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MSP430F147 best practice for unused voltage reference inputs

I'm wondering if I should tie VeREF+ and/or VREF-/VeREF- to ground.  Currently I have VREF-/VeREF- tied to the ground of my Vref decoupling cap, and VeREF+ floating.

 I know it is good practice to tie unused digital inputs to ground (or set them to outputs in software), to prevent them from "flapping in the wind".  Does this hold true for the reference input pins as well?  Are there any analog buffers that could cause some on chip noise?

  • IF VeREF is a dedicated pin, there is no digital input circuitry. The main problem with digital inputs is that they cause some internal current when the input voltage is near the high/low transition point. If there is no analog input on this pin, this won't happen.

    However, a floating input is an antenna, and worst case you may catch some charge that causes a destructive input voltage. (I'm not sure whether this pin has clamp diodes.)

    And even if there is no danger of damage, any signal on the pin can of course cause some internal crosstalk. The analog switches minimize this by forming a T-siwtch with a GND node between, but no signal at all is better than a heavily attenuated. So yes, I guess connecting VeREF+ to GND is a good idea. At least it won't hurt.

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