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LM48511: failure of LM48511

Gary Guo
Prodigy 240 points
Part Number: LM48511

Hi Audio Folks,

        One of our customer used the LM48511, and found the device is easy damaged. and the output power is 4W when the load is about 4ohm. Power supply is 4.5V. and we also measured the boost voltage is about 7.2V. 

       the customer tested about 30pcs and do warm experiment test about 24 hours. and found there were 3-5 pcs damaged. and we also do the FA test. here is the test report. 

    so, it shows it has EOS damaged in Pin 8 and Pin12 . and the Pin 8 and Pin12 are the output pins.so the customer wonder to know how it cause this problem. by over-temperature or over-voltage? because the customer want to avoid this issue before mass production.

   so do you have and comments for this issues? or is there anything else we need to be noticed?  it's really urgent for us now. Thanks in advance.

   

  • 0
    TI__Mastermind 20085 points
    Hi Gary,

    I am not sure what is going on. I have a couple of questions.
    What is the FA conclusion? and, Do you know what is the power dissipation value of the device?

    Best Regards
    José Luis Figueroa
    Audio Applications Engineer
  • 0 in reply to José Luis
    Guru 36490 points

    Hi Gary-san,

    Excuse me for cutting in.

    It seems that LM48511 has only the thermal overload protection as the following post.
    The power consumption(Pd) increases and the efficiency for the integrated boost converter decreases if the power supply voltage(VDD) is less than 4.5V, then the output fets maybe be damaged as LM48511 doesn't have the overcurrent protection.
    For instance, please try to change VDD from 4.5V to 5V and decrease the PV1 voltage setting.

    https://e2e.ti.com/support/amplifiers/audio_amplifiers/f/6/t/560123

    Best regards,
    Kato

  • 0 in reply to José Luis
    TI__Prodigy 240 points
    Hi Jose,
    Thanks for your response. The conclusion of FA shows it damaged by Electrical Overstress. But we need to know the root reason behind it. we didn't measure the power dissipation. but what we know is the output power is about 3W to 4W. and the boost voltage is about 7.2V. after that the customer changed their PCB and improved the heat dissipation. finally found the failure rate decrease a lot. so we wonder to know does it relate with over-temperature or not.
  • 0 in reply to Sadanori Kato
    TI__Prodigy 240 points
    Hi Kato,
    thanks for your help, based on your comments. but the customer used the battery as it's power supply. so the input power is about 3.8V to 4.3V. we couldn't make it up to 5V. but the customer changed the heat dissipation and found the failure rate decrease a lot. does it means is caused by over-heat? and how did it damage the high side MOS-FET?
  • 0 in reply to José Luis
    TI__Prodigy 240 points

    M1_MB_P1 _ 17 AUDIO Interface.pdfHi Jose,

          I have attached the Schematic for your reference.

  • 0 in reply to Gary Guo
    Guru 36490 points

    Hi Gary-san,

    I think that the high side mosfet maybe is damaged due to the high current, in addition, the peaking current for the VDD power supply rail which is more than 2500mA flows with the 4ohm load.
    For instance, please try to change PV1 from 7.2V to approximately 6V if you cannot change VDD from 4.5V to 5V, but I have not verified it in detail.

    Best regards,
    Kato

  • 0 in reply to Gary Guo
    TI__Mastermind 20085 points
    Hi Gary,

    The schematic seems to be right.
    I think the problem is related to the capacity of the device to dissipate the power. As you mentioned when the customer changed the heat dissipation the failure rate decreased. This device needs a very good thermal dissipate to avoid over-temperature problems.

    Best Regards
    José Luis Figueroa
    Audio Applications Engineer