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TLV320AIC3262 SPL driver short circuit detection

Akio Ito
Genius 3595 points
Other Parts Discussed in Thread: TLV320AIC3262

Hi,

Our customer output a signal from TLV320AIC3262 SPL driver in DAC gain 0dB,
just soon the sound stopped, and D7 bit of Sticky Flag Register 2 (B0_P0_R44) turned on.
When DAC gain was -4dB, it did not.
This seems to detect a short circuit of SPL driver.
Are there other factors to turn on this bit?
They want to know its detection level.

best regards,
Akio Ito

  • 0
    TI__Mastermind 46195 points

    Hello Ito-san,

    Please refer to:

    www.ti.com/.../slaa581.pdf

    The Class-D output is rated for a MIN of 7.2-ohm, so the output filters must be designed such that the impedance seen by the amplifier is close to this level at a minimum.

    If I remember correctly, the OCP threshold is close to 800mA per channel.

    Regards,

    J-

  • 0 in reply to J-
    Genius 3595 points

    J Arbona-san,

    Our customer sent me the current waveform measured by a electric current probe between terminals SPKLP and Loudspeaker.

    The upper waveform seemed to be detected overcurrent. The current is about 1000 mAp-p.

    The lower waveform is clipped by the maximum volume of Linux ALSA driver, but is not detected overcurrent. 
    The current is about 1150 mAp-p.

    A question of our customer is whether the threshold of 800mA has a factor of time.

    best regards,
    Akio Ito

  • 0 in reply to Akio Ito
    TI__Mastermind 46195 points
    Hi Ito-san,

    Please allow us to gather some information first. I will get back to you as soon as I can.

    Thanks,
    J-
  • 0 in reply to J-
    Genius 3595 points
    J Arbona-san,

    Thank you for suggestion of the cooperation.
    If some information is provided from the customer, I will report it immediately.

    best regards,
    Akio Ito
  • 0 in reply to Akio Ito
    TI__Mastermind 46195 points

    Hi Ito-san,

    The AIC3262 trip current MIN is 850mA device to device. Its purpose is to protect the device from overcurrent. From specification perspective, load should not be below 7.2-ohm (which for 5.5V supply corresponds to 0.76A).

    OCP trigger is based on instantaneous current.

    When measuring current, make sure it is measured before any filter caps and not at the load. This will tell you the current at the pin.

    Regards,

    J-

  • 0 in reply to J-
    Genius 3595 points
    J Arbona-san,

    I got an important fact from our customer.
    When the OCP happened, they had written incorrect value 0xC2 to a reserved register (b0_p1_r81).
    On the other hand, in case of Linux ALSA where OCP did not occur, they did not write it.

    Of course they don't want the description of the reserve register.
    But they want to know whether this can explain its phenomenon.

    best regards,
    Akio Ito
  • 0 in reply to Akio Ito
    TI__Mastermind 46195 points

    Hi Ito-san,

    Thanks. This is indeed an important fact from the customer.

    As I mentioned, the default OCP threshold MIN level is 850mA peak.

    But, if customer programs B0_P1_R81 = 0xC2, that will change the OCP threshold MIN level to 500mA peak. This correlates with the observation from the customer. So B0_P1_R81 must be 0x00, which is the default.

    Thanks,

    J-