Powering the GPS shield

I have the MKR GPS Shield. On the package it says 5 V input voltage and 3.3V operating voltage. On this page, however, it says input voltage is 3.3 V.
I want to involve it in a system with a non Arduino board, which runs on a 3 V coin cell battery. With its own cell battery I guess the 3.0 V is sufficient for the shield to run. The logic level is assumably 3.0 V if the power source is 3.0 in the microcontroller board as well as in the GPS shield.
I guess the only connections I need are TX, RX and GND, while both units run on their own coin batteries. Or is there something to gain in connecting also the 3V? The GPS shield will mostly be asleep.

@Johan_Ha You need at least 2.6 Volts page 17.

I have similar question.

The product page says 5V, but operating 3.3V although the schematic writes 5V VIN. Can I by-pass the 5V in and use 3.3Volt? If yes which pins I have to connect. Obviously not the 5V.

If you look at the schematic, it does something incredibly stupid.

If you connect with I2C cable, the 5V input is passed to a linear regulator and pass through a diode that drops 0.3-0.4V to power the module with 3.0V, instead of just using regulated 3.3V from the main board.

If you connect as Shield, it draws 3.3V from the main board, and pass through a diode that drops 0.3-0.4V before going to the module.

You need to de-solder and short the diodes array if you want to use 3.0V.

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