Ok, the only "low dropout regulator" maplin has is..

http://www.maplin.co.uk/products/Module.asp?CartID=0207191520161455610&modul
eno=8063&modulecode=

To quote the link:

      Specifications:
      Output voltage: 5V typical 10.15V max.
      Line regulation: 20mV
      Load regulation: 35mV
      Output impedance: 35mW
      Quiescent current: 10mA max.
      Output noise: 1505V rms
      Ripple rejection: 72dB min.
      Long term stability: 20mV/1000 hrs
      Dropout voltage: 0.5V min.


Does the "droupout voltage 0.5V min." mean I have to supply 5.5V as a
minimum?  Will this work with my 4 AA batteries ? :)

Thanks,
Kieren

----- Original Message -----
From: "Olin Lathrop" <olin_piclist@EMBEDINC.COM>
To: <PICLIST@MITVMA.MIT.EDU>
Sent: Friday, July 19, 2002 1:43 PM
Subject: Re: [PIC]: Flashing LED Episode II (small attachment)


> > I fixed the MCLR-wrong-polarity thingy, added a resistor, and a zener
> diode
> > to regulate instead.  But, a question (which my books don't appear to
> answer
> > properly!) - would I use a 5.1V zener to drop the voltage to 5.1V, or a
2V
> > zener to drop the voltage (from 6V) to 4V?; I would assume that the
latter
> > is true, because a website told me they have a "specified voltage
drop" -
> > but to quote Mr. Dude, "a 5.1V zener".
> > Just to clear that up..
>
> A zener in this context is used as a shunt regulator.  In other words, you
> put it accross the PIC and the zener draws enough current to drop the
> incoming voltage down to 5.1V or whatever.  This also requires a resistor
in
> series with the battery for the zener to react against.  Short answer:
This
> is a really bad idea in this case.  Keep in mind that many people on this
> list will offer advice, but the quality of that advice should be suspect
> until nobody objects to it for 24 hours or so.
>
> You had the right idea originally by using a voltage regulator.  The
LM7805
> is not a good fit because it requires too much headroom, but an LDO (Low
> Drop Out regulator) will work fine.  You can also use the hack I mentioned
> earlier about putting a single diode (such as 1N4001, for example) in
series
> with the battery.
>
>
> *****************************************************************
> Embed Inc, embedded system specialists in Littleton Massachusetts
> (978) 742-9014, http://www.embedinc.com
>
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