[SI-LIST] Re: 1k ohm, 1 inch from uni-directional receiver
- From: steve weir <weirsi@xxxxxxxxxx>
- To: "Loyer, Jeff" <jeff.loyer@xxxxxxxxx>
- Date: Fri, 22 Jan 2010 14:24:31 -0800
Jeff, sometimes things get so old that they become new again. I believe
you will find that particular solution discussed in Howard Johnson's
original HSDD aka "Black Magic" book that is approaching its 20th birthday.
Best Regards,
Steve.
Loyer, Jeff wrote:
> We recently came across an elegant solution for some of our uni-directional
> signals (resets, power_goods, enables, etc.) that tend to go all over, get
> long, have lots of stubs, etc., on big server baseboards. We place a 1k ohm
> resistor 1" from the receiver. The resistor, 1" T-line, and capacitance of
> the receiver act as a nice filter that turns some VERY UGLY signals into
> nice, monotonic rising edges. Of course, the tradeoff is increased risetime,
> which is normally pretty lax for these types of signals. Some lab
> measurements and poking around w/ ADS seems to indicate that 1", 1k is the
> best combination for most situations. But, I haven't done an extensive study.
> Trying to save myself some time & effort, I was wondering if anyone had seen
> something similar to this that has been extensively studied.
>
> Thanks in advance,
>
> Jeff Loyer
>
>
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