SDIO is input/Output in AD3694 Datasheet (Rev.B).
It's LOGIC INPUTS (SDIO) in DIGITAL SPECIFICATIONS.
There seems to be mentioning only the specification of the input.
Therefore would you instruct in the specification LOGIC OUTPUTS SDIO, (VOH/VOL and IOH/IOL)?
The information for the SDIO as an output was not included in the AD9634 data sheet unfortunately. The SDIO driver from the AD9634 is very similar to the SDIO driver on the AD9683. You can substitute the values from the AD9683 for the SDIO as an output for the SDIO output on the AD9634.
The information is located on page 7 of the AD9683 data sheet at the bottom of the table. You can find the AD9683 data sheet here: http://www.analog.com/media/en/technical-documentation/data-sheets/AD9683.pdf