Power up failure



We have constructed a prototype board for a Q2501 module, but when we plug it on power sometimes the power up sequence fails and the module does not responds to AT commands. This is not happens always and some times the module responds normally to AT commands.

Anybody have an idea what could cause this?



check the voltage of the module it should be above 4 volts at least

we faced the similar problem in the begning


Thanks for the reply

We concluded that the cause of this problem was the linear regulator we used instead of a swithcing regulator like we used to. I suppose the linear regulator was not fast enough on power up to deliver the necessary current.
Has anyboby else used linear regulator ? What were the results ?



No I don’t but…
As long as the power supply can support 2A peaks (!) with voltage above 3.20 volts, it shouldn’t matter if you use a linear or a switched regulator. But, in general, you’ll want to use:
main power --> power regulator cca 4.1V --> backup battery --> capacitors --> GSM module
with wires, MOS transistors or diodes for “–>” as necessary. If you want to replace the battery with capacitors, they have to be VERY large. Even with the battery, we are using 470uF.

You should test if adding the battery helps. Also, make sure you are using a good antenna, it may reduce both EM interference and power requirements. If it works, go back to small antenna.