In our first enginnering samples, the EC25 module does not output the 1.8V from VDD_EXT (pin 7) after 3.9V power suppled to VBAT pins.
Does anyone know the cause of this problem ?
W.K. Tam
1 Like
Is PWRKEY pulled down to perform startup? If VDD_EXT does not output, the module will definitely not boot up properly.
If you execute PWRKEY to pull it down, and there is no output from VDD_EXT, it is recommended to use an oscilloscope to measure the waveform and see if there is any change in VDD_EXT.
It is also possible to measure the diode characteristics of the VDD_EXT pin to determine if the pin is damaged.
Thanks. After execute the PWRKEY pulling down, it works.
We are facing another problem. We cannot detect sim card. We got error SIM not inserted.
I checked the electronic circuit. The connection is right.
Does any expert know the cause of this problem ? How to fix it ?
Thanks.
You use AT+CFUN=0, then AT+CFUN=1. After executing the AT command, use an oscilloscope or multimeter to measure whether there is voltage output at each pin of the SIM card. If there is no voltage on any pin, the module is abnormal.
Please note that the output power time of each pin will be very short. Only when the communication between the module and SIM card is completely normal, can all pin signals be continuously output.
If there is voltage, it indicates that the card is abnormal or the connection between the card and the module is abnormal.
Hello,
I am experiencing an issue with several Quectel EG25-G modules. Out of a batch of 200 boards, 7 modules fail to start properly, even though the hardware configuration is strictly identical across all of them.
Hardware Context:
VBAT_BB and VBAT_RF supply**: Stable at 3.8 V
USB_BOOT**: 0 V (pulled to GND via pull-down)
PWRKEY**: Low pulse at 0.8 V for 500 ms, then returns to 1.38 V
RESET_N**: 2.3 V (high level, left floating)
VDD_EXT**: Measured at ~2 mV (instead of the expected 1.8 V)
- Module current consumption: ~100 mA
Tests Performed:
Verified power-up sequence and PWRKEY timing/logic levels
USB_BOOT confirmed at 0 V → module is not in DLOAD mode
RESET_N left floating, measured at 2.3 V → no active reset
VDD_EXT remains at ~2 mV, whereas a running module typically outputs 1.8 V
All components connected to VDD_EXT (pull-ups, buffers, UART bridge, etc.) have been removed to rule out any external short or overload.
Additionally, the USIM is not detected — could this be a consequence of the module not powering up correctly?
Do you have any explanation for this abnormal behavior?
Is this a known issue affecting certain batches of EG25-G modules?
Is there any recommended test procedure to confirm whether the module is properly booted or a method to force its power-up?
Thank you in advance for your support.
Best regards,