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LM358: LM358

Toshihiro Watanabe
Genius 10235 points
Part Number: LM358

Hello,

The customer wants to know how far bypass capacitor can be apart form IC. Would you advice it?

Best regards,

Toshihiro Watababe

  • 0
    TI__Mastermind 30600 points
    Hi Toshihiro-san,

    There isn't a set threshold for the decoupling capacitors. We recommend that they be placed as close to the device as possible. The closer the decoupling capacitors are to the IC, the more effective they will be. Section 12 in the datasheet details the layout guidelines and discusses this topic. It is most important to choose a low ESR cap and to have a low inductance connection between the cap and the power supply pin.

    Hope that helps,
    Paul
  • 0
    Guru 140200 points

    Hi Toshihiro,

    consider the decoupling cap as part of the chip. As Paul already mentioned, the decoupling cap should sit directly at the supply pin. It's best to have the other side of decoupling capacitor being connected to a solid ground plane, to which the supply ground and signal ground of LM328 is connected, too.

    Of course, it depends on the actual application and chip how important it is to have the decoupling cap sitting next to the chip. Some applications have a single decoupling cap for a group of amplifiers and work satisfactorily. Others need sophisticated parallel combinations of several decoupling caps at each chip to make the circuit work. But why taking the risk of having the decoupling cap too far away from the chip? Just place it always close to the chip and everything is fine.

    A standard decoupling capacitance of 100nF for each chip and supply line is sufficient for the very most cases.

    Kai