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TPA3251: PWM mode and suitable LPF configulation

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

Hello,

Our customer try to design LPF of TPA3251 seeing Apps note slaa701a "Table 1. Class-D Filter Types and Their SE Equivalent Circuits" on page 8.

There are LPF configurations as Type-1 for AD mode, Type-2 for BD mode and Hybrid.  We know BD mode cannot accept Cbtl which placesd across +output and -output node.

In the case of TPA3251, no description of PWM mode on the datasheet.

We would like to confirm PWM mode of TPA3251 and suitable LPF type.

Our expectation is that its AD mode and all of LPF type can be used. Is it correct?

 

Regards,

Mochizuki

  • Hi  Mochizuki

        Our newer device all use BD modulation, it will reduce the high frequency components flows into the speaker, better for the EMI and efficiency. TPA3251 only use BD.

        Even in AD modulation, we still recommend to use the capacitor connected to GND. Because in realities, AD is not perfect differential. 

  • Hello,

    Thank you for the reply.

     We understood even AD mode D-amp, placed bypass cap between GND is better for lowering EMI.

    The other hand, attached waveform is TPA3251 PWM output waveform, we believe it is AD mode.

    In our knowledge, TPA3251 is the first generation of TPA32xx family device, TPA3245 and TPA3255 are younger generation device but it is employed AD mode modulator as described it on the datasheet.

    So, would you please check it out again about TPA3251 is using AD mode too.  And AD mode D-amp device can accept all of Type-1, Type-2 and Hybrid LPF configuration.

     

    Regards,

    Mochizuki

  • Hi  Mochizuki

     

    So, would you please check it out again about TPA3251 is using AD mode too.  And AD mode D-amp device can accept all of Type-1, Type-2 and Hybrid LPF configuration.

     

     

      You are correct, thank you.