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TPA3255: TPA3244

Ken Obee
Prodigy 10 points
Part Number: TPA3255
Other Parts Discussed in Thread: TPA3251, TPA3245

Hi,

I am a hobbyist and I am planing to build a class D amp using TPA3245 or TPA3251. I am going to use in 8ohm floorstand speaker with 92dB sensitivity. I would like to run it in PBTL mode. However, I checked the datasheet that for PBTL mode, it mentioned to use 2-4ohm speakers. May I know is it not good to use 8ohm speaker for PBTL mode for both chips? Which chip better suit me?

Thanks

  • 0
    TI__Mastermind 27990 points
    Hi Ken,

    Using 8 ohm loads in PBTL is no issue with either part, there is just no power output advantage over using BTL with 8 ohm, since the part is limited to a 38V supply. You will have the thermal advantage of using 4 FETs to drive one speaker instead of 2 lowering the thermal stress per device/FET, or with a more robust cooling solution you could push the same power on two channels into 8 ohms with one device.

    Justin
  • 0
    TI__Intellectual 1840 points
    Hey Ken,

    Just to add, I was wondering if you had a specific output power you had in mind. Since the supply voltage is limited to 36V max for the TPA3251, a higher ohm speaker would demand more output voltage swing to achieve the same level of power through a lower ohm speaker. You can see from the datasheet that the max output power capability decreases with increase in speaker impedance.

    But this of course, is all subjective to what the designer wants in terms of typical or maximum output power. There is no issue using an 8 ohm speaker as long as your power requirements meets the allowed specifications.