FreeLists / si-list / [SI-LIST] Re: How to select the pullup/pulldwon resistor

["Bill Reams" <breams@xxxxxxxxxxxxxx>]

{snip}


PS> Just recently I was working with a vendor who specified a pullup for =
the
open drain on their chips to be 3.01 K +- 1%. Of course when asked tehy
could not explain such a pickiness in values and eventually agreed to =
allow
4.7K 5% resistors :-)))))

{snip}

I've been on both sides of this "issue". In a past job I designed =
in-circuit simulators and emulators for a couple of microcontrollers. If =
I used a 3.32k pull-up on a line (the circuit would have worked fine =
with a value of 1-50k), guess what went into the reference designs and =
data sheets? So I'm certain that there are designs out there using 1% =
resistors without regard to why.

On the other side, with a pull-up similar to the above 1-50k value =
needed, I've seen reference designs published with pull-ups of 5k. One =
engineer I've worked with was much into copying reference designs =
without regard for what he was doing so. You can guess at the grief he =
got when trying to find 5.0K resistors for his circuit.

The moral of the story is to understand your parts and circuits instead =
of blindly copying someone else's work. Obviously Mr. Nudelman =
understands instead of just copying.
------------------------------------------------------------------
To unsubscribe from si-list:
si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field

or to administer your membership from a web page, go to:
http://www.freelists.org/webpage/si-list

For help:
si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field

List archives are viewable at:     
                http://www.freelists.org/archives/si-list
or at our remote archives:
                http://groups.yahoo.com/group/si-list/messages 
Old (prior to June 6, 2001) list archives are viewable at:
                http://www.qsl.net/wb6tpu