I’m putting together a tiny temperature sensor with LoRa radio (based on STM32WLE5) and I intend to power it directly from a CR2032 3V lithium battery without Vreg. I’m wondering whether I should add something for reverse polarity protection, i.e., me managing to insert the battery the wrong way around.
I haven’t settled on a battery holder yet, and most provide some degree of protection. Maybe that’s enough. Or perhaps using a P-ch mosfet is worth it. e.g.:
I could also use an N-channel version of the same circuit, I haven’t looked at Rds(ON) options vs. cost, etc…
The max expected current drawn by the stm32 is 30mA during TX (I will only use the low-power RFO) and the low-voltage cut-off is around 1.8V. The DMP1045U’s datasheet promises 75mOhm max @ Vgs=1.8V which results in less than 2mV drop.
Am I missing something? Is there a better option? Do I need the gate resistor given the low voltages (the DMP1045U has Vgss of +/-8V and a zener protection diode).