Good afternoon,
I'm trying to power an Arduino Pro Mini with 3xAA batteries via an MCP1700 (3.3V version).
The Arduino circuit goes to sleep most of the time; its measured sleep current is about 5 µA (peaks of 10 mA during radio transmission).
When I test my MCP1700 supply on an empty load, it shows a quiescent current of 1.7 µA (as roughly expected from the datasheet).
However, when I power the Arduino, it is constantly drawing 15-20 mA - the Arduino functions normally during that time and goes to sleep.

I might be missing a basic point in the usage of the MCP (this is my first attempt at an LDO regulator for battery power).
I would be grateful for any clues.

 

hi has4,
Welcome to AAC.
Look at these links that explain the Arduino power modes.
https://www.youtube.com/results?search_query=low+power+arduino+deep+sleep+tutorial+

E

 

Thank you for your reply. My Arduino circuit already goes into sleep mode appropriately (5 µA sleep current). However even during sleep, the supply circuit from the battery to the MCP1700 draws 15-20 mA, which I cannot explain with quiescent and ground currents of LDOs.
N.B. Sorry, the problem description in the initial post is ambiguous. Not the Arduino is drawing 15-20 mA, the MCP1700 is.

 

hi,
Have you measured the actual current between the MCP and the Arduino.? while in Sleep Mode.
E

 

Ha, what I thought was a trivial change to the circuit caused the actual problem. I exchanged the 433 MHz transmitter for a different module (and didn't measure the Arduino current subsequently). This has a much higher current draw than the old one. Reverting back to the old transmitter, now I've got an Arduino current of 4.7 µA and total circuit current (from battery through MCP1700) of 6.3 µA.
Thank you, your suggestion helped me locate the problem.

 

Hi,
Thats good news, thanks for letting us know.
E