Mkr nb 1500 problem with boosting 5V in battery mode

Official Hardware MKR Family MKR NB 1500
1

Hi,
using the MKR NB 1500 I assumed I could boost 5V to the 5V pin when in battery mode with USB cable detached. For this, the I2C-controlled switcher charger/boost converter BQ24195L can be programmed. See example code Arduino_BQ24195/PMIC Boost Mode and respective lib, code line with "PMIC.enableBoostMode();"

However, in battery mode, I can only measure 2V7 at the 5V output. On the other side, I measured an unexpected 5V at the VIN pin, which should not be there due to the pull-down resistor (1MOhm, R19). When I assist this pull-down with pulling VIN to GND with an additional 220kOhm resistor, the 5V1 appears instantaneously at the 5V output pin.

I found this to happen on both of my two boards with nothing else but the battery connected (charged at 3V9).
My question is if this is indented behavior and should I consider this additional pull-down in the circuit or is there something else I miss?

Any help is appreciated. Thanks
bst Matthias

2

Hi
I don't get your issue, not even what you mean with battery mode.
The addtional battery is to feed the power spikes of the modem and for a better antenna performance as well. But IMHO the bat not neccesary. Just power the board with a proper supply on the designated pin - simple as that.

3

Hi,
thanks for your answer. I need to power the board only with the lipo battery ("battery mode" instead of using a USB cable) and I want to supply external circuitry from the 5V pin. With the battery connected, enabling the boost converter to supply 5 volts at the "5V" pin should be possible, right? I used "PMIC.enableBoostMode();" to enable the boost mode via I2C. However, an unexpected non-zero voltage at the VIN pin hinders the boost converter from enabling the boost mode. There is a 1Mohm pull-down at this pin but it is insufficient. An additional 220kOhm pull-down works to pull VIN down and enables a properly boosted 5V output.

This workaround is okay for me, but from what I read so far it should be working without it. So what did I miss?
Thanks again.

4

So you want to power the whole board with that LiPO battery on the designated connector? I don't think that will work. Why dont't you just take a power pack (You need a special one that supply power even with low current demand, regular power packs switches off with just a MKR connected)
I can check which one i use and write it later here if you want (i'm on the job now)

5

This topic was automatically closed 180 days after the last reply. New replies are no longer allowed.