[SI-LIST] Re: SMPS capacitor
- From: DAVID CUTHBERT <telegrapher9@xxxxxxxxx>
- To: movax@xxxxxxxxx
- Date: Fri, 7 Mar 2014 06:30:11 -0700
A solar array and the wiring connecting it to the SMPS make a fine antenna
for radiated EMI. So, the SMPS input EMI filter should be designed so that
DM and CM noise conform to the common conducted EMI standards.
Dave Cuthbert, iNARTE certified EMC engineer
Rubium Technology LLC (a consulting company)
On Fri, Mar 7, 2014 at 12:24 AM, Krunal Desai <movax@xxxxxxxxx> wrote:
> On Thu, Feb 20, 2014 at 6:05 AM, Istvan Novak <istvan.novak@xxxxxxxxxxx>
> wrote:
> > Regarding evaluation and demo boards from vendors: we need to understand
> > the purpose and limitations of those boards. The purpose is to
> > demonstrate the correct operation of the circuit. The motivation is to
> > show the ultimate benefits of the vendor parts, sometimes regardless of
> > user constraints. This leads us to the limitations of the evaluation
> > boards: there is no way for the vendor to create demo boards for the
> > very large number of possible permutations resulting from different user
> > applications and layout. The clamshell layout is actually one of the
> > best possible arrangements for the converter itself: it minimizes loop
> > inductance, can help to reduce parasitic ringings, maximize density and
> > efficiency. We can use a clamshell layout when it does not upset
> > anything on our board (nothing sensitive going through the same plane
> > cavities) or when we can place the clamshell converter circuit into an
> > isolated area of the board (isolation means that we cut the planes
> > around the converter so that they dont carry the noise around).
>
> Agreed Istvan; this demo board in question actually has long stubs off
> the gate signals to facilitate probing, obviously not ideal for a real
> application :)
>
> > Regarding the placement of bulk capacitors: in fact there are
> > conflicting requirements. The bulk capacitors handling the DC-DC
> > converter output ripple current would need to be closer to the
> > converter, whereas the bulk capacitors handling the load transients may
> > need to be closer to the load. On a small plane shape this usually does
> > not matter; it becomes a relevant question and dilemma at high current
> > larger planes. Suggested solution: split the bulk capacitors and
> > distribute them according to the occurrence of transients.
>
> I have run into this issue now, with a very constrained layout where I
> think I may be forced to place an output capacitor on the opposite
> side of the board from the converter. The MOSFETs, inductor and gate
> driver are all on the top layer, in addition to a 22uF + 0.1uF ceramic
> output capacitor. If I place a healthy amount of vias (which I will
> anyway to facilitate delivering power into the plane), what is the
> mechanism of the cavity mode injection I may see if I have the 100uF
> bulk output cap on the opposite side? Must I keep a healthy anti-pad
> area on every layer to attempt to avoid noise injection?
>
> The input to this converter is a solar array, which space constraints
> may also force me to place the capacitors on the opposite side of the
> board from the high-speed current loop.
>
> Thanks,
> Krunal
> ------------------------------------------------------------------
> 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:
> //www.freelists.org/webpage/si-list
>
> For help:
> si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
>
>
> List forum is accessible at:
> http://tech.groups.yahoo.com/group/si-list
>
> List archives are viewable at:
> //www.freelists.org/archives/si-list
>
> 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
or to administer your membership from a web page, go to:
//www.freelists.org/webpage/si-list
For help:
si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
List forum is accessible at:
http://tech.groups.yahoo.com/group/si-list
List archives are viewable at:
//www.freelists.org/archives/si-list
Old (prior to June 6, 2001) list archives are viewable at:
http://www.qsl.net/wb6tpu
Other related posts:
