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TPA3255: TPA3255 PBTL mode ，if use 2Ω speaker ， will turn into overcurrent limit protection immediately

Frank Peng
Intellectual 440 points
Part Number: TPA3255

Hi  !  

             It is need your help ,   the schematic as below , TPA3255  in  PBTL  mode ，if  use 2Ω speaker ， will turn into overcurrent limit protection  immediately .   Thanks  a lot  !

, 

  • 0
    TI__Guru 63710 points
    Frank,

    Are you using the EVM? Or your own board?

    Do you mean immediately once the amp is enabled? Or immediately once music starts playing?

    Is the speaker 2Ω nominal? Do you have the impedance curve of the speaker? Maybe the impedance of the speaker is going too low at a certain frequency.

    Regards,

    -Adam
  • 0 in reply to Adam Sidelsky
    Intellectual 440 points

    Hi ！   Adam 

            It is a  own board ,  the power supply is 51V , when use a 4Ω speaker , it  works good . I also try to use a  3Ω speaker,  when the current is 17A , will turn into overcurrent limit protection  immediately  .  It has not yet reached  600-W Mono into 2 Ω in PBTL Configuration . if  the schematic of TPA3255 need some change ?   Thanks a lot !

  • 0 in reply to Frank Peng
    TI__Guru 63710 points
    Frank,

    17A is correct for the highest OC trip point. Can you check if you see the Cycle-By-Cycle Current Control active when you approach 17A? If this is enabled, you will see the device skip some PWM pulses when you approach the 17A OC limit.

    What value resistor are you using for OC_ADJ? Can you send your output inductor datasheet?

    Can you try the board with a 2Ω dummy resistor load? My concern is that the speaker impedance is dropping too low at the higher output power and Over-current is protection is occurring.

    Regards,

    -Adam
  • 0 in reply to Adam Sidelsky
    Intellectual 440 points
    Hi ！ Adam
    The resistor for OC_ADJ is 22K， I try to use a 2Ω dummy resistor load, and is the same . the FAULT pin will be pull down . in PBTL mono mode ，the the highest OC ， it is 17 A or 34A ? Many thanks !
  • 0 in reply to Frank Peng
    TI__Guru 63710 points
    Frank,

    The OC is listed per output so they are each 17A. You may have an output LC filter problem. Can you share the specifications of your output Inductor and Capacitor?

    Regards,

    -Adam
  • 0 in reply to Adam Sidelsky
    TI__Guru 63710 points
    Frank,

    I am closing this thread, please reopen if you have more information or need more help.

    Regards,

    -Adam

    If I have answered your question please click the "This resolved my issue" button on this thread.