FXAS21002 latch-up due to shock

[jerryking]

I am using the FXAS21002 gyro in a product which I am drop testing. The output of one or more axis (depending on drop angle) will latch at plus or minus full scale after impact. Gyro re-initialization will clear the latch-up. Is this a known phenomenon? Would the use of the rate threshold detection prevent latch-up from occurring and/or detect that latch-up has occurred?

[david_diaz]

Hello Jerry,

Thank you very much for writing.

Could you please help me with the questions below?

1) Can you describe the drop test in more detail? What is the magnitude of the drop (in gs) and what is setup being used? Some basic information on the HW and SW setup would be helpful.

2) Could you send me the output data? I want to see when exactly does it get latched and to what value?

3) Also, how many parts show this behavior?

I am currently looking into our test results and will let you know if this is expected under certain testing conditions.

Best Regards,

David

[jerryking]

Hi David,

See below for comments in red.

Thanks,

Jerry King

Sr. New Product Development Engineer

Snap-on Specialty Tools

19220 San Jose Ave.

City of Industry, CA 91748

Phone: 626-965-0668 Ext. 268

[david_diaz]

Hello Jerry,

Accept my apologies for the delayed response.

NXP has seen this issue before where gyroscopes appear “stuck” at a constant value following a significant shock event. This has been identified as the gyroscope “losing lock”, and the issue is recoverable by simply removing the drive signal from the gyro for a short period of time (NXP recommends a minimum of 10 seconds). The drive signal can be removed by one of two means:

1. Removing power from the part
2. Placing the part in standby mode

Either one of these options will stop the drive signal to the sensor element which will enable it to relax to its resting state. The part can then be placed into Active mode to resume normal operation after waiting for the recommended 10 seconds.

I hope this information will be useful for you.

If I misunderstood your question, feel free to let me know.  I will be glad to help.

Have a great day.

David Diaz.