I'm going to use a L6491 High voltage high and low-side 4 A gate driver to drive an half bridge made from two IPW65R019C7. I'm going to use a +15V to supply the L6491 MOSFET Driver.

How can I have an idea about the current drawn by the L6491 from the +15 power supply?

I don't know exacly which is the parameter on the datasheet which gives me this infomation.

Following the L6491 datasheet:
https://www.st.com/resource/en/datasheet/l6491.pdf

Thank You.

 

Your answer can be found partly in your first sentence, 4A, plus the currents listed on page #11 table 8. But would also have to allow a little more since you don't give more information about what else is using the 15V supply.

 

You have to calculate the current from the total gate charge of the FETs at the voltage used. You will find curves in the datasheet. This gives you the charge in coulombs per cycle (ampere-seconds per cycle; typically tens to low hundreds of nanocoulombs), so you must multiply that by frequency (cycles per second) to get the current. At moderate frequency (e.g. 100 kHz) it typically is in the range of a few tens of millamperes. Since there are two FETs, each must be considered. The current for the driver itself will be spec'd in the datasheet.