[SI-LIST] Re: Placement of decoupling capacitors
- From: "S. Weir" <weirsp@xxxxxxxxxx>
- To: khalida@xxxxxxxxxxx, Larry Miller <lmiller@xxxxxxxxxxxxxxxxxxxx>,si-list@xxxxxxxxxxxxx
- Date: Tue, 31 Jul 2001 16:17:03 -0700
Khalid,
If you connect the capacitors to the planes using vias in a low inductance
configuration, you do not need to worry very much about the
placement. Don't try to connect the capacitors to the parts directly via etch.
Regards,
Steve.
At 02:10 PM 7/31/01 -0700, Khalid Ansari wrote:
>Larry,
>
>
> >I think you have it right on placing the smallest caps (highest frequency)
> >closest to the pins, but these are very small (we use 0603's), so the next
>
>I just have enough space to place this one close to the pin, the rest have
>to go quite further away due to space constraint. Placing them too far
>away I have to worry about the loop inductance.
>
>Are there any issues with piggy backing capacitors?
>
> >bigger (lower frequency) ones are not that much further away. By the time
> >you get to the bulk caps, they only have to be in the general neighborhood.
> >
> >No tricks or piggybacks needed-- the lower the frequency range you need to
> >cover the less critical the placement. This is especially true where you
> >have power and ground planes that are essentially zero ohms at lower
> >frequencies.
> >
> >My opinion, anyway, and we haven't had any problems following this idea.
> >
> >Larry Miller
> >
> >-----Original Message-----
> >From: Khalid Ansari [mailto:khalida@xxxxxxxxxxx]
> >Sent: Monday, July 30, 2001 2:19 PM
> >To: si-list@xxxxxxxxxxxxx
> >Subject: [SI-LIST] Placement of decoupling capacitors
> >
> >
> >
> >I looked through various emails from Larry Miller, Larry Smith and the rest
> >who had contributed to a discussion earlier on decoupling. Those
> >emails helped me select the values for decoupling caps but now the
> >challenge is, how do I place these? I don't have enough room on each of my
> >power supply pins to place these caps around. If I try to place the
> >cap that decouples the highest frequency components out of the selected
> >ones close to the power pin and the one that decouples the lowest frequency
> >components the farthest, the caps are being placed too far away from the
> >pin.
> >Can I piggy back these caps? What are some of the tricks to overcome this
> >problem?
> >
> >Thanks in advance,
> >
> >Khalid
> >
> >
> >
> >
> >
> >
> >
> >------------------------------------------------------------------
> >To unsubscribe from si-list:
> >si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field
> >For help:
> >si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
> >
> >List archives are viewable at:
> > //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
> >
>
>
>
>
>
>
>
>
>------------------------------------------------------------------
>To unsubscribe from si-list:
>si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field
>For help:
>si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
>
>List archives are viewable at:
> //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
>
------------------------------------------------------------------
To unsubscribe from si-list:
si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field
For help:
si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
List archives are viewable at:
//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
Other related posts:
