Hi. I'm testing various NB-IoT modules for long-term battery operation and stumbled upon the Olimex module. It lists a 120 uA PSM current draw, but the actual module draws about 5 uA in this mode. Can it be reduced from the advertised 120 uA closer to the bare module consumption? Where does that extra ~115 uA go? Do you have any suggestions? Thanks in advance.
It is lost in the voltage regulators and level translators. You can reduce total consumption if using a Li-Po battery to power it. Some more details:
- The BC66 module only has even lower consumption compared to the advertised by BC66 datasheet. In our empirical tests it is between 1uA and 3uA when in PSM mode.
- The rest of the board consumes around 125uA. It is important to notice that is when powered by external power supply.
- If powered by Li-Po battery that consumption is less, around 85uA.
We exhausted many different options for voltage regulators and translators during the design phase and what we picked in the end was with lowest power consumption in mind.
Thanks for the detailed answer. I'm looking at the schematic (https://www.olimex.com/Products/IoT/NB-IoT/NB-IoT-BC66/resources/NB-IoT-BC66_Rev_B.pdf) (is this the correct one?), and I only see an AP1231-1.8V LDO with about 20 uA operating current. The 2 level shifters are about 5 uA each, module 5 uA (worst cases). This all adds up to about 35 uA - there is 50 more uA flowing somewhere, assuming battery operation. It's impressive in itself, but could it go even lower?
Not sure myself, AP1231 should consume 20uA and 2xTXB0108PWR should be 40uA (it is 5uA per side) maybe measure without the SIM card and double check the netlight.
Alright, I order a couple and test myself. Maybe I'll just disable/cut power of the level shifters when testing power. The SIM should already be in the nanoapms range.