AVR-Chat

Hello Mr. Richard Cooke,

Here is a checklist provided by our area Atmel FE Mr. Eric Feign for those
doing low power work. It has some good points. It seems that there are some
other areas of your design to be considered as the processor must do
something and there may be other chips/circuits to do something that may
dictate whether you need regulation or not. Using a CR2032 type small coin
battery requires careful attention to power needs as 250mAH is pretty thin
so the list below will be important.

Give the group more info into what you want to accomplish and there will be
lots of help flow...

Jim

Low Power Checklist

1. Operate at lowest voltage possible since power is proportional to V^2.
2. Depending on application:
  A. Sleep as much as possible then operate at as a high a frequency as
possible in order to get back to sleep sooner.
  B. For applications that may not be able to take advantage of sleep,
operate at as low a frequency as possible since    power is proportional to
F.  Can take advantage of Clock Prescale Register CLKPR.  Can use low
frequency crystal or 128kHz internal RC.
3. Turn off peripherals not in use.  Take advantage of Power Reduction
Register PRR if available.
4. Use Low Power Crystal Oscillator fuse setting for applications requiring
crystal timing accuracy in low noise environments.
5. Enable internal pull-up on unused inputs; use external pull-ups if low
power during reset is important.
6. Disable Analog Comparator when not required (ACD bit in ACSR).
7. Disable Watchdog Timer if not required.
8. Disable Analog to Digital Converter if not required (ADEN bit in ADCSR,
If sleeping in other than Idle or ADC Noise Reduction modes, set ADEN=0
before sleep.
9. Use Digital Input Disable Registers (DIDRx) for those dedicated ADC
analog inputs.
10. Disable Brown Out Detect if not required.
11. Disable On Chip Debug system with DWEN fuse if not required.


----- Original Message ----- 
From: "Richard Cooke" <rcooke@digitalwavelength.com>
To: <AVR-Chat@yahoogroups.com>
Sent: Wednesday, November 29, 2006 4:27 PM
Subject: [AVR-Chat] 3V supply - need regulator?


> Hi Folks,
>
> I'm working on a battery powered consumer product that will use a 3V
> button cell.  I think we've settled on the CR2032 which has a capacity
> of 225uAH.  Our circuit will use an ATtiny13 @ 1MHz along with a few
> other items.  The total current consumption is about 2.65ma when
> always ON.  I think I can reduce that to about 460uA by cycling the power.
>
> My question to the group - can I just use the battery or do you think
> I'll need some type of regulator?
>
> The application will be mostly in the off state.  I'm planning to have
> the unit ON after being plugged into the  item to be controlled and
> then after 10 minutes go into the low power mode and then after 30
> minutes turn itself off.
>
> Thanks,
>
> Richard Cooke
>
> <<< snip >>>