Yeah i think you are right.

I just reread the data sheet and I realized that with the quiescent current
that they specify there should be about a 900 ohm resistance between the
output 5V and the ground.

I had just assumed that there was some sort of diode on those outputs so my
multimeter would not have been able to check the resistance of a voltage
regulator.

thanks,
Adam

On 3/14/07, peter green <plugwash@p10link.net> wrote:
>
>
> > While I was checking a printed circuit board that I made, I found a
> > 900 ohm short between my ground and 5 volts after my low drop out
> > regulater.  I thought that there was something wrong with my circuit
> > until I checked everywhere I could think of.  Finally I measured the
> > resistance on another working circuit (different design) which I made
> > with that same regulator and there was that same 900 ohm resistance.
> >
> > The LDO is the fix 5V of the LD1117 series, digikey number
> 497-1243-1-ND.
> >
> > Could their have been a flaw in the manufacturing run of my parts or
> > is this a fundamental part of low drop out regulators?
> measuring resistances in a constructed cuircuit often wont lead to
> sensible results, with your metering you will be either applying a voltage
> to the output with nothing on the input or worse applying a reverse voltage
> to the output, neither of theese are even close to the normal operating mode
> of the device.
>
> if the regulator is behaving itself (within the parameters in the
> datasheet) with regards to its specs in terms of input current with no load
> i really wouldn't worry about it.
>
>
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