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LMK04832-SP: VCC Clock Decoupling

David Wyatt
Prodigy 10 points

Part Number: LMK04832-SP

What is the recommended decoupling capacitors and their values after the ferrite for LMK04832-SP when the regulator is not on the same CCA as the device for the clock outputs such as Vcc2_cg1, etc?  Their are multiple caps on the eval board and it appears that all are DNI except for 1uF.  Do we need an additional larger value capacitor such as 8.2uF?  I say 8.2uF because we do not want to use a higher value capacitor that would require the size to increase.   It appears that there is a 10uF cap that is DNI for those type of outputs on the eval board.  Do you recommend the additon of other smaller value capacitors as well on those nets (they are DNI as well on the eval board)?  If clocks are powered down for a particular section, do we need decoupling capacitors and if we do can they be less than equal to 1uF?

  • 0
    TI__Guru** 118990 points

    Hi David,

    For Vccx_CGx supply pins, the 1µF capacitors are used to filter low frequency noise from SYSREF clocks. We think 1µF is good enough, the 10µF capacitor in the eval board is place holder for evaluation. These supply pins have internal small capacitors for high frequency SDCLK clocks filtering, no external small capacitors are required.