ext PSU protection

Hi,

I am currently running a TS7250 from a ext power supply that uses an
adjustable buck regulator to drop to 6.5V then a 78 series linear
reg. to trim to 5V.

The units need to be able to accept a wide range of switch mode DC
supply voltages and I don't want the regulator ruining the amazingly
low power drain of the TS boards by consuming 5 times more than the
board itself.

I'd like to trim the component count and cost by using just a 5V buck
regulator but I'm a bit wary of startup or some glitch blowing the
board.

I considered a crowbar and polyfuse but it looks counter productive
in cost and complexity.

Any suggestions?

Thanks.

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.

On Mon, 12 May 2008, j.chitte wrote:

> Hi,
>
> I am currently running a TS7250 from a ext power supply that uses an
> adjustable buck regulator to drop to 6.5V then a 78 series linear
> reg. to trim to 5V.
>
> The units need to be able to accept a wide range of switch mode DC
> supply voltages and I don't want the regulator ruining the amazingly
> low power drain of the TS boards by consuming 5 times more than the
> board itself.
>
> I'd like to trim the component count and cost by using just a 5V buck
>; regulator but I'm a bit wary of startup or some glitch blowing the
> board.
>
> I considered a crowbar and polyfuse but it looks counter productive
> in cost and complexity.
>
> Any suggestions?

The regulator provided with the metal case that TS sells is a straight
buck reg which seems to be an LM2672 (260khz simple buck switcher), so
that method works fine as long as the frequency is high and the filtering
is sufficient.

If it's really important to you, the TS7260 has onboard buck regulators
and can accept 4.5 to 20v at its power input.

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.

--- In ts-7000%40yahoogroups.com">ts-7000yahoogroups.com, "j.chitte" <j.chitte...> wrote:
&gt;
> Hi,
>
> I am currently running a TS7250 from a ext power supply that uses an
> adjustable buck regulator to drop to 6.5V then a 78 series linear
> reg. to trim to 5V.
>
> The units need to be able to accept a wide range of switch mode DC
> supply voltages and I don't want the regulator ruining the amazingly
> low power drain of the TS boards by consuming 5 times more than the
> board itself.
>
> I'd like to trim the component count and cost by using just a 5V buck
> regulator but I'm a bit wary of startup or some glitch blowing the
> board.
&gt;
> I considered a crowbar and polyfuse but it looks counter productive
> in cost and complexity.
>
> Any suggestions?
>
> Thanks.
>

Some of our systems need to be fed from what is nominally 48VDC but due to charging of
the batteries, can exceed 60VDC sometimes. I found a DC/DC converter from V-Infinity,
part no PTK10-Q48-S12 which has an input range from 20 to 72V, with output of 12VDC
at 0.9A. You could probably find one that output the 5VDC you require. It's a single
encapsulated component, available from Digi-Key and probably other sources.

It's a switched-mode unit, so much more efficient than a linear regulator.

HTH

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.