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TAS5756M: Mono PBTL without hybrilFlow use

Jeremy Tarantino
Prodigy 50 points
Part Number: TAS5756M
Other Parts Discussed in Thread: TAS5760M

Hello !

Firstable I want to apologize for my English ^^

Then, let's go for my interrogations :

I just bought an audio amplifier board for my raspberry PI, the main device of this board is TAS5756M.

The board manufacturer says that not any hybrid flow is used. So I suppose that the main board drive the component like a simple "DAC" by I2S.

Considering this, if I want to use the output in PBTL configuration, what am I supposed to manage on the DAC input signals ? I mean, if I make that both channel input signals are the same, what can prevent me from bridge output in PBTL configuration ? I don't see in the component datasheet any hardware configuration (by pull-up or pull-down or something else) to switch from BTL to/from PBTL. For example I don't find configuration pin like on the TAS5760M OR TPA3136.

I suppose there is a bit in an internal register configuration to "allow" PBTL mode, but I did not find in the datasheet which register has to be modify...

Thanks a lot for your answers,

Best Regards,

Jeremy

  • 0
    TI__Guru 52115 points

    Hi Jeremy,

    If you want the TAS5756M to work in the PBTL mode, please follow the reference schematic on Page 67 of TAS5756M datasheet to design your system.

    Andy

  • 0 in reply to Andy Liu (BMS)
    Prodigy 50 points

    Hi Andy,

    Thanks, I did not notice the difference between BTL and PBTL at DAC_OUTB and SPK_INB+/- level

    Can you just confirm me two other things :

    - Firstable, it's show page 58 that two filtering configuration are possible at spk_out level, can you just confirm me that post filter configuration is the same than BTL output filter configuration like page 63 ? I just have, at output connector level, to short outA+ with Out A- and OutB+ with OuB- and plug my speaker in PBTL like the schematic.

    -Then, if I modify the circuit to tie SPK_OUTB+ and SPK_OUTB- to PGND and pull down the DAC output like Page 67, I really don't have to make other register configuration for make the component works correctly in PBTL mode ? This sounds really weird to me, I do not understand how the H-bridge output can manage this output wiring without internal configuration, that why I just want to be sure

    Thanks a lot for your answer,

    Jeremy

  • 0 in reply to Jeremy Tarantino
    Prodigy 50 points
    OK, I think I will answer to my second question : I was reasonning in classic AD Modulation, I'm not really familiar with BD modulation, but it seems that this is the reason why output is not stressed by PBTL configuration, am I right ?
  • 0 in reply to Jeremy Tarantino
    Prodigy 50 points
    But I still have a question...
    I found this application report : SLAA701A
    If I compare figures 1 and 2 to the TAS5756M, the output configuration is different, I mean :
    - in the TAS5756M in PBTL, SPK_OUTA+ and SPK_OUTA- are shorted together and SPK_OUTB+ and SPK_OUTB- are shorted together
    - in this Application note, it seems that SPK_OUTA+ and SPK_OUTB+ are shorted together and SPK_OUTA- and SPK_OUTB- are shorted together

    Thanks a lot for your answer,

    Jeremy
  • 0 in reply to Jeremy Tarantino
    TI__Guru 52115 points
    Hi Jeremy,

    See my comments below.
    - Firstable, it's show page 58 that two filtering configuration are possible at spk_out level, can you just confirm me that post filter configuration is the same than BTL output filter configuration like page 63 ? I just have, at output connector level, to short outA+ with Out A- and OutB+ with OuB- and plug my speaker in PBTL like the schematic.
    Andy: Yes.

    -Then, if I modify the circuit to tie SPK_OUTB+ and SPK_OUTB- to PGND and pull down the DAC output like Page 67, I really don't have to make other register configuration for make the component works correctly in PBTL mode ? This sounds really weird to me, I do not understand how the H-bridge output can manage this output wiring without internal configuration, that why I just want to be sure
    Andy: No. The TAS5756M will be configured in MONO/PBTL when SPK_INB+ and SPK_INB- are connected directly to GND (without capacitors) during power-up. In mono mode, the right DAC channel, DAC_OUTA, is used as input for the speaker amplifier.

    Andy
  • 0 in reply to Andy Liu (BMS)
    Prodigy 50 points
    OK !!!
    I understand better how this can work !

    I'm really not familiar with this kind of component, I'm electronics engineer, but in space application, whe are really not used to using "smart" devices... :o)

    Thanks a lot Andy for your help, now, I have to play with my soldering iron and tweak this board