resistor portion.

    Q). Is 85mA to 100mA the value of the total current consumption of all four termination resistors ?

    Q). Is current/power consumption of the termination resistor really included ? I believe Vbias is coming from VCC=3.3V. Typ ICC value listed in the datasheet is 80mA at Retimer mode, 50mA at Repeater mode. If you subtract 85mA from those ICC value, the result would be a minus value. How would you explain to this result ?


    Best Regards,
    Kawai

  • 0 in reply to Kawai
    TI__Mastermind 23815 points
    Hi Kawai-san,

    I'm validating this information with characterization team, I'll come back when we have suitable information.

    Regards
  • 0 in reply to Moises Garcia
    Guru 19775 points

    Hi Moises-san,

    Thank you for your continuous support. We look forward to hearing from you soon.

    Best Regards,

    Kawai

  • 0 in reply to Kawai
    TI__Mastermind 23815 points

    Hi Kawai-san,

    The current mentioned in the note 85mA to 100mA is a high range, just to exemplify how high the current consumption can be.

    The typical current consumption of 51mA means: typically current consumption of termination resistors is not in the range 85mA to 100mA.

    Regards

  • 0 in reply to Moises Garcia
    Guru 19775 points

    Hi Moises-san,

    We greatly appreciate for your support. However, our customer request is to understand TMDS171 Maximum and Typical power consumption excluding that of internal termination resistor. This will be the key factor/number for them to decide the device.
    Could you please confirm this number ? It would be better to inform customer ASAP since it have been taking some time.

    We are grateful for your help.

    Best Regards,
    Kawai

  • 0 in reply to Kawai
    TI__Mastermind 23815 points
    Hi Kawai-san,

    We have reviewed the current measurements, these are our conclusions:
    When the device is powered but unplugged from source and sink Icc=0mA.
    The typical Icc values you see in datasheet are average for several data rates and video sources. Those values take into account current in termination resistors. We don't have a current measurement without current in termination resistors.
    The note that is causing confusion has its origin in source devices consuming that amount of current when the device has no sink connected, but TMDS171 is plugged to source. Surprisingly, for these video sources there was more current consumption in termination resistors when no sink was plugged than when there was a video transmission.

    Again these are averages for several video sources and data rates.

    Regards
  • 0 in reply to Moises Garcia
    Guru 19775 points
    Hello Moises-san,

    From my understanding, studying TMDS signaling, the typical differential voltage is 500mV. When High/Low, I assume either of the polarity output would be 3.3V or 3.3V - 500mV = 2.8V, which 500mV is the voltage dropout of the termination resistor (50 Ohm). So, typical current consumption for one differential pair is 500mV / 50 Ohm = 10mA. As HDMI has 4 TMDS pairs so I believe TYP 40mA would be the total current consumption of the internal termination resistors from VCC=3.3V.

    <Current consumption for RETIMER mode>
    ICC1(VCC=3.465V) = 80mA TYP
    IDD1(VDD= 1.27V) = 286mA TYP

    <Current consumption for RETIMER mode excluding that of integrated termination resistors>
    ICC1 = 80mA - 40mA = 40mA TYP
    IDD1 = 286mA TYP

    What do you think of my understanding ?

    Best Regards,
    Kawai
  • 0 in reply to Kawai
    TI__Mastermind 23815 points

    Hi Kawai-san,

    That's a good approach, however you should take into account 80mA is a typical current consumption when device has source and sink connected; when there is source connected but no sink, Icc will vary from 85mA to 100mA, then you subtract 40mA from termination resistors.

    Regards