ADXL355 Latch-up condition

Dear ADI support,

 

We have been using ADXL355BEZ in our condition monitoring (vibration transducer) products for a while, we’ve sold about 1000+ of them now.

 

We recently discovered that some of them fail strangely – they report a near-zero vibration (the AC part) - after experiencing a period of over-range high-frequency vibration. We initially suspects our firmware might have bugs, but after some research, we are now quite confident that it’s caused by the defects of ADXL355.

 

We know that ADXL355 has over-range protection mechanism when experiencing excessive accelerations. When activated, the output will be pulled towards midscale in order to protect itself. This is acceptable. But in some rare cases, this condition will persist even after power is re-cycled. The only way to bring the device back to normal is to tap it (or knock it, if you will) with a screwdriver or something.

 

While in latch-up condition, the ADXL355’s output consist of a fixed DC acceleration (in our two cases, it’s around -5g in x-axis. (we didn’t investigate other axis). On top of that, there’s also a high-frequency (around 1.6Khz) AC content, measured around 3.9g rms.

 

As I said previously, the condition is only cleared when external shock is applied. We did not try issuing self-test command. We’ll investigate more if you need more information. I’ll keep you up to date.