Simplest 3V3/1V5 supply for FPGA...

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davorin

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What are you using for powering a 3V3/1V5 FPGA let´s say from a 12V DC source?

Would like to keep components count as low as possible (so is price ;o) since it is for an evaluation board design...

I know the National simple-switcher products but someone suggested not to use them...

Also rceived TPS70348 samples from TI (combined 3V3/1V5 LDO regulator) but this needs still a 5V regulator upfront...not a bad idea since 5V would be in some cases needed for periphals like PS2 keyboard...
 

Nice...but not usable for unregulated 12V DC (o;

5V to 3V3/1V5 is no problem with low component count like with the TI chip....
 

Use a 7805...

Code: 
                 7805
               +-------+
+12V -----+----|1     3|----+--- 5V regulated
          |    |   2   |    |
    100uF =    +-------+    = 10uF
          |        |        |
 GND -----+--------+--------+--- GND

Those are 3-pins. 1 amp comes in a TO-220 package, cheap, popular.
 

Please no obvious stuff (o;

And not very efficient....
 

Try ON semiconductors NCP1575 aplication 12V-2.5V demoboard.Here is the PDF:
 

Please no obvious stuff (o;

And not very efficient....
Click to expand...

Well, I know it's obvous... but...

Would like to keep components count as low as possible (so is price ;o) since it is for an evaluation board design
Click to expand...

It obvously an easy, low component count design! Well, I didn't saw mentions about efficiency

For more efficiency though, you would probably go with some form of switching regulator...
 

Looks like I´m gonna drop the 12V-5V regulation anyway and just leave it as 5V input-only design...

Otherwise favouring the Nationals simple switcher or ONSemi (ex. Motorola) MC33/34 series switchers....
 

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