SOLVED: Voltage regulator pads were backwards on PCB.

I've been working on making a 5V power supply for an Axiomtek PICO831 motherboard, and I have decided to use the Texas Instruments LM2576SX-
5.0 switching voltage regulator. I then built the following circuit based off of the recommended circuit in the datasheet:

Where U1 is the switching voltage regulator and all of the parts meet the specifications put forward in the datasheet. I also added an additional low pass filter.

The issue I am having is that when I hook it up to a 9.6 V LiFePO4 battery with no load it immediately causes C2 to fail and become a short. This in turn triggers the short circuit protection on the battery and cuts power to the circuit. I have already fried two 100 uF capacitors and have no idea what is wrong. This is particularly perplexing considering it is exactly what is recommended in the datasheet.

Any help is greatly appreciated!

 

Either the polarity is incorrect or the applied voltage is greater than the rating of the capacitor.

 

Incorrect polarity was the cause of a previous failure that I have since corrected. It is not what is causing this failure. All the capacitors are rated for at least 25 V.

 

There are some major layout issues and particular info about bypassing: www.ti.com/lit/ds/symlink/lm2576.pdf#page=15

You want a low ESR cap. Check the specs: e.g. http://www.mouser.com/ds/2/315/AAB8000C211-1099531.pdf
isn't C2 supposed be around 20 uF?

High ripple will kill a capacitor.

 

High ripple will kill a capacitor.

Remember this capacitor is killed "immediately" and with no load on the supply.

 

There are some major layout issues and particular info about bypassing

My board is compact by necessity, with all components practically right next to the IC. I believe that was the biggest layout concern the datasheet mentioned. The only special considerations for the input capacitor appear to be related to low-temperature operation.

isn't C2 supposed be around 20 uF?

I do not believe so. From the datasheet:

8.2.1.2.4 Input Capacitor (CIN)

An aluminum or tantalum electrolytic bypass capacitor located close to the regulator is needed for stable operation. A 100-μF, 25-V aluminum electrolytic capacitor located near the input and ground pins provides sufficient bypassing

 

Ahhh, I figured it out. I accidentally had the pins defined backwards in the Eagle device, which lead to them being printed backwards on the board. I imagine that would cause all sorts of issues - in fact I wouldn't be surprised if the voltage regulator itself is bricked.

I feel kind of stupid for posting this thread only to resolve the issue myself. Moreover, because I didn't provide the board layout, noone could have pointed it out for me no matter how long this thread stuck around. Sorry about that!

I really need to make a list of things to check when a circuit doesn't work...

 

Hey, don't feel bad at all. I used to help people in their programming class by not even paying attention. I just asked them about their program and they found the error themselves.

 

Footprints is one of the first items on a PCB review checklist.