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LM4889: What is recommended bypass capacitor type and value for LM4889?

Part Number: LM4889

Hello guys,

One of my customers is consider using LM4889 for their new products.

They have the following questions. Could you please give me your reply for them?

Q1. What is recommended value and type of bypass capacitor placed between VDD and GND? Is capacitor type electrolytic capacitor or ceramic one? Is the value 1uF?

Q2. What is how to use for the minimum consumption current except shutdown mode?

Q3. Is there any way to improve noise immunity?

Your reply would be much appreciated.

Best regards,
Kazuya.

  • Hi Kazuya,

    1. The decoupling capacitors on VDD would depend on how well your supply is regulated. Usually a 10uF or 1uF acts as a local reservoir along with a small 0.1uF that helps to filter high frequency from the supply line. Ceramics are most commonly used although you may also use electrolytic for the bigger cap.
    2. There's no specific setup for low power consumption other than shutdown mode. Perhaps AC coupling the input to GND and leave the outputs floating could improve a bit the consumption when active, you may need to test this to see if it really makes a difference and seems more complicated than just controlling the Shutdown pin.
    3. Best practice is to place all decoupling capacitors as close as possible to the IC, including Bypass pin. Do not route the Bypass pin capacitor far from IC. Try to make a short path from input signal source so it doesn't pick up noise in the way to the amplifier. And make sure to have a good GND return path to the power supply in a start connection if possible, or make sure that GND returns from potentially noisy circuits is not passing through the amplifiers GND reference.

    Hopefully this helps with customer design, if there are any further specific questions please let us know.

    Best regards,
    -Ivan Salazar
    Applications Engineer