I should also point out that the USBi board holds SCA/SCL "sort of" high when the host PCB (with SigmaDSP) power is shut down, to about 1.3V (in my circuit), and this creates about 1V to IOVDD due to other loading on that power net. Per the spec (Table 8), this is right on the edge of the maximum allowed rating. This might present a problem for some people whose circuit may pull IOVDD lower than this; a diode might be a good recommendation.
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