LSM6DSO CS pin config for I2C mode

[engineer]

Hi - I intend to use the LSM6DSO chip in I2C mode. Can you let me know if the CS pin can directly be pulled to VDD or needs resistor to VDD? IF so what may be recommended value/

[Eleon BORLINI]

Hi @engineer​ , it's better to place a pull-up resistor between the CS and Vdd (better if you use VddIO), but consider that usually the CS pin is driven by the MCU without pu or pd resistors. Regards

[engineer]

Hi Eleon - Thanks for the answer. I want to use the chip in the simplest configuration - via I2C only. With this in mind, I will tie VDD and VDDIO to main power supply. Now the datasheet says CS needs to be 1 for I2C to be enabled. What is the best pu for CS considering 3v supply ?

[Eleon BORLINI]

​Your configuration is ok, a typical R_pull_up value is 4.7kOhm. Regards

[engineer]

Hi - I tried the configuration and it seems like there is a high current consumption(300uA) when VDD and VDDIO are tied and a 4.7k pu is connected between VDDIO and CS. The current graph looks something like this:

When I only use VDD to power the chip(no VDDIO, no pu), the current seems to be in line with expected value (3.5uA):

When only VDD is tied to VDDIO, there seems to be similar high current:

Can you please advice on what may be happening? My intention is to simply use the chip in I2C mode.

[S.Ma]

I guess Vddio is to define the digital pin levels when differing from the internal analog block.

If I2C, you also need no pin is floating, so put pull-ups on SDA and SCL and the pin selecting the slave address.

Make sure per the spec your Vdd and Vddio are in the normal range (some are only 1.8V, some require VddIO to be higher than Vdd etc...)

What's the power consumption is CS is 0 Ohm to VddIO?

[Eleon BORLINI]

Quite strange... but I agree with @S.Ma​ , please try also to separate Vdd and VddIO if possible for you and check what happens if CS is just pulled directly to VddIO. Regards