[sdiy] Seperate Grounds

[Don Tillman]

Local regulators for each module is an approach that is known to work
well, but it seems like a lot of circuitry to spend on regulators.
Also, regulators need a minimum load current and if the module is one
that uses just a tiny bit of current some additional current will have
to be wasted to keep the regulator running.

The approach I'm using for my current project is to run all modules
off a common +/- 15 volt regulated supply with the following
'contract' for the modules:

  Each module assumes that the power supply is not precise.  If a
  module needs an accurate voltage source then that module is
  responsible for creating that voltage locally.

  Modules are not allowed sudden changes in current draw.  So any LEDs
  are driven by current steering.  And sawtooth resets are generated
  by shorting caps instead of slapping them up to the supply voltage.

  -- Don

-- 
Don Tillman
Palo Alto, California, USA
don at till.com
http://www.till.com