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TPA2028D1: PWM Modulation Method

Sadanori Kato
Guru 36530 points
Part Number: TPA2028D1
Other Parts Discussed in Thread: TPA2026D2

Hi,

Could you please tell me the pwm modulation method(AD mode or BD mode or 1SPW mode) for TPA2028D1 ?

Best regards,
Kato

  • 0
    TI__Mastermind 20085 points
    Hello Kato-San,

    The PWM modulation method used by TPA2028D1 is BD modulation. In fact, the most TPA amplifiers use BD modulation.

    Best Regards
    José Luis Figueroa
    Audio Applications Engineer
  • 0 in reply to José Luis
    Guru 36530 points

    Hi José-san,

    Thank you for your reply.

    It seems that the pwm modulation method for TPA2028D1 isn't same with TPA2026D2 one when observing the single-ended output after the LC filter with the oscilloscope.
    Is my understanding correct that it is difference between the pwm modulation methods ?

    Best regards,
    Kato

  • 0 in reply to Sadanori Kato
    TI__Mastermind 20085 points
    Kato-san,

    Both devices use BD modulation, the differences between them is the speaker channels number and other features.

    Best Regards
    José Luis Figueroa
    Audio Applications Engineer
  • 0 in reply to José Luis
    Guru 36530 points

    Hi José-san,

    For TPA2028D1 a half wave rectified signal is output from each channel if inputting the 1kHz sine wave when observing the single-ended output after the LC filter with the oscilloscope.
    On the other hand, for TPA2026D2 a sine wave is output in the same condition.
    So, I understand that it is difference between the pwm modulation methods.

    Best regards,
    Kato

  • 0 in reply to Sadanori Kato
    TI__Mastermind 20085 points
    Hi Kato-san,

    Both devices use BD modulation, perhaps the problem could be the way how you make the measurement. You need to add a 30 kHz low-pass filter at the output in order to perform the measurement.

    Best Regards
    José Luis Figueroa
    Audio Applications Engineer
  • 0 in reply to José Luis
    Guru 36530 points

    Hi José-san,

    I evaluated TPA2028D1YZFEVM, so please see the following capture.
    As I mentioned above, a half wave rectified signal is output from each channel in TPA2028D1.
    * yellow : OUTP, blue : OUTM, red : OUTP - OUTM

    This phenomenon isn't issue, so I would like to tell you only that the single-ended output waveform for TPA2028D1 isn't same with TPA2026D2 one.

    Best regards,
    Kato

  • 0 in reply to Sadanori Kato
    TI__Mastermind 20085 points
    Hi Kato-san,

    That could be a problem with the LC filters. You can measure the devices before the LC filter in order to check their behavior, the output of a TI's Class-D amplifier is a PWM switching signal with a duty cycle that is modulated with an audio signal.

    Best Regards
    José Luis Figueroa
    Audio Applications Engineer
  • 0 in reply to José Luis
    Guru 36530 points

    Hi José-san,

    Judging from my evaluation results, I believe that TPA2028D1 adopts 1SPW mode as the pwm modulation method.
    So, you would replicate the same phenomenon if you also evaluate it.
    Please double-check if you are interested in this behavior.

    Best regards,
    Kato