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TAS6422-Q1: Over current issue

Jonathan Geronga
Expert 7930 points
Part Number: TAS6422-Q1

Hi Team,

I would like to get some help for the situation of our customer below:

The customer used TAS6422-Q1 in their end product powered by 14.4V (battery voltage) with two 2 Ohm loudspeakers.

The problem was, on the full volume the second loudspeaker goes into overcurrent fault and disables itself.

It is always channel 2 and not channel1. They play mono sound files, so the sound level should be the same for both speakers.
If only plug in a loudspeaker to channel 1 everything works fine even on full volume.

Do you have any idea what might cause this? Or how to debug this?
Also according to the datasheet, the amplifier should run a diagnosis on the faulty channel and if it does not detect an error it should enable again? But according to their test the channel just goes to HI-Z. Should the software reenable the channel itself?

Let me know if you need more information.

Thanks!

Jonathan

  • 0
    TI__Genius 9530 points

    Jonathan,

    May you dump all the register when this problem happens. I need to find the root cause of OC reported.

    Dylan

  • 0 in reply to Dylan Yao
    Prodigy 200 points

    Hello Dylan,

    Jonathan put my support request here, so i will answer here:

    The strange thing is, that the overcurrent error only happesn if both laudspeakers are connected. If only one speaker is connected on either channel 1 or channel 2, it does not happen.

    If you need any more info, please tell me and i will try to acquire it.

    The requested register dump in the error state:

    [0x0]: 0x0
    [0x1]: 0x32
    [0x2]: 0x62
    [0x3]: 0x4
    [0x4]: 0x0
    [0x5]: 0xff
    [0x6]: 0xff
    [0x7]: 0xcf
    [0x8]: 0xcf
    [0x9]: 0x0
    [0xa]: 0x0
    [0xb]: 0x11
    [0xc]: 0x0
    [0xd]: 0x0
    [0xe]: 0x0
    [0xf]: 0x15
    [0x10]: 0x40
    [0x11]: 0x0
    [0x12]: 0xc
    [0x13]: 0x1c
    [0x14]: 0x0
    [0x15]: 0x0
    [0x16]: 0x0
    [0x17]: 0x0
    [0x18]: 0x0
    [0x19]: 0x0
    [0x1a]: 0x0
    [0x1b]: 0x0
    [0x1c]: 0x0
    [0x1d]: 0x0
    [0x1e]: 0x0
    [0x1f]: 0x0
    [0x20]: 0x0
    [0x21]: 0x88
    [0x22]: 0x1
    [0x23]: 0x14
    [0x24]: 0x3
    [0x25]: 0x0
    [0x26]: 0x40
    [0x27]: 0x60
    [0x28]: 0xa

  • 0 in reply to Dominik Wenger
    TI__Mastermind 19410 points

    Hi Dominik,

    From the registers value, CH2 has OC fault. And from 0x12 and 0x13 registers, CH1 and CH2 also were overtemperature.

    Can you add one fun on heat-sink to reduce the temperature firstly?

    We should make sure there is no OT fault firstly.

    Regards,

    Derek 

  • 0 in reply to Yanming Gong
    Prodigy 200 points

    Hello Derek.

    Yes, we saw the overtemperture error too.

    We tried to improve the heatsinking but the error still occoured. I will try to get a register dump with the improved heatsinking, but that will take a bit time, as it only really happens in the car.

    The strange thing is this only happens if two loudspeakers are connected and it is always channel 2. Also i cant really reproduce it on my bench and in the car it happens always after a few seconds on full volume.

  • 0 in reply to Dominik Wenger
    TI__Mastermind 19410 points

    Hi Dominik,

    Can you swap the CH1 and CH2 inductors and test again?

    I am afraid that the rate current of inductors will be reduced on high temperature case.

    Regards,

    Derek

  • 0 in reply to Yanming Gong
    Prodigy 200 points

    Hi Derek,

    The CH1 and CH2 inductors are the same type on this board ( FDSD0420-H-3R3M=P3, selected according to sloa242a.pdf). So i am not sure on how i would swap them.

    If temperature might be a problem for them, desoldering the CH2 inductors and swapping them with the CH1 inductors will not change their temperature based on location. And i cant really swap the traces going to them. The board is pretty thight at this location.

    But i will try to add extra heatsinking to the inductors and try again, and then report back.

    kind regards

    Dominik

  • 0 in reply to Dominik Wenger
    TI__Mastermind 19410 points

    Hi Dominik,

    Please make sure there is no OT fault firstly. I am afraid that OT lead to OC fault.

    Regards,

    Derek

  • 0 in reply to Yanming Gong
    Prodigy 200 points

    Hi Derek,

    i will try again to get a hold of the car with the module with improved cooling, so i can get the register dumps.But now before christmas everyone is very busy :-)

    In the mean time i found a temporary fix: If i reduce the gain setting to 7.6V peak, both loudspeakers work (but it is ofcourse not as loud).

    kind regards

    Dominik

  • 0 in reply to Dominik Wenger
    TI__Mastermind 19410 points

    Hi Dominik,

    Reduce the gain, it will also reduce the output power with same input signal level. 

    And the heat also will reduce with output power.

    Regards,

    Derek