DRV8251A: Vref pin imput impedance?

Tool/software:

Hi All,

Does anybody have any details of a specification for the input impedance of the Vref pin on the DRV8251A?

Our application requires extremely low shutdown current for all parts of the circuit in some modes of operation. It would be extremely useful to know more about what sort of current this pin is likely to sink or source with with various voltages applied to it and how to treat the pin in order to acheive minimum power dissipation.

This spec seems to be missing from the datasheet (unless it's staring me in the face and I can't see for looking).

Thanks in advance.