stepdown dc/dc power

[peter]

Hello all
Just have a techniacl question. Over the passed 2 days I'm trying to
think of a way to build a power suppyly for may magellan sportrak
map(gps) which needs 3.8vdc-4.2vdc that will be converted from cars
12vdc. What is the best way to put that power supply togther ueseing
easy to fing components.

 

[martin griffith]

Hello all
Just have a techniacl question. Over the passed 2 days I'm trying to
think of a way to build a power suppyly for may magellan sportrak
map(gps) which needs 3.8vdc-4.2vdc that will be converted from cars
12vdc. What is the best way to put that power supply togther ueseing
easy to fing components.

Go to www.linear.com and download LTspice/switchercad, this is a
design program for switch mode power supplies, and you can just plug
in the values and a ready made design will appear (by magic)

The main problem will be protecting any design from the nasty 400V
transients on the 12V car supply, google for Load Dump. This is a
significant problem

A simpler way would be to use a LM317 linear regulator, but will be
quite inefficient, and the lm317 will disipate quite a lot of heat
The Load Dump problem is still there
www.national.com for the lm317 datasheet




martin

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