Strange temperature offset on custom PCB

Dear developers,

I'm writing in this forum in regard of different behavior seen on custom made PCB against the evaluation board's (MPU9150 EVB rev. A).

I'm developing a temperature compensation algorithm for the accel data for which I ran some temperature tests, applying heat and logging the Accelerometer and Temperature with the InvenSense Universal Data LoggerV1.0 and using the InvenSense ARM Reference Board (EV_ARM_XXAXA_D 2012/JAN. 12).

The devices were configured as follow:

Sampling rate: 20 Hz
Components: Accelerometer, Temperature.
1A | 26 | CONFIG | 00000110 06
(Default values on rest of registers)

These were the results:

MPU9150 EVB rev. A
Reference behavior. Accel data change is inversely proportional to temperature change.





Custom made PCB 1
A sudden change of more than 50 mg at minute 74.






Custom made PCB 2
Accel data change is proportional to temperature. Could this be correct?





Custom made PCB schematic diagram

All capacitors are ceramic X7R.

Top layer PCB

I'd appreciate if you help me identify the problem with our custom made pcb.

Thanks in advance.
Regards.