AnsweredAssumed Answered

reduce input noise to ADXL001 (change C1)

Question asked by JMGL on May 13, 2013
Latest reply on May 14, 2013 by neilzhao

Hello,

 

First of all, I would like to apologise if my question is naïve, but electronics are far away from my main expertise. I am designing a small circuit similar to EVAL-ADXL001 but with a different geometry (I need to fit it into a small space). I am worry about noise that can be generated between my source and the ADXL001 because I have to move long cables close to a magnetic circuit. I wanted to set a low pass filter right before the VDD/VDD2. My problem is that, if I use the capacitance that is recommended in C1 (0.1uF) the resistance that I have to add is very large, and I cannot find a geometrically small resistance (but large in resistivity) that can stand the 9mA of maximum current of the input.

 

For instance, if I want to install a 50Hz low pass filter with the 0.1uF capacitor, I would need a resistance of 30kOhm. For this resistance to stand the 9mA, it would have to be certified for 2.5W. Those resistors are larger than the accelerometer itself.

 

I was wondering if there was any limitation in increasing the capacitance of the capacitor between VDD/VDD2 and GND. If, for instance, I could use a capacitor of 1uF instead of 0.1uF (which are as small), I could easily find a small resistor of 3kOhm certified for 0.25W.

 

Thank you for any comment that you can add.

 

Regards,

 

JMGL

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