5V to 5V regulators

panfilero · 2013-01-14T16:22:28+00:00

I have 5V from a regulator that's not very well regulated that I would like to feed into a LDO regulator to clean it up a bit.... but I'm not sure how I can do this since I would have to be consistently above 5V in order for the LDO to do its thing.... does anyone know a good way to do this? much thanks

J

John Larkin 13 years ago

going to end up just boosting up the voltage and then regulating after that

use a

I avoid lawyers, even my own.

Where I come from, lots of things get reinvented, not copied, when the technology is right.

John Larkin Highland Technology Inc www.highlandtechnology.com jlarkin at highlandtechnology dot com Precision electronic instrumentation Picosecond-resolution Digital Delay and Pulse generators Custom timing and laser controllers Photonics and fiberoptic TTL data links VME analog, thermocouple, LVDT, synchro, tachometer Multichannel arbitrary waveform generators

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L

langwadt 13 years ago

th, I'm going to end up just boosting up the voltage and then regulating af ter that

ould use a

es.

Today it is easy to crawl the internet an find a solution, before google etc. I'm sure a lot more people were working on the same problem independently came up with the same solution

-Lasse

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J

John Fields 13 years ago

going to end up just boosting up the voltage and then regulating after that

fine.

a

Duh. ;)

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J

josephkk 13 years ago

with, I'm going to end up just boosting up the voltage and then regulating after that

you could use a

diodes.

node

That works pretty well for fairly simple problems. When it starts to get complicated the Internet dries up pretty fast. For serious tradeoffs or challenging questions it can only help to find some useful references, far more are still available at brick and mortar libraries including lots of textbooks.

The publishing industry has a conundrum, in a damned if they do and damned if they don't kind of way. That is per read/view metering or not. Another solution is needed.

?-)

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J

John Fields 13 years ago

going to end up just boosting up the voltage and then regulating after that

fine.

Why strangle the oscillator with one megohm of feedback? ISTM that, for economic reasons, the goal would be to get the frequency as high as possible in order to minimize the capacitance of the pass and reservoir capacitors in the filter and, thus, save some bucks.

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J

John Larkin 13 years ago

going to end up just boosting up the voltage and then regulating after that

fine.

Set the frequency to anything you like; my "ballpark" gives you permission. But it really doesn't need a cap.

Then change the 1M to a short and save more bucks. The thing will scream at some number of MHz and there will be a lot of EMI and heating from shoot-through currents (and diode recovery if you don't use schottkies.) With an HC14, it will be dramatic.

There's no money to be saved by making the caps less than a couple hundred nF.

A three stage ring oscillator would still be pretty fast.

use a

I'd hate for someone to lay out a board using a wimpy PIC PWM or something, and have it not work.

John Larkin Highland Technology, Inc jlarkin at highlandtechnology dot com http://www.highlandtechnology.com Precision electronic instrumentation Picosecond-resolution Digital Delay and Pulse generators Custom laser drivers and controllers Photonics and fiberoptic TTL data links VME thermocouple, LVDT, synchro acquisition and simulation

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J

John Fields 13 years ago

I'm going to end up just boosting up the voltage and then regulating after that

fine.

use a

Yes, that's obvious.

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J

John Larkin 13 years ago

use a

I'd also hate for them to run it at the highest possible frequency.

John Larkin Highland Technology Inc www.highlandtechnology.com jlarkin at highlandtechnology dot com Precision electronic instrumentation Picosecond-resolution Digital Delay and Pulse generators Custom timing and laser controllers Photonics and fiberoptic TTL data links VME analog, thermocouple, LVDT, synchro, tachometer Multichannel arbitrary waveform generators

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J

John Fields 13 years ago

use a

Obvious again.

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J

John Larkin 13 years ago

could use a

So, why did you recommend it?

John Larkin Highland Technology, Inc jlarkin at highlandtechnology dot com http://www.highlandtechnology.com Precision electronic instrumentation Picosecond-resolution Digital Delay and Pulse generators Custom laser drivers and controllers Photonics and fiberoptic TTL data links VME thermocouple, LVDT, synchro acquisition and simulation

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J

John Fields 13 years ago

could use a

diodes.

Well, if not picking nits, one might have come to the conclusion that my choice of a "highest possible frequency" would have been that which resolved the conflict between dissipation in the logic and that of the reactances of the pass and the reservoir capacitor. YMMV.

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Jim Thompson 13 years ago

could use a

diodes.

Birdbrain test nothing, knows nothing. Relying on the pad capacitance to set his oscillator frequency is just plain asinine.

And there are lots of other details that go into designing a good "pump"... my clients know what I do... and I won't tell. My pumps go into cell phone displays where efficiency is critically important. ...Jim Thompson

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5V to 5V regulators

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