Unconnected accelerometer z output

Using Arduino Sensors
#1

Hopefully the last question on this project, Does it hurt to leave the z axis unconnected if I don't use it for anything? It is on a MMA7361 breakout by the way, hooked up to my custom prototype PCB. This is all I can find in the datasheet for the chip itself,

"8. 10M? or higher is recommended on XOUT, YOUT and ZOUT to prevent loss due to the voltage divider relationship between the internal 32 k? resistor and the measurement input impedance", it doesn't say anything about unused outputs. http://cache.freescale.com/files/sensors/doc/data_sheet/MMA7361LC.pdf

I can run a trace to an unused analog pin (last one on the whole 328), just wondering if I need to, or put a pulldown (10M) to ground, a lot less trouble.

I have been running three boards with z freefloating for a couple of weeks, one a couple of months with no problems, but want to be sure before I order my first batch of final boards.

By the way, many thanks to you all who have helped me here, and to others that have posted questions and answers galore that I have learned from. This is a great resource for beginners in Arduino like me. TomJ

#2

Yes, you can safely leave the Z output unconnected. You could connect a 3.3nF capacitor between the pin and ground as shown in the datasheet, but it almost certainly isn't necessary because it is unlikely that the output feeds back to anything internally in the chip. You definitely don't need a pulldown resistor on that pin.

#3

Thanks dc42, The breakout board has caps to ground on each output so I should be good there. TomJ

#4

In general unconnected outputs are not an issue - unconnected inputs can be. This is especially true of CMOS logic inputs which in general should always be connected (unless an internal pull-up/pull-down is provided). Failure to connect CMOS inputs seldom causes actual circuit failure, but can cause the input stage to soak up several milliamps of supply current unnecessarily or even oscillate.

#5