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TAS2521EVM: Speaker output disabled automatically

Eric Szaleniec
Prodigy 40 points

Part Number: TAS2521EVM

Hello there,

I'm using the EVM with a 4-ohms speaker,

I'm driving the board with different wav files (pure sine, white noise, simple bell, and a human spoken sentence), 

I'm measuring the acoustic levels.

Setup = 24 dB amplifier, -10 dB driver, DAC adjusted from -30 to +5 dB.

I can reach a max 95dBa with a 1kHz sinewave, when DAC=+5.

The output sustains the white noise wave at DAC=+5, producing 87dBa.

The output sustains the bell wave at DAC=+5, producing 90dBa.

When it comes to the human voice (only 2 simple words in the sentence),  I cannot go above DAC=-5 (80 dBa), the output is muted randomly (P0/R46/D7=0).

Any hint how to solve this problem?

Thanks.

  • 0
    Genius 3295 points
    Are you certain that there are not any high frequency transients in the waveform that are clipping and muting the device?

    Mike Tripoli
  • 0
    TI__Guru* 95225 points
    Hi Eric,

    Welcome to e2e.
    What output are you using? You mention 4-ohm speaker which makes me think you're using Class-D output. But then you mention P0/R46/D7 when the output is muted, this register is overcurrent flag for HPOUT.
    Do you have some scope captures of the output signal when it fails?
    The high frequency transients suggestion from Mike is also a good thing to look for.

    Best regards,
    -Ivan Salazar
    Applications Engineer - Low Power Audio & Actuators
  • 0 in reply to Mike Tripoli
    Prodigy 40 points

    Hello Mike,

    I have checked the audio file with Audacity, nothing to report.

    I have also crossfaded the transients (start/end of words) + LPF the entire file, no change.

    Eric

    (see next answer as well)

  • 0 in reply to Ivan Salazar
    Prodigy 40 points
    Ivan,
    my mistake, I messed up with the registers... and class-D output indeed (no use of AIN nor HP).

    I meant bit 1 of P1/R45 is cleared automatically (0=speaker down), by just setting it to 1 again I get the audio back until it is again cleared.

    Speaker is VISATON FR7: www.visaton.de/.../fr-7-4-ohm

    I have changed the speaker from FR7 (4 ohms) to its friend FR7S (8 ohms), no problem this time.
    I have changed the speaker to K64WP (8 ohms), no problem either.
    I have changed the speaker to FR58 (4 ohms), no problem either.

    Funny thing, if instead of screwing the SPKP wire in the connector, I just hold the wire and touch the screw at the top, then the output is fine (no auto mute).

    What do you suggest as filter on the differential output? maybe some speakers are too sensitive to the direct fast class-D outputs at high dBa levels?

    Thanks for your help.
  • 0 in reply to Eric Szaleniec
    TI__Guru* 95225 points

    Eric,

    You can take a look at the recommended filter values from the following Application Note: http://www.ti.com/lit/an/slaa701a/slaa701a.pdf
    Also you could consider using the recommended filter values from TAS2552/TAS2560:

    Description Specification MIN TYP MAX UNIT
    EMI Filter Inductors Impedance at 100MHz 120 Ω
    DC Resistance 0.095 Ω
    DC Current 1.5 A
    Size 402 EIA
    EMI Filter Capacitors Capacitance 1 nF

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

  • 0 in reply to Ivan Salazar
    Prodigy 40 points

    Ivan,

    thank you for the App Note, I'll manage from here.

    Eric