Whats the difference between these three breakout boards for the ADXL345 Accelerometer?

Question

I would like to use the ADXL345 in a schematic im working on right now, but as there is no typical/minimal circuit provided within the datasheet i got stuck.

I did a bit of research and found three different breakout boards, where two of them seem to be quite similar, the third one seems completely different:

1: http://www.watterott.com/de/Breakout-Board-ADXL345

2: http://www.sparkfun.com/products/9885

3: http://www.ebay.de/itm/ADXL345-3-Axis-Digital-Acceleration-Gravity-Tilt-Module-For-AVR-ARM-MCU-Arduino-/171532017402

I do have the third one right here and it works quite well when hooked to an arduino, but as i am looking to combine it on one custom pcb i am wondering if it would work out if i use the ADXL345 like in breakout-board one or two.

I think that the third one differs as it features an 6206A labeled ic. After some research it turns out it might be a voltage regulator, which does make sense cause its the only one board that supports 5V for supply voltage. But it surprises me that i can drive the i2c at 5V without any issues although the adxl does not seem to be 5V tolerant.

So what components would you suggest me to use in my Design (my design runs on 3.3V so no need of a regulator) and how do you think could these differences between the breakout board affect the accuracy of the accelerometer?

Answer 1

As you've figured out, these boards all do the same thing electrically. The relevant pins of the part are brought out, as well as the manufacturer-recommended grounding and bypass capacitors. (It would be wise to read the datasheet and double-check these yourself.)

If you are going to use the ADXL345 on a multiplexed SPI bus, you need an additional logic gate. See the datasheet or previous discussion: https://electronics.stackexchange.com/a/34586/411

One consideration unique to accelerometers is their sensitivity to the mechanical mounting of the circuit board. If you mount only the edge of the board it can resonate like a tuning fork and affect the measurement. Or if you mount it with something like foam tape it can absorb high-frequency vibrations, for better or worse. The datasheet has a section discussing this. So maybe the choice of physical mounting arrangement will lead you to choose one board over another.