LIR2450 Footprint and Dimension Drawings
I'm working on a couple designs that I want to be battery powered and USB-rechargeable. I'm not excellent with low power design, and some designs simply use a relatively high amount of power when active (on the order of 50 - 100mW), so no matter how good my standby power is (on the order of 100uW), I need a battery with decent reserves. It also needs to be small.
Therefore, the coin cell. Pretty much no other option that I know of.
Unfortunately, Digikey was sparse. They had the right size, capacity, and max discharge values for non-rechargeables.
A bit of googling, however, found me with the LIR2450 (lithium rechargeable version of the CR2450), as well as not one but two reference designs: Chasing 'trons
(found via Hackaday
, which misspelled it as the LR2450), and the fabrickit Coin Cell Brick
The LIR2450 has what I need: relatively small height, a 100mAh nominal (120mAh typical) capacity, and at least a 50mA discharge rate. Perfect. Buy it on Ebay.
So now I had the reference design to charge and use the LIR2450 at 3.6V or boost it to 5V. There were two more challenges: buy the battery, and find a footprint.
I wanted to use the version of this battery that already had leads. I didn't want to use the bare battery and the standard clip for it because it was too big, and didn't offer the opportunity to put devices underneath.
Unfortunately, my only economical source for the battery ended up being ebay. I got them there for around $3/each. Other sources sell them for around $3.50 plus shipping. Sparkfun's LIR2450 comes bare with no leads attached.
And of course, nobody had a footprint, except Fabrickit. I'd have to trust them because the shipping times were so long, I couldn't afford to wait for the batteries to arrive.
But today, I get to upload a dimension drawing and photographs. Now you can be sure that the convenient package you get on ebay will be usable for you. (Part 2 will show me actually putting the battery to use). You can easily create a footprint for your favorite EDA tool using these dimensions.
Meat and Potatoes
Here it is! Actual size specifications! A poor datasheet courtesy of http://www.powerstream.com/p/Lir2450.pdf! And an ebay link.
I apologize for the not-very-good dimension drawings. I used the free online version of autocad to do them.
Dimensions in plain text
- 24.5mm outer diameter (top yellow part), 22mm inner diameter (bottom silver part)
- 5mm tall coin cell
- 4mm wide tabs at either end
- Long tab is 5mm tall
- Triangular sections are 2mm tall, and taper to 0.75mm wide
- Pins are 0.75mm wide and 4mm tall
- Pins are 0.20mm thick
- Make drills 1mm in diameter, 12.25mm away from center on horizontal
Disclaimer: If any of the data here is wrong, I'm not responsible for your broken devices. There's no guarantee that this works. But if you find a bug, tell me about it!
Disclaimer: I'm also not responsible if you hurt yourself in some weird way with this article. Don't eat the batteries. Don't try to charge them with mains power. Don't solder your fingers.
September 20, 2013