Re: [N8VEM-S100:2046] Voltage Regulator

[David Riley <frave...@gmail.com>]

On Nov 13, 2013, at 1:18 PM, Rob Doyle <radi...@gmail.com> wrote:

> On 11/13/2013 10:07 AM, David Riley wrote:
>> On Nov 13, 2013, at 11:38 AM, monahanz <mon...@vitasoft.org> wrote:
>> 
>>> Excuse the above quick comment. I re-read the post.  Do I
>>> understand it that for currents near 2 amps and above we are better
>>> going with TO-3's.   Using an 8 to 8.5V input.
>> 
>> In general, a TO-3 will handle high current better, but they're also
>> designed to be attached to much bigger heatsinks if necessary (e.g.
>> ones that cover the side of an entire chassis).  You're not going to
>> get significantly better thermal performance out of a TO-3 attached
>> to a small heatsink than you will out of a TO-220 attached to a
>> similarly sized one (though it is obviously better than zero
>> benefit).
> 
> There are a number of manufacturer that make switching power supply
> modules that 'fit' TO-220 pads.
> 
> I've used the TI PT78HT205 previously. Not cheap but worked fine. I
> notice that it seems to obsolete now.
> 
> Digikey and Mouser have 78SR5 modules that are fairly inexpensive
> ($4.30) and are rated 1.5A and 2.0A. At 95% conversion efficiency, heat
> sinking would be a moot point.

I think I had mentioned those previously, but possibly the email got lost.  They're really the best solution for preexisting boards, because they're absolute drop-in replacements for the 7805 (same pinout and everything).  As you say, not cheap, but for some they might be worth it for the reduced hassle.  The 1.5A ones in particular aren't really terribly priced (and the 2A ones are big enough that they might not offer enough clearance on a packed board, though they're probably still smaller than a lot of heatsinks).

You can get much denser "bricks" that provide a lot more power (you could easily get 5A in the area footprint of a TO-220 plus a heatsink, never mind a TO-3 plus heatsink), but they're not drop-in replacements for the same pinout.  Still, for new projects, they're not a bad idea (especially as we begin to talk about real beasts like 486 boards).

For example: http://www.mouser.com/ds/2/167/PVX012A0X-33763.pdf ($11/ea in single quantity)

- Dave