I had a couple questions around the acceptable lower battery range for the B404X.
According to the B404X Datasheet:
- VCC is used to supply power to the u-blox SARA-R510S cellular module. The recommended input voltage range on this pin is between 3.6V to 4.2V DC. This can be connected directly to a 3.7V LiPo battery.
We use a 1S2P 3.7V Lithium Ion Battery in our product, which should have a similar functional voltage range, and we and our power architecture is similar to that on the evaluation board. I was wondering why/if 3.6V a hard lower limit?
To me, that would cut into our battery life by more than 40% compared a more typical minimum voltage of around 3.0V. From what I can tell looking at datasheets for chips on the B404X, operation should be normal with VCC down to 3.3V and "possible slight deviation in RF performance" down to 3.0V [per SARA-R5 spec], and VCC should track slightly below VBATT without external power inserted.
Also, I generally tried to follow the B-Series Evaluation Board's power and gas gauge architecture, but I accidentally severed the !FUEL-INT connection to the MCU (effectively would be like removing the interrupt jumper on the eval board, see below.)
Is there anything underlying in the OS that this would affect or would this only be used with more explicit battery level monitoring in application layer? It looks like the gauge is configured to flag the interrupt at 20% SoC, when reading its register with an Aardvark.