ISM330DHCX - Can you leave SDx and SCx signals floating in Mode 1?

[SPhil.3]

We are laying out a prototype board with the ISM330DHCX in which we would like the option of using the part in Mode 1 or Mode 2. The board will have zero ohm resistors that will allow the other sensor to either be connected directly to the ISM330DHCX via the SDx and SCx lines (Mode 2) or connected to the main I2C bus (Mode 1). If we decide to just connect the other sensor to the main I2C bus and run the ISM330DHCX in Mode1, the SDx and SCx lines will be floating. Is leaving the SDx and SCx lines floating an issue?

Thanks for you assistance -

[niccolò]

Hi @SPhil.3​ ,

in mode 1 the SDx and SCx pins must be tied to either GND or Vdd_IO.

by leaving them floating you risk to trigger internal noise to other lines.

I can suggest to use a simple jumper that can be manually turn to GND/Vdd (your chioice) when using mode 1 and to the other sensor line when using mode 2.

do you think it would be feasible?

Niccolò

[SPhil.3]

Thank you for the quick answer.

Is it ok to connect the SDx and SCx lines to Vdd_IO using 4.7K or 10K resistors when in Mode 1?

In the attached schematic snippet, we will not populate series resistors R46 and R47 when in Mode 1. That will leave SDx and SCx pulled up to Vdd_IO through 10K resistors.

Thanks for your help -

[niccolò]

Hi @SPhil.3​ ,

having the resistors there as pull-ups is not technically wrong, but there could be some issues with power consumption.

I would advise to use the resistor needed by the other sensor as pull-up, so that you don't have to add it later.

Niccolò

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