At 08:53 PM 3/10/2012, you wrote:
>Good day to all.

<...>

>Anyway, if anyone can suggest a readily-available small dual buffer
>that works at 2.4V and has the normal clamping diodes present on both
>the buffer inputs and outputs, I'd be grateful.
>
>Many thanks!
>
>dwayne

Are you sure that 2.5uA worst case matters? Even with the newer cells
which claim 15% discharge in one year, and 2Ah, that's 34uA internal
discharge current, so you'd be adding less than 10% (discharging to
84% rather than 85% in a year).

As far as the little buffers and gates.. the little guys tend to have
5V tolerant inputs, which obviously means no diodes. You could add them,
of course- a little dual or whatever.

For such a low voltage you may find a P-channel MOSFET is better- for
example the inexpensive SiA427 has 32m ohm Rds(on) with 1.5V drive, which
is below the recommended cutoff for two NiMH cells. It can handle 12A.

BTW, internal resistance of the NiMH cells could cause you some misery
here- it might be approaching half an ohm when the cells are close to
minimum voltage, and you might have trouble getting enough current out of
them without something like a big cap and sequencing the startup somehow
(or using something that doesn't have that nasty characteristic instead).
You definitely don't want the gate voltage to droop too far or it will
fry the MOSFET, but maybe sequence the gate voltage on, into a big cap, and
then turn on the regulators after the gate cap is fully charged.

Best regards,

Spehro Pefhany --"it's the network..."            "The Journey is the rewar=
d"
speff@interlog.com             Info for manufacturers: http://www.trexon.co=
m
Embedded software/hardware/analog  Info for designers:  http://www.speff.co=
m



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