"sycochkn" wrote in message
m...

"Christopher Ott" chrisott at ottelectronics dot com wrote in message
...
I've been using the National "Simple Switchers" with good results for
awhile, and would like to take a step beyond the usual methods of setting
the output voltage. I typically use the fixed voltage versions of the
LM2676 with a resistor in series with R2 to increase the output voltage
when the predetermined +5 or +12 needs adjusted. But now I'd like to
control the output voltage using a microcontroller. I'm pretty sure I
could get this done by using the adjustable version which does not have
R1 or R2, and placing a digital potentiometer in place of R1 with an
appropriate value of fixed resistor for R2. However, I have a spare
channel from an offboard 5 volt D/A which would be cheaper and easier
from a BOM standpoint. I was hoping to get it done with some spare R to R
opamps which are also available.

My analog skills have gotten a little lazy over the years and I'm having
a tough time thinking this one out. I guess the bottom line is that I
need to control the feedback current from the switcher output using a
0-5v DAC output.

Any ideas? I would tend to think this has already been done somewhere by
someone...

Chris


How about an LM2636.

Bob

Looks like the LM2636 only does 3.5 volts (I'm wanting a window of approx
12v to 36v). It's also just a controller. The simple switchers are nice in
that they have integrated FET's in addition to a controller. Much easier on
the BOM and board design end.

Chris