What is the advanced feature of the pull up at pin SA0 of IIS2DH?

[MVerm.11]

We discovered that the SA0 Input of the IIS2DH of your accelerometers has a very high pull up current.

The pull up is about 40 kOhm at IIC adress select line input. If engineers will use two IIS2DH in there design.

Than the IIS2DH at adres 0x18, means SA0 is LOW, then this chip will draw 10 to 15 times the normal operational current. For an extreme low power device. This is a very special feature from ST.

We would like to know:

What is the feature of this pull up

Why is it not specified in the datasheets?

Wil the IIS2DH soon become obselete?

[Eleon BORLINI]

Hi @MVerm.1​ ,

you are right, the pull-up is about that value for Vdd around 2V.

There could be a solution, however. You could try to disconnect the pull-up by setting '1' the MSB register of the reserved register 1Eh, even if not declared on the datasheet.

-Eleon

[MVerm.11]

Hi Eleon,

Thanks for your fast response.

I did not expect a solution, for this issue, so we had patched the prototypes already to IIC adres 0x19.

Can you give us the register definition of theis reserve 0x1E? So we can test it.

[Eleon BORLINI · Accepted solution]

Hi @MVerm.1​ ,

the solution you chose is the correct one since it is the safest, I thought you weren't able to modify the circuit and/or you had two different devices sharing the same I2C line. I can say you that setting the MSB of that register (1Eh) can disconnect the internal pullup.

In my last reply, I forgot to answer to your question:

>> Will the IIS2DH soon become obsolete?

This product has been committed by ST for the 10-years product longevity, so the product will not become obsolete soon.

-Eleon