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TAS2505: Speaker output seems to get disabled when trying to configure AINL/R through Speaker (No sound)

Sohran Eliassi
Prodigy 20 points
Part Number: TAS2505

Hi, 

I am trying to configure the TAS2505 amplifier according to the 4.0.9 setup example (slau472 Application Note.pdf), but the output on the speakers do not have any PWM-output (Square wave), instead there is only a small DC-voltage (approximately 1V). You cannot hear any sound.

I am using SPI to write setup commands to the necessary registers, the Communication is working because I have read the registers afterwards and they have the correct values that i set them up too. HOWEVER, when reading the SPK register (0x2D page 1) it usually returns 0, even though i have set it up to Power the SPK by sending the value 0x02 to the register. Also, when i try to Power it up again by sending the value 0x02, you here a "clicking sound", seems like it is trying to Power up but gets disabled directly. I measured the output, there is only a small DC-voltage, no Square wave. I have tried configuring the amplifier on two devices, same result. 

ONE IMPORTANT THING, I have used the same configuration code on the TAS2505EVM and the sound is working on the evaluation card - you can hear sound from the speaker output. 

On our design we have SPKVDD = 5V, IOVDD 3.3V. 

I would appreciate some help and advice.

Kind regards,
Sohran

  • 0
    TI__Guru** 108715 points
    Hi Sohran,

    Perhaps the output is triggering its protection thus the output is disabled and the register is back to 0. Could you share schematic/layout of the output? If you have placed a filter at the output you should take care that the load impedance (filter+speaker) is at least 4-ohm and also that the cutoff frequency is below the Class-D switching frequency by half or more (Nyquist)

    Best regards,
    -Ivan Salazar
    Applications Engineer - Low Power Audio & Actuator
  • 0 in reply to Ivan Salazar
    Prodigy 20 points

    Hi Ivan,

    Unfortunately i can´t share the layout here since the forum is public. We do have a EMI-filter at the output but the filter doesn´t seem to be problematic because we tried connecting the SPK-output from the EVM through the filter of our design/layout and it worked - we got sound out.

    Also, the load impedance is atleast 4Ohm, just the speaker itself is at 4Ohm and working on the EVM-board so it should work on our design as well I guess.

    The only major difference in our design compared to the EVM-design is that we have connected the LDO_SEL pin to a 3.3V supply instead of a 5V supply (SPKVDD). In the data sheet they mension that LDO_SEL can be connected to SPKVDD, but is it a must? Or can LDO_SEL be connected to Another supply and one that has lower voltage than the SPKVDD? I mean, the LDO does get enabled and it generates an output voltage of 1.8V (AVDD pin)

  • 0 in reply to Sohran Eliassi
    TI__Guru** 108715 points
    LDO_SEL pin can be connected to a different supply than SPKVDD, as long as it is equal or above IOVDD.

    This post was handled offline.
    We're following up through email.

    Best regards,
    -Ivan Salazar
    Applications Engineer - Low Power Audio & Actuator