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TPA3244: PBTL mode configuration without jumpers

Stephen Dittmann
Prodigy 80 points
Part Number: TPA3244

Hi,

We're looking to use the TPA3244.  We want to have the ability to control the TPA3244 into PBTL from our MCU, so that we can eliminate the need for users to set/remove jumpers.  We are aware that the output wiring will be different between the 2 configurations and that does require user intervention.

The TPA3244 has Mode pins M1 and M2.  These denote the mode that the TPA3244 will power up in:

2xBTL, 2.1, PBTL, 4xSE

We find it curious that for PBTL mode the Input Pins INPUT_C and INPUT_D must also be connected to ground. 

We're wondering if this is actually a requirement for configuring the amplifier into PBTL mode, or perhaps it is simply to prevent/reduce noise.

Can anyone shed light on this?

Has anyone had success using a pair of mosfets to pull these pins to ground?  Besides a mechanical relay, are there any other solutions that are perhaps more elegant?

Looking forward to hearing your solutions.

Thanks in advance for any and all input.

  • 0
    TI__Mastermind 27380 points
    Hi Stephen,

    Can you give a little more information on your system? You mentioned that you will be using PBTL and another mode. What is the other mode that you want to configure?

    Best Regards,
    Robert
  • 0 in reply to Robert Clifton56
    Prodigy 80 points
    Thank you Robert for your response and interest in my question.

    We are planning to switch between 2 channel BTL and mono PBTL (paralleled after LC filter).
    I cannot offer much detail in the way of schematics as I have not started these yet. However, please reference Page 30: 10.3 Typical Application, Differential (2N), PBTL (Outputs Paralleled after LC filter) of the TPA3244 datasheet.
    In this application, TI has tied the inputs C and D to ground. Obviously these cannot be tied to ground in my application because I will need these so that I can drive the second channel in BTL mode. Therein lies my original question.

    Our device has power and audio in, and 4 speaker outputs. BTL and PBTL mode is configurable in software as a user option.
    The MCU will handle powering up the Amplifier in the respective mode.
    The user is responsible for connecting speakers to the outputs. This process includes paralleling the outputs after the LC filter.

    Thanks,
    Stephen
  • 0 in reply to Stephen Dittmann
    TI__Mastermind 27380 points
    Hi Stephen,

    2 channel BTL would make switching between one mode to the other a little trickier. Like you suspected, INC and IND need to be tied to ground in PBTL mode to prevent noise and stability issues that can be caused by leaving them floating.

    That said I don't see the problem with using mosfets to pull the inputs to ground. Please note that whatever type of switches you use for pulling INC and IND to ground, you will want to keep the it close to the amplifier for stability purposes.

    Regards,
    Robert
  • 0 in reply to Robert Clifton56
    Prodigy 80 points

    Thank you Robert for your feedback.

    We are going to proceed by using mosfets to pulldown INPUT_C and INPUT_D.

    I will update the forum with the outcome (hopefully it is a celebration of success).

    Thanks,

    Stephen

  • 0 in reply to Stephen Dittmann
    TI__Mastermind 27380 points
    Hi Stephen,

    Don't forget to also adjust M2 pin as well.

    I look forward to hearing about your success!

    Best Regards,
    Robert