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Original question:

LM4838: LM4838 amp out have click noise

LM4838: About shutdown operation and tantalum capacitor

Liu Yang
Expert 5915 points
Part Number: LM4838
Other Parts Discussed in Thread: LM4952,

Hi Team,

I am designing a circuit with the LM4952, and I have two questions.

1. About pop noise during shutdown operation
If the shutdown operation is turned OFF → ON or ON → OFF when there is no signal input, will a pop noise occur? (The circuit configuration assumes Figure 2 in the data sheet.)
Also, if it occurs, is there a way to reduce the pop noise?

2. About tantalum capacitors
Data sheet P.13 states that " Do not substitute a ceramic capacitor for the tantalum. Doing so may cause oscillation." Since the use of tantalum capacitors is prohibited, is there any way to replace tantalum capacitors? Although it is a separate device, the following inquiry states that it can be replaced by mounting a resistor in series with the ceramic converter.
https://e2e.ti.com/support/audio/f/6/p/701040/2597783?tisearch=e2e-sitesearch&keymatch=LM4952#2597783

With this device, the same problem can be solved by raising the ESR. Is there no problem in recognition? And what are the recommended values for the resistance in that case?

Beat Regards,
Tom Liu

  • 0
    TI__Guru* 95175 points

    Hi Liu,

    I'll add some comments on your questions below:

    1. As described in the data sheet, pop noise is affected by several factors, you must consider specially the bypass capacitor. Pop noise is essentially caused by mismatch between the input signals, during power up and power down the charge/discharge of the capacitors in the signal path can be affected by layout, device impedance and resistors.
    2. It is most likely the same applies for LM4952 than LM4838. Unfortunately these old legacy devices are very difficult to support as we do not have access to any evaluation board for it, you can anyways try by placing the ceramic cap and adding series resistance. Unfortunately the same as LM4838, we do not have a suggested resistance value for LM4952.

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