Re: [SI-LIST] : damping resistors ??

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From: Bo (bo_pfc@yahoo.com)
Date: Mon Feb 19 2001 - 13:32:31 PST


Stuart,

The need for series dumping resistors will depend on the drivers that you are
using. I can bet that SDRAMS you have used/seen before were not the same ones
you will be using in your current design. If you spend a little bit of time
doing simulations you will probably notice if in your case the damping
resistors are overkill or not. If you provide more details with respect what
drivers you are using in your design for each device and more details of your
design(e.g. trace lengths, rise/fall times of your signal, etc) someone reading
this mailing list might be able to help you more.

Regrads,
Bo

--- Stuart Adams <sja@brightstareng.com> wrote:
>
> Anyone have some rules of thumb when to use or not use
> series damping resistors ??
>
> I am reviewing a design (CPU + ASIC + SDRAM) and they have
> used series damping resistors on all the data and address busses
> (even for short point to point unidirectional busses)
> (15 resistor packs for a total of 120 resistors)
>
> I'm trying to figure out if this is overkill ?? (Typically I
> have seen damping resistors used only on the address drivers
> for the SDRAM array)
>
> Thanks,
> Stuart
>
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