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TPA3112D1: Class D amplifier for Mono system

Kai Nomiyama
Expert 5295 points
Part Number: TPA3112D1
Other Parts Discussed in Thread: TPA3126D2

Hi Audio team,

I have questions about class-D for following requirement.
Mono/Stereo: Mono
Input: Analog in
Output: BTL
PVDD: 8V
Power: 16~20W with 10% THD+N

Could you help below questions?
[Question 1]
Do you have any data that shows TPA3112D1 can output 16~20W with 10% THD+N from 8V, or how much TPA3112D1 can output with 10% THD+N from 8V?

[Question 2]
In addition, do you have any other recommended devices for above requirement?

[Question 3]
When I take a look at some datasheet like TPA3126D2/3128D2, these support PBTL.
However, these datasheet describe 10% THD+N maximum output power from 8V is 12W at 3RL.
TPA3126D2 figure 24.

From below calculation, possible output power seems to be 170W but why TPA3126D2/28D2 max output power is limited by 12W?
8V PBTL configuration is 32Vpbtl(22.6Vrms)
P=V^2/RL=170W

Regards,
Kai

  • 0
    TI__Mastermind 19080 points

    Hi Kai,

    Output power capability also depends on the speaker resistance. For example, with a 3Ohm speaker, 8V PVDD, the max output power without voltage clipping is (8V)^2/2/(3Ohm) = ~10.6 W. 

    You may need a 2Ohm speaker, clipping occurs when output power reaches 16W.

    Regards,

    Hao 

  • 0 in reply to Sam(MPAA) Zhang
    TI__Expert 5295 points

    Hi Hao,

    Sorry but I forgot to describe RL information.
    RL=4ohm
    Mono/Stereo: Mono
    Input: Analog in
    Output: BTL
    PVDD: 8V
    Power: 16~20W with 10% THD+N


    Is your configuration of following calculation SE?
    (8V)^2/2/(3Ohm) = ~10.6 W.

    I'm not very familiar with audio products but above figure 24 that I attached is PBTL configuration so actual voltage should be 8(SE) --> 16(BTL) --> 32(PBTL).
    When RL=4ohm(customer case), max output power without voltage clipping should be (32)^2/2/4=128W.

    I think my understanding has someting incorrect so please let me know how to calculate max output power with BTL/PBTL configuration?

    in addition, as you mentioned, don't we have any devices supporting customer requirement except using 2ohm speaker?

    Regards,
    Kai

  • 0 in reply to Kai Nomiyama
    TI__Mastermind 19080 points

    Hi Kai,

    In BTL, the Vpeak of output is PVDD. Output power capability for BTL is calculated as, PVDD^2/2/R. PBTL only have higher current capability than BTL. Problem for 8V PVDD is voltage clipping, while voltage clipping point is the same in PBTL.

    While for SE, the Vpeak of output is PVDD/2. Output power capability for BTL is calculated as, (PVDD/2)^2/2/R.

    Voltage clipping is a theoretical limitation here, with nothing to do with which device you use. If PVDD is limited to 8V, then I would recommend you to use a 2Ohm speaker.

    Thanks!

    Regards,

    Hao