Powering SKU: U111 NB-IoT Unit

haavard.holm

Hello,
Your SKU: U111 NB-IoT Unit is specified to have 5V input. I guess that is for both power and io pins.

I try to operate this device by feeding with 3V. (both power and io pins). This seems to work just fine.

Is it ok to power this device with 3V ? or should this be avoided ?

Best regards
Håvard

felmue

most (if not all) units have a 5 V input. Internally there often is a power regulator to 3.3 V or whatever voltage the ICs used in the unit requires. The signal lines are 3.3 V as they are connected directly to GPIOs of the ESP32 which is 3.3 V too. If the data lines of the IC in the unit have an even lower voltage level shifters are put in place.

The input voltage of the regulator is 2.7 V to 5.5 V. The minimal voltage drop between input and output is about 0.6 V for these regulators. So if you feed it with 3.3 V I'd guess the output voltage to be about 2.7 V.

According to its datasheet the SIM7020 IC has an operating voltage range from 2.1 V to 3.6V so you should be fine. Its data lines are 1.8 V which are then level shifted to the output voltage of the regulator (e.g. 2.7 V) which should still be high enough for the ESP32 GPIOs to recognize properly.

Thanks
Felix