Re: voltage regulator accuracy

Isaac wrote:
On Oct 23, 3:35 pm, Tim Wescott <t...@xxxxxxxxxxxxxxxx> wrote:
Isaac wrote:
hi all, i'm teaching myself via books and online material just for the
fun of electronics... i have built from spare parts a simple +5v power
supply using an NTE 5v regulator... however, when i measure the
voltage output, it is at 4.91v... i also have a basic stamp board...
on the basic stamp board the voltage regulator is a precise 5v... is
this due to the manufacturing or possibly my design?... what will the
impact be on my projects if the voltage is slightly less than 5v?..
thanks!
NTE buys floor-sweepings from the semiconductor fabs, then marks them
with their own numbers.

_Any_ voltage regulator will be inaccurate. The more you spend, the
better accuracy you'll get.

Not knowing the voltage regulator that you used its hard to say how much
your design could impact the output voltage. Any 3-terminal voltage
regulator will drop out of regulation if your input voltage is too low.
How much is too low depends on the regulator: a garden variety
regulator will have a drop out voltage as high as 2V, "low drop-out"
regulators are specifically designed to work down to a few hundreds or
tens of millivolts differential.

--

Tim Wescott
Wescott Design Serviceshttp://www.wescottdesign.com

Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" gives you just what it says.
See details athttp://www.wescottdesign.com/actfes/actfes.html

thanks, tim... i can't recall the part number at the moment... do you
have any recommendations for a more accurate regulator?... at the
moment, i'm at the mercy of dozens of cryptic numbers in digikey et
al. catalogs or a local fry's (who seem to sell only nte products)...

I forgot to mention: The necessary accuracy of the voltage regulator depends on what you're driving. Check the data sheets (they're on the manufacturer's web sites) for the required input voltages, then make sure your regulator accuracy matches.

Generally you'll find that it's easy to get regulators that are good for +/-5% over temperature, and that that's good enough for most digital logic.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" gives you just what it says.
See details at http://www.wescottdesign.com/actfes/actfes.html
.

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