Recurent theme; AVR and femtopower

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Yeah right, I thought 'micropower' and 'picopower' were a bit old and overused :D

Anyway, I would love to see some tutorial and/or experience and/or examples on how to get the maximun battery life out of an AVR -- Atmega if possible.
I'd like to make a project that runs for the longest time on the smallest battery. My benchmark is my lightmeter (Gossen Digisix) that runs for 8+ months on a 3.3V cell, and it doesn't even turn itself off.

I'm a lot more conservative; if I could run (and recharge) every month or so I'd be happy. I'd love to hear about what buck/boost you are using, what IC you use for batery charging, in fact I'd love to hear about the batteries you are using too (NiMH, Li etc)..

I went thru the tutorials, but didn't find anything related.

So far I've been looking for a few months for parts. The buck/boost of Linear Tech seems to be pretty amazing; Texas has some too that looks good, and Maxim has some but they seem 'inferior' at around 80%+ ; compared to the 95%ish efficiency of Linear Tech.
I also know the ins and outs of the AVR datasheet on power saving, I implemented a few of my drivers on interupt/timers and have the main 'thread' just do a while(1)sleep(); sort of things... I'm planning the software allright, but I severely lack on the hardware side :D
I mostly use the m168, but I'm planning to use the 644 and the 1281.. All in 3.3V so far...

So please do brag here, but please quote the part names, and the tips and tricks you found along the way...

Author of simavr - Follow me on twitter : @buserror

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Good idea for a thread, buserror. While the term picopower is fun with the double 'P' sound, perhaps a more apt name for the picopower AVR's would be nanopower: in power-down state with watchdog disabled and low Vcc, the picopowered MCUs use hundreds of nanowatts.

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Quote:

The buck/boost of Linear Tech seems to be pretty amazing; Texas has some too that looks good, and Maxim has some but they seem 'inferior' at around 80%+ ; compared to the 95%ish efficiency of Linear Tech.

Sometimes an LDO works out better than a switcher because the quiescent current when running is usually lower in an LDO. If your load is very light then this makes a difference. For example if you put your micro to sleep then it's current draw is can be in the "sub-uA" range. If your switcher is running at 20uA+ you are "wasting" power since the load is only using <1uA. There are LDOs that have quiescent currents that are in the 5uA range. Anyway this is very application specific since it depends on how the system designed and you have to look at the whole picture.

Another feature to look for is the shutdown ability and its current when in shutdown. Maybe you want to shut some stuff down when you do not need it-- like a periph sensor. Oh which brings up one more comment about switchers, they do draw add'l power/current on start-up so if you duty cycle them you have make sure they'll start-up properly.

PN# LT3014, LT1615, LT1613, TPS77033 where a few I used on some low power stuff.

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Quote:

picopowered MCUs use hundreds of nanowatts

PIC already uses "Nanowatt" so Atmel Marketing 1-upped them with pico power. ;)

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nanovate wrote:
PIC already uses "Nanowatt" so Atmel Marketing 1-upped them with pico power. ;)
Wow, Atmel impressively 1000 times-upped them with buserror providing another 1000-fold power reduction. Take that!, you accurately labeling Microchip ;-)

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Hear that atmel marketing!? Quickly trademark the following:

femtopower
attopower
zeptopower
yoctopower

Some of them sound pretty cool actualy. They'd make a good hype.

There are pointy haired bald people.
Time flies when you have a bad prescaler selected.

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Of course, there's always the 'no power at all' computer, taken to elegant heights with the hexapawn playing and learning matchbox computer described here: http://www.maths.uq.edu.au/~infi...

Um, I seem to have drifted off topic...

Neil :P

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nanovate wrote:
Quote:

The buck/boost of Linear Tech seems to be pretty amazing; Texas has some too that looks good, and Maxim has some but they seem 'inferior' at around 80%+ ; compared to the 95%ish efficiency of Linear Tech.

Sometimes an LDO works out better than a switcher because the quiescent current when running is usually lower in an LDO. If your load is very light then this makes a difference. For example if you put your micro to sleep then it's current draw is can be in the "sub-uA" range. If your switcher is running at 20uA+ you are "wasting" power since the load is only using <1uA. There are LDOs that have quiescent currents that are in the 5uA range. Anyway this is very application specific since it depends on how the system designed and you have to look at the whole picture.

Another feature to look for is the shutdown ability and its current when in shutdown. Maybe you want to shut some stuff down when you do not need it-- like a periph sensor. Oh which brings up one more comment about switchers, they do draw add'l power/current on start-up so if you duty cycle them you have make sure they'll start-up properly.

