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AD9545/PCBZ: Why the 0.1uF capacitor is placed in front of the filter?

Category: Hardware
Product Number: AD9545

Hello,

I have a question about AD9545/PCBZ from our customer.
On the AD9545/PCB, the VDD pins are connected through 0.1uF capacitor, Z20x filter from VDD_DUT.
Usually, I think the 0.1uF capacitor is placed near the VDD pins, and the filter is placed on the front of the 0.1uF.
Why is the 0.1uF capacitor placed in front of the filter on the AD9545/PCB?

Best regards,

y_suzuki

  • HI,

    the ferrites are placed on the pins 10, 13, 19, 24, 27, which are the LDOs of the AD9545 outputs. The ferrites have been placed to minimize output to output coupling. Placing these ferrites as close as possible to the pins minimizes the output to output coupling.

    We recommend to use the ferrites from the evaluation board. Using different ferrites may compromise the stability of the LDOs.

    Petre

  • HI,

    Reading your message that somehow I cannot find anymore made me realized that indeed, I should have said that the pins 10, 13, 19, 24, 27 are supply inputs, that is are the inputs to internal LDOs that manage the AD9545 outputs. The ferrites have been placed to minimize the coupling between outputs and the inputs into the LDOs.

    Sorry for confusing you.

    Petre