Unable to get proper output from Gyroscope

NevadaMark Hi, can you help us in figuring out the issue?

nimejia Hi, can you help us out?

Hi, 

Could you please confirm the measured VDD, VREG, and CP voltages on each board and share the schematic and assembly/solder details that you applied?

The gyro relies on the charge pump to generate the required high voltage for proper operation. If CP is not close to the expected about 31 V, the rate output can look incorrect even though SPI read/write is working. Reading fixed registers (such as ADI/MEMS/DEVICE ID) confirms that digital communication is OK, but this does not guarantee that the gyro itself is operating correctly.

Thank you, hgavcar 

Even on the working device, 38V sounds really high. I am wondering if we should look at the voltage rating on the capacitors in their circuit.  For example, we have found that X7R capacitance can be heavily dependent on the ration of the applied voltage to the rated voltage.  

Hi NevadaMark and hgavcar ,

I will provide the schematics and other assembly/solder details shortly. PFB other details below:

C_p is 1 uF 0805 50V X7R 10%

Board 1
CP = 38.4V, Vreg = 1.878V, Vdd = 3.324V

Board 2
CP = 25V, Vreg = 1.88V, Vdd = 3.33V

Board 3
CP = 38.4V, Vreg = 1.882V, Vdd = 3.31V

Thank you! Just for your information, our team is supporting a weeklong event, so our next round of responses might be delayed. 

Hi hgavcar and NevadaMark ,

I went through the assembly report and found that Baking temperature used was +125°C for 9hrs. Could that be the reason for the above mentioned behaviour?

Absolute Maximum Rating section of datasheet mentions +105°C as storage temperature.

Also, FYI, we have made few boards earlier with the same schematics and BOM, however, from a different vendor and those boards are working fine, Cp voltage on that board is 31.9V.

Hi usr 

Thanks for the additional information.

VDD and VREG look nominal on all boards, so the digital and low-voltage domains appear to be operating correctly. The main concern is the CP voltage: under normal operation it should be around 31 V, but the measured values vary significantly (25 V to 38 V), indicating inconsistent charge-pump behavior.

Since the same schematic and BOM worked correctly on earlier boards from a different vendor (CP ≈ 31.9 V), this points more toward a manufacturing process (soldering/baking) or assembly-related effect rather than a design issue.

The Cp capacitor itself seems to be rated up to 125 °C, so it is unlikely to be the limiting factor. However, the ADXRS290 storage temperature is specified up to +105 °C, and extended exposure above this limit could potentially affect analog performance (note that short excursions above 125 °C can occur during soldering as recommended in datasheet). I will re-check the sensor qualification documentation to better understand how the storage temperature limits are defined and what margin exists beyond the datasheet specification.

Could you please confirm how long the sensor was exposed to 125 °C during the bake process?

Hi hgavcar ,

Baking temperature used was +125°C for 9hrs.

Hi usr ,

First of all, wishing you Happy New Year!

I’ve reviewed the ADXRS290 qualification documentation and prior test results, and the +125 °C / 9-hour baking condition does not appear to be an issue based on those findings.

You mentioned that the same schematic and BOM worked correctly on earlier boards from a different vendor, so this seems more likely related to a manufacturing or assembly process difference rather than a design issue. Do you know of any differences in the soldering, baking, or assembly processes used by the previous vendor compared to the current one? 

As another potential aspect to look into, under normal operation the CP voltage is expected to be around 31 V, and a capacitor-related effect could influence this. As NevadaMark  previously noted, X7R capacitance can be strongly dependent on the ratio of applied voltage to the rated voltage. Since C_P is currently 1 µF, 0805, 50 V, X7R (10%), would it be possible to try an alternative capacitor option (e.g., higher voltage rating or different dielectric) and see whether the CP voltage behavior changes?