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'Battery powered device (was low Power Comparators-'
1999\10\19@210739 by Thomas Brandon

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I gather the Analog Devices MAX666 equivalent would be the ADM666(A?). Any
particular reason you decided not to use this? I am looking at a data
aquisition system and was considering adding battery operation. I was
thinking of using the configuration described in the ADM666A datasheets. In
this the voltage regulator is connected to both external power and
rechargable (NiCad in example) battery power. Through it's low voltage
detects, it is used to automatically trigger trickle charging of the
rechargable batteries of the power supply when they are low on charge. Due
to the use of NiCad's it deischarges them through a LED first to prevent
memory.

I probably would have tried to use a rechargable cell without memory to
allow trickle charging during normal mains powered operations. Were there
any particular problems with the ADM666 that you found? Would they effect
this application? Is there an easier\cheaper way to do this? Can anyone
suggest a replacement for the Analog Devices voltage regulator? I live in
Australia and have found Analog Devices parts very hard to source, which is
a pity as they have a lot of nice looking products.

Tom.
{Original Message removed}

1999\10\19@220812 by Dennis Plunkett

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At 11:11 20/10/99 +1000, you wrote:
>I gather the Analog Devices MAX666 equivalent would be the ADM666(A?). Any
>particular reason you decided not to use this? I am looking at a data
>aquisition system and was considering adding battery operation. I was
>thinking of using the configuration described in the ADM666A datasheets. In
>this the voltage regulator is connected to both external power and
>rechargable (NiCad in example) battery power. Through it's low voltage
>detects, it is used to automatically trigger trickle charging of the
>rechargable batteries of the power supply when they are low on charge. Due
>to the use of NiCad's it deischarges them through a LED first to prevent
>memory.

Use the AD device, ask Andy why, as we both have been caught with the
voltage overshoot by the MAX part

Dennis





>
>I probably would have tried to use a rechargable cell without memory to
>allow trickle charging during normal mains powered operations. Were there
>any particular problems with the ADM666 that you found? Would they effect
>this application? Is there an easier\cheaper way to do this? Can anyone
>suggest a replacement for the Analog Devices voltage regulator? I live in
>Australia and have found Analog Devices parts very hard to source, which is
>a pity as they have a lot of nice looking products.
>
>Tom.
>{Original Message removed}

1999\10\20@122146 by William K. Borsum

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At 11:11 AM 10/20/99 +1000, you wrote:
>I gather the Analog Devices MAX666 equivalent would be the ADM666(A?). Any
>particular reason you decided not to use this? I am looking at a data
>aquisition system and was considering adding battery operation. I was
>thinking of using the configuration described in the ADM666A datasheets. In
>this the voltage regulator is connected to both external power and
>rechargable (NiCad in example) battery power. Through it's low voltage
>detects, it is used to automatically trigger trickle charging of the
>rechargable batteries of the power supply when they are low on charge. Due
>to the use of NiCad's it deischarges them through a LED first to prevent
>memory.

We are in fact using the ADM666A--cheaper and better part.  Although on new
designs,
we are moving to the Telcom TC55 series regulators, and separate
comparators for low battery detect.  Gives better LDO voltage and MUCH
lower quiescent currents.

>I probably would have tried to use a rechargable cell without memory to
>allow trickle charging during normal mains powered operations. Were there
>any particular problems with the ADM666 that you found? Would they effect
>this application? Is there an easier\cheaper way to do this? Can anyone
>suggest a replacement for the Analog Devices voltage regulator? I live in
>Australia and have found Analog Devices parts very hard to source, which is
>a pity as they have a lot of nice looking products.

We did have some problems with the 666's as I recall--was some time
ago--and involved not reading the spec closely enough.  The part does
require the series current sense resistor on the output for best stability
and over-current protection--and the comparator had a quirk where it would
suck large amounts of power under certain conditions--may have involved
protection diodes, or some such.  But once we got it figured out,
production units have been working reliably in some pretty nasty environments.

Telcom stuff is available through DigiKey--as are the Maxim parts.  For
analog devices, you unfortunately will need to go to a distributor.

Kelly

William K. Borsum, P.E. -- OEM Dataloggers and Instrumentation Systems
<spam_OUTborsumTakeThisOuTspamdascor.com> & <http://www.dascor.com>San Diego, California, USA

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