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TPA3245: Allowable operating voltage at 8Ω load

Part Number: TPA3245
Other Parts Discussed in Thread: TPA3255, TPA3251, TPA3244, TPA3250

For BOM reasons, we would like to consider the TPA3245 for a powered speaker application. I've noticed the part is not really spec'd for 8Ω, assumedly due to its lower recommended operating voltage, even though it is a pad-up device. Assuming we're using a 6Ω to 8Ω load, would we be safe running PVDD at 36 volts IN THIS LOAD APPLICATION, given adequate heatsinking?

Also, I assume the 3245, 50, 51 & 55 are pin for pin (other than the pad down on the 50)?


  • Hi Bob,

    Actually we don't really have a maximum impedance for TPA32xx. If you look at the measurement graphs in the TPA3245 datasheet, you can actually see we tested with 8Ω.

    So while above the recommended voltage range, 36V is within the absolute maximum ratings (seen on page 5).
    If you are wanting to see the effects of PVDD vs Output power, we actually have a graph on page 10 of the datasheet that shows this with an 8Ω load. It doesn't go up to 36V but I would still highly recommend looking at it to get a better idea of the effects of PVDD on output power.

    You are correct:
    - The pad ups: TPA3245, TPA3251, and TPA3255 all are pin compatible.
    - The pad downs: TPA3244 and TPA3250 are pin compatible.

    I would need to have a better idea of what your system requirements are in order to better assist.

    Best Regards,
  • Thank you Robert.

    We need to deliver 75W into an 8Ω loudspeaker load (and, accordingly, 100W into 6Ω).

    My assumptions:

    • Extrapolation of your P vs PVDD curves (basically as expected given the FETs' Ron) gives ~36V developing the required power.
    • Understand that while that voltage may well pose dissipation issues with a lower impedance load,
    • this is a restricted application which will NOT be operated under a 6Ω load.

    Just want to make sure that we are not exposing anything else unseen here... thanks for looking into this.

    Another question - how does the 3245 actually differ from the 3251?

    If I can PM you, I'll can more information about our application pursuant to another question or two.

    Thank you again. 

  • Hi Bob,

    The TPA3245 is rated for a lower PVDD voltage than the TPA3251 and it has a lower power level than the TPA3251. These are the two main differences between the devices.

    So if you want to use 36V, I would strongly recommend using the TPA3251 instead since that PVDD rating is within the recommend voltage range.

    My email address is r-clifton(at)ti(dot)com, let me know if you have any other questions.

    Best Regards,