In TN1176, it says VCCA of unused quad should be powered up. What is the reason to power up unused quad? Can I save power by leave the VCCA floating?
The required power, when the quad is in powered down mode(unused quad is powered down by default internally) but VCCA is poweredup, draws very little current. That is hardly a problem for the users.
There is specific reason we want the VCCA pins to be powered up. Without powering them up, you can potentially draw more current from the other supplies.