Can I go below 1uA during deep sleep? - Page 1
Forum section: electronics / projects

author: sgpee
author_rank: Contributor
timestamp: November 25, 2010, 10:25:42 am
content: Fellow masters,I like to design a board that works with a 1.5AAA battery. The processor and some of the other ICs require 3V so, I will have to use a DC-DC converter, that is no problem. The problem is, my device will be off 99% of the time and leakage is not fun.So, I am looking for a solution that would get the power consumption of the system during off mode less than 1uA @ 1.5V.I have an on-off button but that is not mechanical, so I cannot cut off the power mechanically, I need to do it electronically.For example, I looked for a DC-DC converter with a button press/bounce logic to turn on the system (where I could turn off via uP). I also looked for a 1.5 ultra low power uP that I can use to control some switches so that I can cut off the power to even DC/DC. (no such uP exists, at least based on my research) Neither these approaches proved useful.Now, I am at a loss and open to suggestions.thx, sgpee

author: CryptLordGR
author_rank: Contributor
timestamp: November 25, 2010, 10:58:02 am
content: why not use 2 1.5V batteries so that you dont need the DC-DC converter and use the the stand by mode of the uP. MSP430 is very efficient in battery when programmed correctly for less consumption. It is 0.4uA in Standby mode when powered by 2.2V in the worst case if powered by 3 it can't pass the 1uA

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: November 25, 2010, 12:22:08 pm
content: Why do you think you need to get below 1uA?Nominal capacity of an AAA is about 1000mAh, so 1uA corresponds to a life of about 100 years!Unless you're using small coin cells, anything under 10uA is completely insignificant.

author: tinsmith
author_rank: Contributor
timestamp: November 25, 2010, 10:35:32 pm
content: SNUPI (PDF) is using the MSP430 to get an estimated 1.5 ?W during sleep (i.e. 1 ?A @ 1.5V). That level is achievable, and probably more than adequate if you just want to minimize leakage. But I don't think you're realistically going to beat it without custom logic.

author: EEVblog
author_rank: Unknown
timestamp: November 25, 2010, 11:59:29 pm
content: There are several boost converters that use less than 1uA in off mode.The MCP1640, AS1329, and TPS61103 are several examples.But I agree with Mike, why the concern?Dave.

author: sgpee
author_rank: Contributor
timestamp: November 26, 2010, 01:12:09 am
content: Concern is the size of the device... The Coins are good but they don't give me the lifetime I need, I can live with a 1 AAA but not two, hence the concern. Regarding why target 1uA, simple 95-9% of the time the device is off, and when it is on, it consumes a lot of battery, I am really trying to make sure I can reduce the power consumption such that it can live for a year.I will study the boost converters Dave suggesting and follow up with questions if any.Thanks guys,sgpee

author: EEVblog
author_rank: Unknown
timestamp: November 26, 2010, 02:50:10 am
content: Quote from: sgpee on November 26, 2010, 01:12:09 amBut as Mike pointed out, 1uA standby current consumption represents 1,000,000 hours or greater than 100 years for a AAA battery. That's 10 times more than the expected battery life and hence self discharge rate.There is simply no need for this level of performance when using a AAA battery. Even 100uA standby would give you more than a full year of standby use. Many DC_DC converters have quiescent operational current draw less than this, so maybe no need for an on-off switch, you might be able to leave it running and simply put the micro to sleep.The MCP1640 for example uses only around 20uA with no load, which is effectively what a good micro in sleep mode will be.Dave.