sim908 turn of automatically problem

[engineer khan]

i have designed a small circuit containing pic mcu and sim908 the circuit works well but after some second it goes off automatically the mcu and rest of circuit work perfectly but sim908 turns off, i have connected 1000uF on VBAT of sim908, supply is best voltage 4v is provided antennas connected ,disconnected in every case it does the same why?

please reply

 

[Kurenai_ryu]

current, does your power supply the required 2A as the datasheet stated?

I had a similar problem with a SIM900 (same company but without gps) the SIM900 kept turning off when executing some heavy current tasks, like Rx a Incoming call, or Initiating a Data transmition... truth is my power supply was capable of supplying 700mA with 1.5A spikes tops, after that the voltage dropped too much and the 1000uF wasn't enough to keep the voltage at an acceptable range enough to keep the SIM live....

When I developed my project I used a USB port from a computer, it was said that it delivers only 500mA tops (USB 2.0) but in reality my computer didn't have any current controller so, it was connected (with a fuse) to the 5V rail power of the PC (which can deliver a lot of Amps) and that's why I didn't detect this behaviour before using and independent power supply.

 

[sreepss]

Please clarify which power supply you are using?? Is it linear or switching power supply?