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How to reduce MintyBoost standby current to 0.5mA
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How to reduce MintyBoost standby current to 0.5mA

by moeburn on Tue Aug 20, 2013 2:56 pm

I have my DMM connected in series with the + side of a 2xAA holder, and the +Vin of the mintyboost, to measure the current draw from my two AAs when the device is in standby mode (unplugged). It's 2.1mA! That seems like a lot for a standby current.

But its because you guys have burst mode disabled using that resistor underneath the IC, to increase DC conversion efficiency at high loads. And that makes sense if you are drawing 100mA, as you can see in this graph, there is a 5% efficiency increase by disabling burst mode. But at anything below 30mA, including standby mode, the efficiency is horrible! And most people will probably be drawing 200ma-500ma, at which point the efficiency gained from disabling burst mode is only 1-3%.

Image
(the graph line that the default MintyBoost v3 kit is "3.3k IT to GND". With this hack, your Mintyboost will be on the "IT Floating" line.)

So if anyone out there has a mintyboost without a power cut switch (like the default kit design), who uses devices that draw more than 200mA (or less than 30mA), you would be wise to bend pin 5 of the lt1302 IC so that it does not plug into the IC socket on the PCB, so that IT is left in "floating" mode, so that it is not connected to that resistor underneath the IC socket. When I did that, my standby current dropped from 2.1mA to 0.5mA.

This way, assuming you have low-self-discharge batteries, your batteries will last 1 year instead of 2 months! Hooray!
moeburn
 
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Re: Large (2mA) standby current - How to reduce to 0.5mA

by adafruit on Thu Aug 22, 2013 10:32 am

Cool hack! We found most people wanted that extra efficiency at high currents - design tradeoffs!

adafruit
 
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Re: How to reduce MintyBoost standby current to 0.5mA

by serwusek on Tue Jun 09, 2015 9:56 am

Wow. If this work as good as it looks it's great thing :D

serwusek
 
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