On the datasheet for the VNH3SP30 there is a logic high minimum, but no maximum. The majority of my circuitry is running at 24V (using a PLC), so it would be easy for me to send 24V as my high signal. Can i do this without frying the chip or do I need to supply a 5V signal? Will I need to do anything differently (say, supply 24V at V_in) to make this work?
Also, what is the difference between In_A and In_B versus EN_A and EN_B?
You should probably not exceed the input clamp voltage rating on the logic input pins. According to the datasheet, the input clamp voltage is between 6 and 8V, so I do not recommend applying more than 6V for your logic HIGH.
I am not sure what you are getting at by asking the differences between the IN and EN pins, but a description of the function of those pins can be found in the VNH3SP30 datasheet. If you let me know how you want to control those pins, I could tell you whether it sounds appropriate.