[sdiy] Power Supply Design

Stewart Pye stewpye at optusnet.com.au
Fri Jun 10 23:28:46 CEST 2011


I'm designing a 3A power supply PCB for my synth and just want to check 
a few layout rules...

I'm using LD1085 regulators (same pinout as LM317).

It is convenient for me to take the ground side of the adjust pin to 
ground at the output connector, or to the last main filter cap about 
.75" away. Would it be best to take it back to the filter cap?  It is a 
ground plane section between the cap and output connector so there is 
little resistance.

I am taking the ground side of the post reg capacitor directly back to 
the main filter caps with its own track.

On a similar note, I have the resistor between the output and adjust pin 
pretty close to the output pin. Is this normal practice, or is is best 
to run a track to the output connector so that you are measuring the 
voltage at the connector? I'm thinking if you did it that way there may 
be instability problems...

I'm using thick tracks or planes so there should be little voltage drop 
between the regulator output and the connector.



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