Author Topic: Two voltage regulators  (Read 3271 times)

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Offline Spekkio

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Two voltage regulators
« on: April 30, 2011, 03:07:54 pm »
Can there be a problem having two voltage regulators in one circuit?

I have a 7805 and a LD33CV. This is not permanent though, in the future I'm going to use only 3.3v
 

Offline david77

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Re: Two voltage regulators
« Reply #1 on: April 30, 2011, 03:10:52 pm »
I think to answer your question we'd need more details. Can you post a circuit diagram?
 

Offline Simon

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Re: Two voltage regulators
« Reply #2 on: April 30, 2011, 03:16:22 pm »
yes, what are you doing with them, are you trying to connect them in parallel ?

I'm guessing you have a 5V and a 3.3V driven off it ? that is fine but do remember that the 5V one must be able to take the current for both 5V and 3.3V. If you have a low current requirement of the 3.3V and are dropping to 5V from a high voltage like 12v I'd suggest separating them to take some thermal load off the 5V one unless of course it is well over speced and maybe your trying to get very stable 3.3V
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Offline Simon

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Re: Two voltage regulators
« Reply #3 on: April 30, 2011, 09:05:24 pm »
then fire away, no problems there, just make sure they both have their own decoupling capacitors
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Online Zero999

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Re: Two voltage regulators
« Reply #4 on: April 30, 2011, 09:05:35 pm »
Care to mention how much current is required?

For optimal battery life use a low drop-out regulator for 5V. The 3.3V regulator can be a standard LM317 because the drop-out isn't important.
 

Offline Spekkio

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Re: Two voltage regulators
« Reply #5 on: April 30, 2011, 09:06:30 pm »
they are connected in parallell to a 9v battery.

yes, because after I connected the 3.3V regulator, it seems like the 5v regulator is getting warmer than usual.
or maybe just my imagination, maybe I never touched them before I connected the 3.3V reg, dont remember :D
 

Offline Simon

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Re: Two voltage regulators
« Reply #6 on: April 30, 2011, 09:08:25 pm »
it will have no affect unless the 3.3V part of your circuit affects consumption on the 5V part
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