Re: Best method for dropping supply voltage a volt or two for low power device?
- From: John Larkin <jjlarkin@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx>
- Date: Tue, 22 Apr 2008 21:22:43 -0700
On Tue, 22 Apr 2008 10:13:30 -0600, "Jon Slaughter"
<Jon_Slaughter@xxxxxxxxxxx> wrote:
What is the best method for dropping the voltage of a device that has a
range of 8 to 12V powered by a car battery(so max, say 14V) to bring it
within spec? The device uses from 100uA to 3mA depending on state.
I was thinking I probably could just use a diode or two and that should be
fine but it would take about 4-6 to do it though and that assumes the
battery is fully charged.
Seems like a regulator is overkill though(as I do not need regulation). I
pretty much want the cheapest solution that will work.
I'm thinking of a simple zener regulator, say at 9V with a ~700 ohm current
limiting resistor but this doesn't seem to work all that well over the whole
supply range.
Basically I'd like something that will drop 2V when the supply is at about
14V and 0V when its at 8V. I imagine this is to much trouble and probably I
won't find a better solution than just two diodes in series? Although this
won't let me run the device if the voltage drops down past 10V ;/).
The biggest problem is that with low current draw(100uA) and high
voltage(14V) it will drop, say, 1V, but at high current draw(3mA) and low
voltage(8V) it will drop 2V ;/ So seems like I can't have my cake an eat it
too ;/
The zener regulator also has a similar problem unless I want to waste a lot
of power ;/
Any other methods I should look into that won't be to expensive? I thought
about DC-DC converters but I'd like to avoid the additional cost and all the
extra components.
(essentially the zener diode will work if I could somehow remove it from the
circuit as the supply voltage decreased. Maybe a transistor could accomplish
this?)
Thanks,
Jon
Hey, I have a brilliant idea: use a voltage regulator!
John
.
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- From: Jon Slaughter
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