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Original question:

LM4871: LM4871LD PAD connect to GND?

LM4871： LM4871 output is abnormal

QI Jepson
Intellectual 320 points

Part Number: LM4871

Hello, my client applied for a 50pcs sample and found that there was no output of 4pcs when the application was designed.

The following is a schematic diagram of the customer's design.

The design needs to push the 8Ω 2W speaker，Is this design reasonable?

What are the reasons for the chip failure, you can tell the customer to evade in advance.

  • 0
    TI__Guru** 114395 points
    Hi Jepson,

    Perhaps some IC's are damaged due to overloading.
    2W into 8Ω is too high for device spec. In the table at the top of page 4 from data sheet, it is shown that max for 8Ω is 1.5W. 2W is possible when using 4Ω or 3Ω load.
    In addition, what package is customer using? Since customer needs to operate near to the device limits, I would recommend to use LM4871LD and solder the exposed pad below the IC to a big GND plane for heat sinking purposes.

    Best regards,
    -Ivan Salazar
    Applications Engineer - Low Power Audio & Actuators
  • 0 in reply to Ivan Salazar
    Intellectual 320 points
    I also saw a maximum support of 1.5W output with a load of 8Ω. That is to say, although the load specification is 8 Ω 2W, only 1.5W of power is obtained after accessing the audio amplifier. At this time, the LM4871 is operating at full power, and it may cause chip damage after working for a long time. Is this correct?The customer chose the LM4871M. If the LM4871LD is selected and the thermal pad is added at the bottom, can this problem be avoided?
  • 0 in reply to QI Jepson
    TI__Guru** 114395 points
    Jepson,

    Continuous operation at device limit specification could cause damage.
    Changing to LM4871LD could help as the exposed pad would improve device dissipation during high power demands.
    They could first try to perform the test at lower output levels to verify if damage is caused due to excessive output power.

    Best regards,
    -Ivan Salazar
    Applications Engineer - Low Power Audio & Actuators