EC200T Periodic reboot issue


I have a new design using EC200T-EU. The GSM starts, I receive RDY, I can send a couple of AT commands but after ~10 seconds it stops responding and reboot.
I checked power stability, 4.0V on main supply is OK.
The internal 1.8V drops when it reset, otherwise stable.
RESET# signal is not used, up at 1.8V.
PWRKEY# signal is driven by an open collector, stable at 3.6V.
Revision : EC200TEUHAR02A04M16
No SIM connected

Any ideas ?
I’m used to GSM module designs but that’s the first time I see this kind of behavior.

Best regards,

Dear Sir,
Thanks for your inquiry in Quectel forum.
About your issue, could you help to monitor the wave form of VBAT, RESET, PWRKEY pins to check whether there have any abnormal phenomenon. Normally, the module will not restart automatically. Thanks!

Hi,Have you solved this problem?I have the same problem as you,can u help me?

It is better to check the stability of the power supply for module. Thanks!


Yes I’ve solved this problem.
I started this project when the Quectel HW design guide was in revision v1.0. In this first revision, they recommend to put a 33pF decoupling capacitor on pin 118 WLAN_SLP_CLK.
I discovered that the board was stable when removing this capacitor.
After discussion with Quectel, they told me that the new Quectel HW design guide v1.1 recommends to keep pin 118 open.

Best regards,