Thingy:52 replacing MPU-9250 with ICM-20948 - how to change IC voltage?

[Matej]

Hi,

I would like to know how to raplace a MPU-9250 chip with ICM-20948 in a Thingy:52 circuit. 

Let me first state that my electronics engineering knowledge is at hobby level at best. I am currently using a Thingy:52 for my project and got it this far that I want to make my own board now with reduced footprint and most of the sensors removed.

To give myself the best chance of making my board work I copied the Thingy design but I removed everything but:

• NRF52832 chip
• MPU-9250 accelerometer
• Low power accelerometer
• I2C chip
• power circuit
• programming pins
• single color LED

As MPU-9250 chip is deprecated and a bit harder to get I would like to replace it with the ICM-20948 chip. I read the migration guide: http://www.invensense.com/wp-content/uploads/2018/10/AN-000146-v2.0-TDK_Migration_MPU_9250toICM-20948.pdf and it says that the new chip is basically a drop in replacement only the voltage has to be lower at arround 1.8V.

I would like to know:

• Could the new chip be replaced without doing anything? - I believe the voltage on Thingy is 3.3V so probably not - is that correct?
• I believe I read that the minimal operating voltage for NRF52832 is 1.7V - could the entire voltage of the Thingy or Thingy like IC be changed to 1.7V - if yes how and what would be implications of that?
• How can the voltage be adjusted just for the new ICM-20948 chip?

Thanks!

Matej

[Jørgen Holmefjord]

Hi,

Could the new chip be replaced without doing anything? - I believe the voltage on Thingy is 3.3V so probably not - is that correct?

No, it looks like you will need lower voltage for VDDIO for the ICM-20948.

I believe I read that the minimal operating voltage for NRF52832 is 1.7V - could the entire voltage of the Thingy or Thingy like IC be changed to 1.7V - if yes how and what would be implications of that?

Yes, the nRF52832 IC can operate on 1.7 V, but you will have to check if all the sensors you will be using can work at this voltage level.

How can the voltage be adjusted just for the new ICM-20948 chip?

This will require a voltage regulator and a level shifter for the I2C/TWI communication with the sensor.

Best regards,
Jørgen

[Mojo]

It is easier to have both the nRF and the ICM operate at 1.8V.  The ICM voltage range is very limited.  Alternatively there is this board that has both the nRF52832 and ICM-20948 onboard.  Look for the sensor board perk.

https://www.crowdsupply.com/i-syst/blyst-nano