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LM4819: LM4819 Pop noise issue at power down.

Part Number: LM4819

Hi

My customer have the pop noise issue when power down timing.

Output waveforms and schematics are below, 

The condition2 is little bit improved the pop noise than conditon1.  However. customer have to decrease the pop noise more.

Could you please give me your advice for improvement method?

Condition1:  Ci=0.22uF, Ri=47kΩ, Cb=1uF

(Ch1:VDD(5V)  Ch3:Vo2+ Ch4:Vo1-  Math:Ch3-Ch4)

Condition2:  Ci=0.1uF, Ri=100kΩ, Cb=1uF

(Ch1:VDD(5V)  Ch3:Vo2+ Ch4:Vo1-  Math:Ch3-Ch4)

Schematics (same circuit in datasheet)

Thanks

Muk

  • I missed the attached file.

    Condition1:  Ci=0.22uF, Ri=47kΩ, Cb=1uF

    (Ch1:VDD(5V)  Ch3:Vo2+ Ch4:Vo1-  Math:Ch3-Ch4)

    Condition2:  Ci=0.1uF, Ri=100kΩ, Cb=1uF

    (Ch1:VDD(5V)  Ch3:Vo2+ Ch4:Vo1-  Math:Ch3-Ch4)

    Schematics (same circuit in datasheet)

  • In reply to Yusuke Mukuno:

    Hello Mukumo-san,

    You could decrease the input capacitor or could increase the bypass capacitor in order to reduce pop noise.
    You should take into account that the input capacitor value shouldn't be higher than necessary to meet the desired -3dB frequency and if the bypass capacitor is increased, turn-on time increases too.

    Best Regards
    José Luis Figueroa
    Audio Applications Engineer
  • In reply to José Luis:

    Hello Luis-san,

    Thank you for your reply. We will try to confirm your advice.

    Thanks
    Yusuke Mukuno
  • In reply to Yusuke Mukuno:

    Hi Luis-san,

    Customer try device shutdown before Vdd power down. They use SHUTDOWN pin. SHUTDOWN pin is active-high. In this case, the pop noise is improved.

    Shutdown pin is pulled up other 5V power supply. (Controled by MCU)

    At that time. It will become VDD pin voltage < Shutdown pin voltage .

    Is it no problem?

    Thanks

    Muk

  • In reply to Yusuke Mukuno:

    Hello Mukuno-san,

    It is always recommended setting the Vdd and shutdown voltage to the same voltage level in order to avoid any kind of problem.

    Best Regards
    José Luis Figueroa
    Audio Applications Engineer
  • In reply to José Luis:

    Thank you.

    I willl try to suggest pull-up to Vdd to customer.

    Muk