I'm trying to get Moteino (R2) running from 3V coin cell with maximum battery life. At 16Mhz it's a little out of spec, so I uploaded 8Mhz bootloader.
Then came a surprise. When running Moteino at 3.3V power usage during AVR watchdog sleep is pretty good (9 microAmps). But as soon as I drop voltage to 3.0V power usage goes up to 86uA during sleep. Using same exact sketch which sleeps for 8 seconds (watchdog timer) and then wakes up and sends transmission over RFM12b (blinks LED too).
Just to get a baseline I setup ATMega328p on breadboard with RFM12b (via breakout I made). It was using 8uA at any voltage (from 2.8V to 3.3V) during sleep.
Here' are more details:
Moteino R2 (RFM12b) at 8Mhz clock:
⁃ At 3.3V connected to VIN: Max: 5.3mA Min: 0.009mA
⁃ At 3.3V connected to 3.3V: Max: 5.5mA Min: 0.009mA
⁃ At 3.0V connected to VIN: Max: 4.7mA Min: 0.086mA
⁃ At 3.0V connected to 3.3V: Max: 4.2mA Min: 0.086mA
Bare bones ATMega328p @ 8Mhz w/ RFM12b
⁃ At 2.8-3.0V : Max: 5mA Min: 0.008mA
⁃ At 3.3V : Max: 4.5mA Min: 0.008mA
⁃ At 2.7V not working
I suspected it might have something to do with MCP1703 Voltage regulator, but I'm bypassing it when plugging into 3.3V pin, right?
Anyone seen similar issue?
I'm attaching my sketch just in case (although it's configured to sleep for 5 minutes by default).
If you're running through the 3.3V regulator that is the problem. This was discussed in the forum before:
https://lowpowerlab.com/forum/index.php/topic,101.msg334.html#msg334
https://lowpowerlab.com/forum/index.php/topic,671.msg4018.html#msg4018
Please check those threads for more details. You should provide 3.3v+dropout (typically about 0.2V) to VIN, and NOT to 3.3V pin.
Quote from: Felix on November 08, 2014, 06:52:07 PM
If you're running through the 3.3V regulator that is the problem. This was discussed in the forum before:
https://lowpowerlab.com/forum/index.php/topic,101.msg334.html#msg334
https://lowpowerlab.com/forum/index.php/topic,671.msg4018.html#msg4018
Please check those threads for more details. You should provide 3.3v+dropout (typically about 0.2V) to VIN, and NOT to 3.3V pin.
Thanks Felix! I searched but apparently not well enough :) Second topic describes it pretty well!