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# wide range voltage input

L

#### ltj

Jan 1, 1970
0
If you had a small 3.3V, 50mA circuit how could you make it to accept a
5-24VDC input range? Cost is an issue.

J

#### John Popelish

Jan 1, 1970
0
ltj said:
If you had a small 3.3V, 50mA circuit how could you make it to accept a
5-24VDC input range? Cost is an issue.

Are you talking about responding to logic signals or measuring analog
signals?

L

#### ltj

Jan 1, 1970
0
oops...for powering the circuit. A regulator will get too hot if I drop too
much voltage across it, so what is a good way to have a wide power input
range?

J

#### John Popelish

Jan 1, 1970
0
oops...for powering the circuit. A regulator will get too hot if I drop too
much voltage across it, so what is a good way to have a wide power input
range?

A switching regulator converts one voltage to another with minimal
power loss. Here is a tutorial on the subject to get you started.
http://www.national.com/appinfo/power/files/f5.pdf

This page on the National Semiconductor site will design a switching
regulator for you, to your specifications:
http://www.national.com/appinfo/power/

That said, 50 ma drawn from a 24 volt source represents only 1.2
watts, total. So a linear regulator would have to waste no more than
(24-3.3)*.05=1.03 watts. That is about what a square inch of heat
sink could dump.

L

#### ltj

Jan 1, 1970
0
John Popelish said:
A switching regulator converts one voltage to another with minimal
power loss. Here is a tutorial on the subject to get you started.
http://www.national.com/appinfo/power/files/f5.pdf

This page on the National Semiconductor site will design a switching
regulator for you, to your specifications:
http://www.national.com/appinfo/power/

That said, 50 ma drawn from a 24 volt source represents only 1.2
watts, total. So a linear regulator would have to waste no more than
(24-3.3)*.05=1.03 watts. That is about what a square inch of heat
sink could dump.

A switching regulator is what I'm looking for.

This is a MUST READ for rookies!
http://www.national.com/appinfo/power/files/f5.pdf.

Don't know what I'd do without S.E.(...),
Thank you very much

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Spehro Pefhany
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