I am observing large noise on ADXL375. I am running it on 4 MHz over SPI. I am using 2 ODRs: 100Hz and 800 Hz.
On 100 Hz, the noise should be under 50mg as datasheet gives 0.005 g/sqrt(Hz), but its closer to 100mg.
On 800 Hz, the noise should be under 141 mg but its close to 300mg.
SPI cable length is just 10cm, which isn't long.
What is the reason for this? How to reduce it?