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PCA9554A: Bypass capacitor value

James Kim6
Prodigy 60 points
Part Number: PCA9554A
Other Parts Discussed in Thread: PCA9544A, , TCA9554A, TCA9544A

Hi,

I'm designing with a PCA9544A and can't find a application diagram of bypass cap value. My VCC is 3.3V. 

Could you recommend a cap value?

Regards,

James

  • 0
    TI__Guru 62910 points
    Hi James,

    A good value to use for the supply decoupling capacitance would be 100 nF.

    By the way, if this is a new design I recommend considering the TCA9554A instead. It has the same pin out and functionality of PCA9554A, but with some design improvements made.

    Please let me know if you have any further questions.

    Regards,
    Max
  • 0 in reply to Max Robertson
    Prodigy 60 points

    Hi Quote,

    Thanks for the cap value. TCA9554A is not a pin compatible to PCA9554A. PCA9554A has more pins of INT0-INT3.

    But we are not using INT0-INT3 so I'll design with TCA9554A. I want to confirm that TCA9554A can use same value of bypass cap 100nF.

    Regards,

    James

  • 0 in reply to James Kim6
    TI__Guru 62910 points
    Hi James,

    These part numbers are all similar and so it can get a little confusing. I just wanted to confirm:

    PCA9544A has the INT0-INT3 pins. TCA9544A is a pin-to-pin replacement.

    PCA9554A has only a single INT pin. TCA9554A is a pin-to-pin replacement.

    All four devices can use a decoupling capacitance of 100 nF. Note that the PCA devices will have some restrictions on the power supply ramp rate, though, as documented in the "power-on reset errata" sections of their respective datasheets. If these devices are used, you should make sure that the power regulator is able to provide correct ramp rates with the decoupling capacitance value selected.

    Max