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Clean/small footprint method of stepping 3.3V supply up to 5V, I<50ma?

M

M. Noone

Jan 1, 1970
0
Hi - I just discovered on a set of boards that I'm working on that the
microcontroller that I'm using (Atmel atmega168) requires a 5V supply
for full speed operation. I had planned on giving it 3.3V so now I have
to figure out how to step up the 3.3v supply to 5V. 3.3V line is very
low noise, as it was originally designed to be driving this
microcontroller. Right now - the best solution I've been able to come
up with is the Microchip MCP1252/MCP1253:
http://ww1.microchip.com/downloads/en/devicedoc/21752a.pdf

It steps up 3.3v to 5V up to 150ma, which is more than enough for my
needs. It is an 8-MSOP package and needs three ceramic capacitors. It
is specced for 2.5% accuracy and 45mv ripple. It's not perfect, but I
think it'll probablay work.

My question is this: Are there any better solutions out there? Cost is
not a worry, as this is a very low volume application. Size is my
biggest worry as I was already running out of space on this board
before I discovered that I need a 5V supply.

Thanks,

-Mike
 
M

Mike Noone

Jan 1, 1970
0
Hi - I just discovered on a set of boards that I'm working on that the
microcontroller that I'm using (Atmel atmega168) requires a 5V supply
for full speed operation. I had planned on giving it 3.3V so now I have
to figure out how to step up the 3.3v supply to 5V. 3.3V line is very
low noise, as it was originally designed to be driving this
microcontroller. Right now - the best solution I've been able to come
up with is the Microchip MCP1252/MCP1253:
http://ww1.microchip.com/downloads/en/devicedoc/21752a.pdf

It steps up 3.3v to 5V up to 150ma, which is more than enough for my
needs. It is an 8-MSOP package and needs three ceramic capacitors. It
is specced for 2.5% accuracy and 45mv ripple. It's not perfect, but I
think it'll probablay work.

My question is this: Are there any better solutions out there? Cost is
not a worry, as this is a very low volume application. Size is my
biggest worry as I was already running out of space on this board
before I discovered that I need a 5V supply.

Thanks,

-Mike

Please ignore the above quoted post (as it was accidentally posted twice).
Google Groups sucks. I'll be sticking with ol usenet from now on.

-Mike
 
F

Frithiof Andreas Jensen

Jan 1, 1970
0
How do you get the 3.3V?

Because:

If you already have an on-board step-down switching supply you might be able
to add a fly-back winding on the filter inductor. The auxilliary 5V voltage
will track the 3.3V but not so well; it depends on the ratio of power
between the 3.3V and the 5V.

Obviously, the 3.3V should be the dominant one.
 
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