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TAS5782M: Mono Mode ( Post-Filter PBTL )

Stefan Dreyer
Prodigy 110 points
Part Number: TAS5782M

Hello guys,

I want to implement a SW function, that the TAS5782M can be used either in Mono or Stereo mode.

For me, the information in the datasheet is ambiguous.

Here, it shows that SPK_INB+ and SPK_INB- are supposed to be grounded. Additionally, the post implies that this is a requirement to mono mode.

e2e.ti.com/.../tas5782m-asking-for-the-tas5782-mono-application

However, the datasheet doesn't state this. Moreover, it says that a mixture of two channels can be used in mono mode. If I for example set the input mixer to route 100% left audio input data to both output stages and 0% of the right audio input, I can create a mono signal as well.

Hence the question: Do I need to connect SPK_INB+ and SPK_INB- to GND in Mono mode or can I set the TAS5782M to mono mode purely in software?

Thanks and regard,
Stefan

  • 0
    TI__Mastermind 40280 points

    Hi Stefan

    Stefan Dreyer said:
    However, the datasheet doesn't state this. Moreover, it says that a mixture of two channels can be used in mono mode. If I for example set the input mixer to route 100% left audio input data to both output stages and 0% of the right audio input, I can create a mono signal as well.

    This function is supported, and they are realized at the DSP side, you could check PPC3 for the Input Mixer Function. After the Mixer, the device will actually only use Channel A for PBTL. So when signal comes to DAC side, actually only DAC_OUTA need to work. 

    Connect SPK_INB+/INB- to GND will help to reduce device's noise, and guarantee the performance. So we still suggest you to make this change. You could try to use the way according to your system requirement, the performance maybe affected a little, and can't be fully guaranteed by us. 

  • 0 in reply to Shadow He
    Prodigy 110 points

    Hi Shadow He,

    Thanks for the reply. So if I want to implement this in SW, I need 2 transistors to pull  SPK_INB+/- to GND (as I dont want jumpers). Is it suitable to use 2x 10kOhm resistors and simple NPN's to do that? The 10k will connect DAC_OUTB with 2µ2 to GND; hence the load on that pin is limited.

    Can you confirm this approach?

  • 0 in reply to Stefan Dreyer
    TI__Mastermind 40280 points

    Hi Stefan

       For SPK_INB+/-, better no need for the 10K resistor, only use NPN pull to GND. And for DAC_OUTB, could consider add one 10K resistor to GND.