Author Topic: Different onboard 3.3v LDO  (Read 2854 times)

bruceme

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Different onboard 3.3v LDO
« on: January 07, 2016, 05:06:01 am »
Since I can't use the Oak yet, I'm looking it over.  The specs in the kick rate the 3.3v vreg/LDO at 500ma and the package looks like a SOT-223, probably in the 1117 family, very popular and cheap and yup 500ma.  But what's on the board looks much smaller, SOT-23 and they are typically rated 150ma.  Just a heads up.  It's actually smaller than what I would use to drive an ESP8266, which concerns me, but perhaps this chip uses power better.

defragster

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Re: Different onboard 3.3v LDO
« Reply #1 on: January 08, 2016, 10:51:45 pm »
From KS Oct 30 2015 Update: https://www.kickstarter.com/projects/digistump/oak-by-digistump-wi-fi-for-all-things-arduino-comp/posts/1396055

You should hopefully find the part is as indicated?

Voltage Regulator: The Oak will be using the SPX3819  (Datasheet https://www.exar.com/common/content/document.ashx?id=615&languageid=1033&type=datasheet&part=spx3819) - it is a 500ma 3.3v regulator. Why did we go with this chip: This is one of the very few linear regulators that can - produce 3.3v at 500ma or more, do so even with a single LiPo cell input, and also handle inputs over 5.5v, while producing very clean power. The drawback of this wonderful little regulator is that it is very small (a plus in some ways too) - so it cannot dissipate heat very well. This means that while it can handle voltages up to 16v anything over 7v it can get so hot that it resets - this can be solved with extra heatsinking, careful power management using the options to turn the wifi radio off when not in use and/or sleep modes, or putting a 5v step down regulator in front of it (allowing you to benefit from the clean power of this linear regulator, but stepping down to 5v first to reduce heat).

bruceme

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Re: Different onboard 3.3v LDO
« Reply #2 on: January 11, 2016, 05:07:41 pm »
I love it!  Very smart