Battery powered applications

[NavMicroSystems]

I would like this thread to collect Info about the Hardware Design of Battery Powered Applications.

(All the Do's and Dont's)

So far I never really had to care about "power consumption"
as my applications have always connected to Power Supplies with almost "infinite" capacity.

Now I have got the challenge to design a battery powered "standalone" device
that has got to be "as small as possible"
and should run reliably for at least 6 months without the need to recharge/replace the battery.

I have got to run the the Board at exactly and stable 5.00 V as there are some analog sensors.

All Linear LDO's I have found so far do have a quiscent current that would flatten
a "small" Battery within that period of time.

How do you solve this kind of problem?

Again:
I'm not asking how to reduce the Systems power consumption by turning off peripherals,
the question is about the design of the power supply.

[Melanie]

Here's a thought straight off the top of my head...

The chances are your sensors will produce an output proportional to Vdd applied. The ADC's will give you a result proportional to Vdd. You therefore probably don't have to worry about a too stable Vdd as the two (ADC and sensor) will still be in proportion respective to Vdd. Anyway, since when did regulators ever give you 5.000v? So run your product at 3v or 4.5v and lose the hassle, expense and power consumption of the whole Regulator circuitry.

[NavMicroSystems]

Thanks Melanie,

you are right, chances are that the regulators are slightly off 5.00V, this is something I could compensate as long as the output is relatively stable and there is not too much drift.

Some of the sensors are integrated types and require a 5.0V supply, so running the circuit at 3.3V or 4.5V is not an option.
For higher resolution I'm using an external ADC.

The LP2950 Regulator has an initial tolerance of 0.5%
and a line regulation of 0.05%
quiescent current is 75µA "only"

I'll give it a try.

Or do you know any "better" Regulator?

Worst case I would have to solve the problem by throwing battery capacity at it

[NavMicroSystems]

GOOD NEWS:

I have got the standby current down to less than 200µA !

[georgex5]

Can you add on a few solar cells?

[Ron Marcus]

Seiko makes LDOs with 10 uA standby current. They are in Mouser.