From: Rick Brooks (firstname.lastname@example.org)
Date: Fri Nov 05 1999 - 18:48:15 PST
Has anybody ever tried 0508 caps (not 0805) with multiple trace/vias to the planes?
It seems like a better idea for low inductance, but I don't know about the cost or availability.
- Rick Brooks
At 04:59 PM 11/05/1999 -0800, you wrote:
>> Date: Fri, 05 Nov 1999 16:39:47 -0800
>> From: Howard Johnson <email@example.com>
>> If you want to achieve an even lower impedance, try smaller capacitors,
>> or go with some of the more advanced packages (for
>> example the new "IDT" package from AVX claims to
>> deliver an installed inductance of 0.1 nH per component.)
>> Best regards,
>> Dr. Howard Johnson
>Most of the inductance is not in the capacitor but is in the pads
>and vias to the power planes. Our studies show that the inductance
>in the capacitor itself is between .2 and .4 nH for 0805 capacitors,
>depending on the height. The mounting inductance usually ranges
>from 0.3 to 2 nH depending on the depth of the vias to the power
>planes and the spacing between vias.
>The cost of low inductance capacitors is not worth it unless you
>are going to commit substantial board area for multiple vias to
>the power planes and can tolerate the loss of wiring channels.
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