PN# LT3014, LT1615, LT1613, TPS77033 where a few I used on some low power stuff.

Just to support your recommendations...Darren McInnes and I have just shared in buying 100 pieces of each of the TPS76318 (1.8V output LDO) and the TPS76330 (3.3V output) devices at AUD$0.09 each (about US$0.07). They have a logic driven enable line. When disabled, they draw a maximum of 1 microamp at 25C. They are rated to 150 mA. (Now to find a use for them :lol: ).

Regards,

Ross McKenzie ValuSoft Melbourne Australia

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One technique I've used in a battery application that requires maintainence of real-time is to use a separate RTC chip with its own 3V lithium battery backup. While the picopower AVR's can use a few hundred nanoamps in shutdown mode (and watchdog disabled), to keep real-time they need to awaken periodicallt. Plus you have the quiescent current of the voltage regulator and the other devices connected to Vcc.

Thus, I'll use a separate RTC with a battery backup, and then have the AVR turn off the voltage regulator to power down the circuit. When the AVR is to be used, then a button turns the voltage regulator back on. With Vcc off, the DS1306 RTC use 300nA to keep the oscillator running on battery backup.

Another battery saving choice is choosing an efficient RS-232 level convertor. The plain MAX232 requires 5V and has a significant quiescent current (several milliamps). Maxim makes a number of convertors that have a shutdown mode. My favorite, the MAX3232, uses 3.0-5.5V and has a shutdown mode requiring on 1 microamp (plus has integrated ESD protection saving on the need for additional TVS diodes).

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Quote:

My favorite, the MAX3232, uses 3.0-5.5V and has a shutdown mode requiring on 1 microamp (plus has integrated ESD protection saving on the need for additional TVS diodes).

I second that!

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At work we have data recorder with parasitic power supply from RS-232 lines (mega128L, at45db321, cmos transistor as RS-232 drivers).
Also I use AVR pins as power supply.
For litium Batt processor (AVR) feeds power without stabiliser.
If I need additional power supplay (-5V) I use Cmos logic generator or programm processor pin as generator.
Alexander.

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So what about batteries ? There seems to be tons of small, nice mobile phone batteries; anyone is able to 'recycle' these into projects ?
I won't put serial into projects, I think it's USB or nothing these days -- I already got some of these small USB2 B connectors.

I found some powerhouses, like the Linear LTC3557 thst seems to do pretty juch everything, except coffee; anyone tried these, or similar ?

Author of simavr - Follow me on twitter : @buserror

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buserror wrote:
I won't put serial into projects, I think it's USB or nothing these days -- I already got some of these small USB2 B connectors.

Hey, how come those mini USB connectors have *five* pins, and the normal 'B' and 'A' connectors have four? :idea: :roll:

Neil

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buserror wrote:
Linear LTC3557 thst seems to do pretty juch everything, except coffee; anyone tried these, or similar ?
No I haven't. Seems like a good chip. Just ordered some samples.

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Hey, how come those mini USB connectors have *five* pins, and the normal 'B' and 'A' connectors have four? Idea Rolling Eyes

UID pin, I'm working with it for my MyUSB USB driver for the USB-hardware enabled AVRs. It can select device or master mode when enabled.

- Dean :twisted:

Make Atmel Studio better with my free extensions. Open source and feedback welcome!

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I found these guys, they make lots of various battery packs, but I'm very interested especialy by their rechargeable coin cells..

Anyone played with these ? I think I could run a project reasonably well with 2 of them and a buck converter ?

http://www.powerstream.com/licoi...

they also have a huge range of 'normal' cells of bigger capacity...

Author of simavr - Follow me on twitter : @buserror

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I prefer USB charger max1811.It has more user frendly package SO-8 than LTC QFN-28.
Alexander.

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The newer AVR USB devices have a wake up from sleep using the USB interface. You could also take a look at those (if you haven't already).

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zauberer : nice package, I ordered sample. I still need a regulator behind it, but at least this sorts out the in-place charging...

Kevin: Would your DS1306 'trickle charger' option charge one of these neat rechargeable coin cells I mentioned in the URL a couple messages up ? That would be a perfect solution ! :D

Author of simavr - Follow me on twitter : @buserror

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buserror wrote:
Kevin: Would your DS1306 'trickle charger' option charge one of these neat rechargeable coin cells I mentioned in the URL a couple messages up ? That would be a perfect solution ! :D
Hi Michael, back from our Alaskan vacation. I expect it would likely work, but one would have to carefully read the battery and DS1306 datasheets for this. The DS1306 has flexible powering and the datasheet shows a number of power configurations, including use of rechargable batteries: http://datasheets.maxim-ic.com/e...