BLE is getting disconnected when the motor is turned on in NRF52832 circuit.

[Sweety]

Hello, I have designed a custom board with NRF52832 IC which controls vibration motors. And I am turing on vibration motor from n-channel mosfet as shown in the image below.Gate Signal to mosfet is set by NRF52832 IC. I observed when motor is switched on for approaximately one minute, BLE is getting disconnected.

NRF52832 IC is powered from 3.3V And vibration motor is powered from 2S LiIon battery.

What might be the issue? Please help me in this regard.

[AmbystomaLabs]

I think probably RF noise is causing the problem. Most vibe motors are simple brushed motors and generate gobs of RF noise. All that local noise, a lot at 2.4GHz by the way, will eventually cause the ble stack to give up. There could easily be so much noise that the advertisements aren't getting through and most if not all of the ble channels will show as in use.

For this reason, normally a comprehensive noise filtering circuit is used to power the vibe motor. You can't just hook it up to power and have mosfet switching it.

Most designs employ a parallel zener to clamp the turn off spike, then a series resistance to limit the turn on surge and finally all the power and ground come through LC networks.

In addition to radiated noise, most of that garbage is probably propagating through your switchers to Vdd_nRF causing similar issues in the analog circuits of the nRF which can be affected at lower frequencies and at RF. Finally the noise can cause momentary gpio fluctuations that can be interpreted by the nRF as pin asserts, reset indications,etc. all of which could lead to a device reset.

The bottom line is you need to hook up the vibe motor correctly and get rid of the noise.

[AmbystomaLabs]

Yes, just follow the guidance in the best practice article.