Do the digital inputs on the DIO ports of the sbRIO 9642 require pull-down resistors?

[dave_burbridge]

We are using an sbRIO-9642 to control several relays and read positive open/close states back. There is a recommendation at http://digital.ni.com/public.nsf/allkb/12A56A7C6526D885862576B1004B5D19 to add 10K pull-down resistors to the DIO outputs to prevent spurious output voltages during startup.

Are pull-down resistors also required on the DIO inputs for any reason? We are designing the circuitry right now and want to ensure we allow enough space, but don't want to provide space if it won't be needed!

Thanks,

Dave

[Dominic.Walker]

Hey Dave,

I can't see any reason why the pulldown resistors would be needed on the inputs.  However, you may want to put them in anyway if there is a chance the application may change and you end up using them as output lines. 

Kind regards,

[dave_burbridge]

Thanks Dominic.

Another related question - when using the DIO ports in input mode, can they take +5V or just +3.3V? If +5V, for how long is a reasonable time? seconds? minutes? hours?

[Dominic.Walker]

Hey,

If you look at page 36 of the specifications: http://www.ni.com/pdf/manuals/375052c.pdf it mentions the max voltage of the 3.3V DIO lines is 5.25V.  So constant 5V should be fine if you're confident it wont spike. 

Cheers,