# How to calc isolated DC-DC rating for Gate Driver which drives 5 MOSFET in parallel?

I am Kalpesh. I am using FOD8316 gate driver to switch IRFP4668 MOSFETs and the DC-DC used for FOD8316 is MGJ2D121509SC which provides +15VDC/-8.7VDC output vtg with current rating of 80mA/40mA respectively. Now, I want to add parallel MOSFET to increase the continuous current rating of the devices. But I am not confident about using same power supply. Can you please help me out by guiding me to resolve my queries related to paralleling MOSFETs and choosing Gate driver Power Supply.

My issues are as follows:

1.How to calculate the rating of DC-DC required for Gate Driver switching single Mosfet & What must be rating of DC-DC required for Gate Driver switching 5 Mosfets in parallel? (With Peak & Continuous Currents)

2.Will this Schematic work for using 5 Mosfets in parallel?

3. Do I need to make by own DC-DC or purchased one will do the job? If purchased on will work then please tell me what to look for while purchasing & if not then can you please provide me a reference schematic or application note for making one?

4.The peak current while turning ON gate is aroung 7.27amps. So do I req [Ipeak*ΔVgate = 7.27*24 = 174.48W] 180W of DC-DC.

Following is the schematic which I have used & Rg = 3.3Ohm:

Here is what I found from AN-1001 article:

1. The required driver Power : (Which I think should be the rating of Gate driver but can be considered to be the rating of Power supply.)

Pdrv = QgateFinΔVgate= 241nC*16Khz*24 = 0.092544 W

Pdrv of 5 = 0.092544*5 = 0.46272 W

1. Maximum Drive Current : (I am confused about this but I think this should be the peak current rating of Gate driver but can be considered to be the rating of Power supply.)

Iout = ΔVgate/Rgate = 24/3.3 = 7.27Amps

So peak current must be 8Amps.

Parameters which may be req for calc:

Vds= 48V, Ids(on)= 200Amps Continuous, Ids(on)= 600Amps Peak, Qgate = 241nC, PWM freq = 16Khz, Rgate = 3.3Ohm, ΔVgate=24VDC.

• Thats a weird symbol for a mosfet... – BeB00 Apr 30 '18 at 12:16
• I use Altium and I am just a beginner so please bear with my small mistakes. – Kalpesh Mhase Apr 30 '18 at 12:23