SF Pro RF: unreasonable current draw

Components & Accessories Power
1

I’m struggling to figure out why my Pro RF is drawing so much current. I’d like to use it in a battery-powered application, but I’d need to cut the current draw dramatically.

I put the chip on a USB power monitor (with 10 mA resolution) while connected to TTN, and it was drawing a whopping 130 mA. Not sure if the radio is truly put to sleep, I did a test with a variety of boards, blink, and LowPower:

SF SAMD21 Dev:

  • blinking: <10 mA

  • sleeping: presumably <<10 mA

Adafruit Feather M0 + LoRa:

  • blinking: <10 mA

  • sleeping: presumably <<10 mA

  • running lmic (LoRa) example: < 10 mA (with the occasional spike for the radio)

SF Pro RF:

  • blinking: 60 mA !!!

  • sleeping: 10 mA !!!

  • running lmic library: 70 mA !!!

I’ve looked over the schematics and other than the LEDs, which should draw a handful of mA at most**, I don’t see what could be drawing the current.

Anyone have any idea why this is and what I can do about it? This is a cute, little board, but useless for any practical, battery-powered application in its current state.

Thanks.

**Not sure why SF puts a status LED on a battery-enabled board – seems a tad silly – but I can remove the physical draws, if needed.

2

Are you putting the radio to sleep with not in use? I think if you don’t explicitly put it to sleep, it sits there and listens.

Are you taking advantage of the sleep/low-power functions of the microcontroller? In my experience, they don’t sleep unless you tell them to.

3

For the installation, I’m using the lmic library, which puts the radio to sleep.

But I get high currents when just running blink, which doesn’t even touch the radio. Same with sleep. my guess is there’s something with the LiPo manager chip that isn’t right.