Separate noise from STEP-UP CONVERTER

Discussion in 'General Electronics Chat' started by Vindhyachal Takniki, Feb 4, 2015.

  1. Vindhyachal Takniki

    Thread Starter Member

    Nov 3, 2014
    1. I have to make 5V from single Li-ion cell, whose voltage can vary from 2.7V to 4.2V.
    My current need at 5V is 400mA (max)

    2. I have selected TI's TPS81256 for this application. This is meant for my application.
    Just one output capacitor required, & thats it.

    3. TPS81256 works at 4Mhz. So it generate noise & it can effect my circuit as it has lots of analog cicuit.

    4. What value of decoupling capacitor I should use to filter this high frequency noise?

    5. Xc = 1/2*pi*f*c
    So I need Xc to be infinite for low freq & zero for high freq (ideally for bypass caps)
    So I think using 4.7uF, 10uF & 0.1uF in parallel will be sufficient?
  2. crutschow


    Mar 14, 2008
    Whether it's sufficient or not depends upon the circuit layout and grounding (do you have a ground plane?), and the sensitivity of your circuit.
    If that's not adequate you may need to add an inductor in front of the decoupling caps to provide more filtering.