[TriEmbed] Ground Confusion

Charles McClelland chip at mcclellands.org
Wed Apr 30 18:38:06 CDT 2014

To all, 

I have been looking at a way to improve my battery life for my trail traffic counters.  I am currently using a linear power supply and with Sleep and other power savings methods, I can easily get a week on battery with 4 AA batteries (my board operates at 3.3V with very low average current and I estimate a 150mA max).

However, I want to do better: 
	- For the SD Card sensor - to go a week on just three AA cells
	- For the wireless sensor - to go 6 months with a 6V lantern battery

I started looking at Texas Instrument’s buck-boost switching power supply chips and using their WeBench tool, designed this circuit.

What is better, TI sent me three of these chips for free!

My question is in how I am translating their schematic into an EAGLE file I can ask OSHPark to make for me.  The schematic has both Control Ground and Power Ground.  And the design report says "Use a common ground node for power ground and a different one for control ground to minimize the effects of ground noise. Connect these ground nodes at any place close to one of the ground pins of the IC.”

I decided to use a Sparkfun solder jumper which is normally closed to make the connection between GND and pGND.  But do any of you know a better way - or could you take a look at my EAGLE files and tell me if I did this right?

Here are all the files on drop box - https://www.dropbox.com/sh/9qdzturvffr66do/3QMS0SvYHP

Thanks for the help.  If this works, happy to share the design for those who are looking to get more life out of their batteries.

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