SparkFun Electronics Forum

Use a tantalum.

Leon

Anadian wrote:They shuts down themselfs regulary after 3-4 days.
Within this period they are working just fine, but after that I found them in power off mode (status LED stops blinking),
like when they are turned OFF with on/off button.
If the modules are again turned on via on/off button, they continue to work without any problems,
but after 3-4 days they again shuts down themselfs ...

I have the same problem but status LED blinks every second. I also noticed that after this problem, at+cpin returns "ERROR", like there was no SIM card (electrostatic problem, ESD ?). I need to remove and replace SIM card before restarting...

Someone else would found finally the solution (there is already a capacitor and a TVS) ?

I know this thread is old but I just also wanted to chime in and say that YES, the capacitor has to be very close to the power pins of the GSM module... I also use a L5973D and my 1000uF cap was about 5cm away on the board and it did not work. Only when I wired short 15mm leads to it and connected it to the power pins did the module join the network. I have been searching for this answer for two days! So, that's the solution.