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From: Adrian Jansen on 17 Jan 2007 16:22
kikuzo wrote:
> Hello to all..!!!
>
> I'm looking for a single output , 5V @ 1A, DC-DC step down converter
> for an analog application. Does anyone know where can I find one
> module like this ?
>
> Thanks,
>
> Hideo.
>
Recom R7805-1.0

www.recom-international.com

--
Regards,

Adrian Jansen adrianjansen at internode dot on dot net
Design Engineer J & K Micro Systems
Microcomputer solutions for industrial control
Note reply address is invalid, convert address above to machine form.
From: Tam/WB2TT on 17 Jan 2007 17:43

"Joerg" <notthisjoergsch(a)removethispacbell.net> wrote in message
news:pswrh.33724$QU1.30812(a)newssvr22.news.prodigy.net...
> kikuzo wrote:
>
>> Hello to all..!!!
>>
>> I'm looking for a single output , 5V @ 1A, DC-DC step down converter
>> for an analog application. Does anyone know where can I find one
>> module like this ?
>>
>> Thanks,
>>
>
> Check Digikey. For really noise-critical apps I can only tell you from
> experience that I always rolled my own. And beware of "vaporware" PWM
> controllers that look almost too good to be true on the datasheet and then
> turn out to be non-stock everywhere.
>
> --
> Regards, Joerg
>
> http://www.analogconsultants.com

Also, check out Mouser. They have several. Price range will be about $7 to
$25 ea. I am guesssing your input is around 12V.

Tam


From: mpm on 17 Jan 2007 17:54

kikuzo wrote:
> I'm looking for a single output , 5V @ 1A, DC-DC step down converter
> for an analog application. Does anyone know where can I find one
> module like this ?

Without knowing your application, you might look at the National
Semiconductor LM2575T.
It's a switching regulator, but very efficient. We use them in our
audio products here and we don't have problems with noise. (Though
admittedly, our products are not specifically intended to satisfy the
discriminating audiophile...)

Also, (from memory), I think these are good for 1.5A. (?)
I recall National has another line (very similar numbering) that's
qualified to 3A.

The '2575 requires a few extra parts (inductor, shottky diode, in & out
caps), as compared to your standard 7805.
It also has a shutdown pin, if that's useful in your application.
Digikey has them. DIP, TO-220 and surface mt.
They keep changing the part number, but my bin says : "LM2575T-5.0-ND"
for the 5-pin TO-220 variety.

-mpm

From: kikuzo on 18 Jan 2007 02:14
I was not very specific... sorry !!

The application is for measuring several accelerometer and
magnetometers using low noise instrumentaion amplifiers. The input
voltage range is from 9Vdc to 24Vdc. The circuit input current is
about 0.5A and the most important, the output ripple should be
something about 20UVrms (micro volts).

I'm trying to find a DC-DC switching converter instead of a linear
regulator for efficiency and lower power disipation. I used a LT1763,
with excellent low noise output, but it was disipating too much heat.

Thank you all for your comments.

Hideo.

From: miso on 18 Jan 2007 04:27

kikuzo wrote:
> I was not very specific... sorry !!
>
> The application is for measuring several accelerometer and
> magnetometers using low noise instrumentaion amplifiers. The input
> voltage range is from 9Vdc to 24Vdc. The circuit input current is
> about 0.5A and the most important, the output ripple should be
> something about 20UVrms (micro volts).
>
> I'm trying to find a DC-DC switching converter instead of a linear
> regulator for efficiency and lower power disipation. I used a LT1763,
> with excellent low noise output, but it was disipating too much heat.
>
> Thank you all for your comments.
>
> Hideo.

You can always do a DC-Dc and follow it with a LDO. [Drop most of the
voltage with the DC-DC, then do the last volt with the LDO. ] You
probably want the DC-DC in a separate box since the switcher noise
radiates. Put the LDO near the analog circuits. Critical designs have
LDOs per section to increase the isolation, though beware if there is
an issue with the LDOs being slightly different in output voltage.

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