From: Mike Harrison
Subject: Re: switching dc-dc: DIY or off-the-shelf
Organization: White Wing Logic
X-Newsreader: Forte Agent 1.9/32.560
Date: Sat, 07 Dec 2002 11:03:21 +0000
NNTP-Posting-Date: Sat, 07 Dec 2002 11:03:53 GMT
On Fri, 6 Dec 2002 22:07:46 -0500, "Mike" wrote:
>Hi, I'm wondering if anyone has any opinions regarding the use of
>off-the-shelf DC-DC converter modules (around $25 for 10 watts) or doing it
>yourself (with e.g. the National Semi 2592HV) (about $10 total). Note that
>this is for 48 volt in, so it's a little more complicated. Are there any
>drawbacks to the DIY approach, and if not, why doesn't everyone do it
>instead of using the modules? In the little testing I've done, it seems
>that the DIY aproach has a lot higher EMI, but I don't know if that's the
>only problem. Any thoughts?
Depends if it's a 1-off, a small production run or large volume.
DIY is more design effort, but has the advantage that it can be
tailored to your application, and usually fitted on the PCB with
EMI is down to good PCB layout. It's unlikely to be hard to get EMI
good enough for approvals - if you have particularly sensitive stuff
near it it may be a little harder, but using an off-the-shelf unit may
be no better in this respect.
With off-the-shelf unit, you also run the risk that the manufacturer
will change the design without telling you. here may also be a higher
risk that they may discontinue it - this is less likely to happen with
a DIY solution.
The bottom line is to balance the extra cost of buying ready-made
units against your time & effort designing a DIY solution.
Switchers using the NS parts are not especially hard to get to work
well, and personally I'd only ever consider a ready-made unit for
1-offs or where an isolated output is needed, which usually needs