LIS3DH Single/Double Tap Detection Current Consumption

[Dillah]

Hi,

We notice that LIS3DH accelerometer has multiple mode which can be utilized to be used on low power mode for single/double tap detection.

Does single/double tap detection increase the current consumption stated on the data sheet/design tip?

https://www.st.com/resource/en/datasheet/lis3dh.pdf

https://my.st.com/content/ccc/resource/technical/document/design_tip/group0/d6/1d/5f/b0/3c/6e/47/27/DM00564061/files/DM00564061.pdf/jcr:content/translations/en.DM00564061.pdf

Thank You

[Eleon BORLINI]

Hi @Dillah​ , the typical current consumption contribution of a digital embedded feature such as the single/double tap detection (that includes a couple of threshold comparisons) is less than 1uA, a fraction of the overall standard current consumption. Regards

[Dillah]

HI Borlini,

Thanks for the information.

Is there any recommendation on minimum data rates for acceptable double tap performance?

Noted that tap threshold will be acquired by manual testing on the unit.

We want to use as low current consumption as possible.

[Eleon BORLINI]

Hi @Dillah​ , sorry for my delayed answer. From the LIS3DH app note AN3308 (p. 31), the recommended accelerometer ODR for single and double-click recognition is 400 Hz or higher. You can however try to lower this ODR and check if the feature is working in your specific application case, if the low current consumption is a major request. Or you could try with a more recent sensor like the LIS2DW12 to get lower power consumption on double tap application. Regards

[Dillah]

Hi @Eleon BORLINI​ .

Currently we are working in 3V environment, and we are computing power budget.

However we can not find LIS2DW12 averaged current consumption on 3V voltage supply.

I would ask if you have similar data to current consumption vs voltage supply?

Thanks

[Dillah]

Hi @Eleon BORLINI​ ,

Thank you for those information.

Our power budget on accelerometer is around 3uA in 3V supply voltage.

After some evaluation, we will try to use 25Hz or 50Hz ODR as shown on below image.I would ask if you have similar data of current consumption in 3V power supply for highlighted mode?

Thanks

[Eleon BORLINI]

@Dillah​, of course going in LPM will help the power budget requirements. The curr cons for 3V in LP1 at that ODRs is about 2.5uA with ODR 25Hz, so this is the condition in your case. Please note that the resolution lowers from 14-bit to 12-bit, you should have to check if you can detect the single/double tap in a good way. Regards

[Dillah]

HI @Eleon BORLINI​ ,

Thanks for the info.

We will try to test the double/single tap sensitivity of said setting.

[GGabi.1]

Hi @Dillah,

 

Did you have the opportunity to test the current consumption putting the sensor in low power mode? 

If so, what was the averaged result?

 

Reading from the datasheet I'm afraid that sensing single/double tap is only possible running the sensor in high performance mode.

 

Thanks in advance,

[Dillah]

Hi @GGabi.1,

The current consumption are consistent with what it shows in the datasheet.

Our development was limited by current consumption limitation, so i only used the lower ODR rates to keep the current below 5uA on average.

 

Thank You.

[GGabi.1]

Thanks @Dillah for your fast answer

 

So, are you telling me that you did successfully the tap detection implementation with an average of current consumption of only 5uA? And it worked well?

I guess that as you cannot set the wake-up interrupt of tap detection in low power mode, then you have needed to use a fixed threshold to wake-up and then change the operative mode of the sensor to active mode, changing the ODR sampling rate. 

Is my assumption correct?

 

Thanks in advance