I have bought SIM808 module, everything working fine. All AT commands are giving expected response, i'm accessing it through hyperterminal. My problem is that whenever i make or receive a call or SMS , GSM gets restarting.(I can able to make/receive call, getting ring/alert for small period of time and then interrupt). But there is no Under or Lower voltage power down or warning. I have tried with DC power supply of 5V/500mA , 5V/1A and 5V/2A. What might be the reason ? Please help. extra info : It has one LM2576S voltage regulator in-built.
Check the datasheet and I think you will find you need 3 amps peak. It requires this peak current when you make a call or send a text/sms.
Use a 5A power supply and that should solve the problem.
I have never tried it but "super capacitors" might work, providing the extra power when its needed, it depends how long you need the 3A for.