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TPA3111D1: About TPA3111D1 Audio Amplifiers

user3685640
Prodigy 70 points
Part Number: TPA3111D1
Other Parts Discussed in Thread: TPA3112D1,
Hello,

I am an electrical engineer from a Japanese company, who is manufacturing home-use electronic therapy devices. We use your amp in our product and just have a problelm we cannot solve by ourselves so please help.

Kindly see the attached for the details of my inquiry.
 
Looking forward to hearing from you.
 
Thank you,
 
Hiroki Akiyama
Senior Electrical Engineer
Marutakatechno Co., Ltd.
 
  • 0
    TI__Mastermind 24835 points
    Hi Akiyama-san,
    Looks like the FAULT is triggered. It could be OC, OT or DC. The issue only occurs with input signal applied, right? Does the issue occurs on all of the your board or only some of them(how much is the percentage)? Could you please try to use 0.1uF instead of 1uF input caps for the AMP to see if there is any improvement? The OC THR on TPA3111D1 is around 8~9A and it could vary from part to part. Make sure the output current is below this THR. And also make sure the temperature on the board is far less than 150C to avoid the OT fault.
    Please show me the SCH, it could be helpful for our debug work.
    Best regards,
    Shawn Zheng
  • 0 in reply to Shawn Zheng
    Guru 36490 points

    Hi Shawn-san,

    According to the following post, OC protection occurs when the output peak current is approximately over 4A.
    In addition, OT protection is NOT reported on the /FAULT pin and DC protection requires power supply recycle to clear the fault.
    So, I believe that the possibility that TPA3111D1 detects OC protection is high only when /FAULT pin is asserted to low.

    TPA3111D1, TPA3112D1 over current protection threshold
    https://e2e.ti.com/support/amplifiers/audio_amplifiers/f/6/t/169837


    Akiyama-san,

    The inductor may be saturating if the current rating of the inductor(33uH) is incorrect.
    So, could you please share the inductor part number which you are using ?

    Best regards,
    Kato

  • 0 in reply to Sadanori Kato
    TI__Mastermind 24835 points
    Hi Akiyama-san,
    I'm closing this question, please feel free to post in the forum if you have any other question.
    Best regards,
    Shawn Zheng
  • 0 in reply to Shawn Zheng
    Prodigy 70 points

    Hi Shawn-san,

    The issue only occurs with input signal applied, right? : Yes
    Does the issue occurs on all of the your board or only some of them(how much is the percentage)?: It is actually a part of them yet.

    I tried using 0.1uF input caps for the AMP as advised but could not see any improvement. I have measured the output current. Please kindly see the attached file and advise me if it should be judged as OC. Could you also tell me the pulse width for this OC THR of 8-9A? Kato san mentioned that OC protection occurs when output peak current is over approx 4A. What is the correct OC THR? I think the temperature of the board is not a problem and far less than 150C as I could touch it by hand.

    Thank you,

    Akiyama 

    Waveform when sound is issued.pdf

  • 0 in reply to Sadanori Kato
    Prodigy 70 points
    Hi Kato san,


    The part number of the inductor is SLF6028T-330MR69-PF(TDK).

    I have replaced the inductor to B952AS-H-330M(MURATA) and the problem does not occur any more.
    Wonder if that means the original one was saturated as you pointed out?



    Thank you,　



    Akiyama
  • 0 in reply to user3685640
    TI__Mastermind 24835 points
    Hi Akiyama-san,
    The OC THR on the TPA3111D1-Q1 is around 8A, and there is some variation for it from part to part and under different temperature. I think the 4A data is for one channel(BTL mode), while actually TPA3111D1 is a mono output amp(PBTL mode).
    I find the original inductor has very low rated current, and this makes the AMP outputs drive the 1uF large caps directly when the output current exceeds the inductor rated current and the inductor becomes saturated. The charging on the 1uF capacitors absort large current from AMP output and OC Fault is triggered. While the Murata inductors have higher rated current to avoid OC Fault. Please make sure the max output current is below the inductor rated current and reserve enough margin.
    Best regards,
    Shawn Zheng
  • 0 in reply to Shawn Zheng
    Guru 36490 points

    Hi Akiyama-san,

    Thank you for the information.

    As Shawn-san mentioned, the original inductor has very low rated current, so I believe that the root cause for this issue is the inductor saturation.

    Best regards,
    Kato

  • 0 in reply to Shawn Zheng
    Prodigy 70 points
    Thanks for your reply, Shawn san.

    Will get the inductor and see that. Could I have your further advice if there is anything I am not sure about the outcome? I understand OC THR is around 8A but what about the pulse duration?

    Thank you,

    Akiyama
  • 0 in reply to Sadanori Kato
    Prodigy 70 points
    Appreciate your advice, Kato san.

    Akiyama
  • 0 in reply to user3685640
    TI__Mastermind 24835 points
    Hi Akiyama-san,
    What do you mean by the pulse duration please? When the output current exceed the OC THR, the FAULT pin is driven to Low and the output is shut down, then the output current falls.
    Best regards,
    Shawn Zheng
  • 0 in reply to Shawn Zheng
    Prodigy 70 points
    I mean what is the time (sec) of this 8A OC THR?

    Thank you,

    Akiyama
  • 0 in reply to user3685640
    TI__Mastermind 24835 points
    Hi Akiyama-san,
    Thank you for the explanation. The delay between exceeding OC THR and shuting down the output is ~100ns inside the amp device.
    Best regards,
    Shawn Zheng
  • 0 in reply to Shawn Zheng
    Guru 36490 points

    Hi Akiyama-san,

    Please note that the output MOSFET may be damaged before detecting the OC when testing the ground fault if the rated current of inductor is extremely lower than the OC THR.

    Best regards,
    Kato