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    VRM Output cap ESR

    The output capacitor ESR is important in terms by bypassing the bulk of the output ripple and transients away from the CPU.

    I thought I would see what the ratio of ESR is to the CPU load (V/I) is used on motherboards. I calculated the ratio for two boards.

    1. A 1.5V 85W CPU = 26.7 milliohm the filter caps 6 x 3300u MBZ = 2 milliohm an ESR to Load ratio of 1: 13.35

    2. A 1.35V 65W CPU = 28 millohm the filter caps 9 x 820u 2.5V poly = 0.78 millohm (my current system)
    ESR to load ratio. 1:36

    Clearly the second board has a higher percentage of ripple flowing through the caps.
    Last edited by davmax; 03-12-2008, 12:57 AM.
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