[sdiy] Isolating a +-15v/+5v PSU?

[Seb Francis]

Jeff Farr wrote:
>
> And now, a question about Star grounding VS using a ground plane:

I would try and do both if possible.  Have the PSU (or PSUs) in the 
middle of the board and have a separate analog and digital ground plane 
on each side of the board, joined only at the PSU.

Take a look at this as an example:
http://burnit.co.uk/sdiy/index.php?page=4xd&subpage=layout
Scroll to the bottom copper view and you can see the analog ground plane 
is on the right, and the digital ground plane takes most of the left 
(except for the CV input area on the bottom left which is connected to 
the analog ground plane).  It's not shown on the layout, but these 
ground planes are joined at the rectifier diodes (and only here).

In this design I am using 2 regulators - 1 for +5V digital and 1 for +5V 
analog - they sit either side of where the 2 ground planes join (you can 
see this on the component layout image at the top of the page).

If you are regulating +5V digital from the analog +15V I would put a 
ferrite bead in between with a smoothing cap after the bead and before 
the +5V regulator.

Seb