I have tried many time to use resistor arrays for the very reason you
mention but ended up getting back to single resistor, here are a few
reasons why :
Layout :
Resistor and capacitor arrays will reduce real estate only in the case of
bus lines, and then they need to have a small enough pin pitch and kind off
"drop-in" directly on top of the bus layout (which you usually don' t want
to spread apart to match larger pith ... and loose real estate).
Electrical:
Serial resistor should be usable but then pull-ups and pull-downs have a
common pin which can be a problem at high frequency due to the lenght of
the inner line. This is also a problem for capacitor array since the path
to ground might be too long.
When used as terminator, resistor need to be placed at the very end of the
line next to the last IC input pin, when busses are distributed around an
IC, you don' t want to get it back out to the array.
Jean-Luc Lehmann
"Stephen R.
Gregory" To: [log in to unmask]
<SteveZeva@AO cc:
L.COM> Subject: Re: [TN] Capacitor 0603 vs 0402...why not networks and arrays?
Sent by:
TechNet
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09.08.01
02:46
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SteveZeva
Hi Glenn!
I've read the responses you've received to your question (they've all been
good), and want to ask another question...
I assume the reason to use smaller passive components, is to reduce the
real
estate needed by these components. My question is; why isn't there more use
of chip resistor networks and capacitor arrays?
To me, it seems obvious that the use of these components will reduce real
estate, but I don't see them being used as often as they could be...maybe
I'm
not aware of the electrical characteristics or something else, but I wonder
why they aren't used more often in designs that are tight for space than
what
I've seen so far...
Can anybody shed some light on this?
-Steve Gregory-
Hi all,
I'm brainstorming on risks and benefits of 0603 caps vs 0402 caps.
If the cap value, voltage rating, dielectric material, terminations, and
use conditions are the same, would one be better than the other? My
thoughts are it would be a wash or at least not significant. Here's what
I
have so far:
Benefits of 0402 vs 0603:
Smaller size reduces thermal stress/strain on solder joints from CTE or
board flexing.
Smaller size uses less real estate on board
Risks of 0402 vs 0603:
Equipment may have difficulty placing
Thinner dielectric spacing to achieve same capacitance, cap higher failure
rate
Smaller size, cracks easier to develop
Higher risk of tombstoning
What do you all think? I'm sure I missed something, maybe even
wrong on some of the above.
Thanks,
Glenn
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