MOSFET Driver cannot drive a MOSFET? or something wrong?

IXDD414 bypassed enough?

I've never had a problem with the IXDD414..

D from BC British Columbia Canada

My guess is circuit layout or your 1ohm resistor is a wirewound type with significant inductance.

Acording to the IXDD414 datasheet it has a risetime of under

If you have wired this up with six inch long hookup wires then you are going to see ringing.

Bob

Where's your gate resistor? You need one.

(Methinks your FET screams.)

Cheers, James Arthur

what rate are you switching at?

what is the gate capacitance of your FET?

can the driver drive that capacitance at that speed?

Mark

A gate resistor is not always needed, but it seems more likely there is not enough bypass capacitance on the driver circuit. When the driver tries to turn on, it needs to get its current from a voltage source that can handle a high speed pulse. The driver should be bypassed with a low ESR capacitor at least 10x the MOSFET gate capacitance. Also, the gate drive and return tracks should be very short.

The source resistor shown in the schematic should be of low inductance, and careful consideration must be given to the ground path for the high current output. It is not even clear why the source resistor is present, unless it is used for desaturation detection or current mode PWM.

Please provide the entire circuit, including details on what sort of power supply is being used, and a PCB layout or sketch of wiring if it is on a protoboard.

There is good information on high speed circuit design in a Linear Technology app note AN47. It is more about amplifiers, but applies to this as well. And AN25, "Switching regulators for poets". Also look at International Rectifier app note AN-944 on gate charge and drivers for MOSFETs.

Paul

now it's an open loop circuits. the 0.015 is for further close loop circuits use. even I remove 0.015 ohm res the problem is still there. I did it on bread board. I think it is caused by the inductance of load, power supply wires. I don't know how to solve it. I added some big capacitors between vcc and ground, I use separate power supply for that mosfet, it didn't improve too much.

You will get more help if you don't top post like this.

Paul

That's a massive FET.

To turn that beast on super quickly you'll need super layout, tight decoupling, intelligent current paths, short traces, and so forth.

By temporarily using a 10 ohm gate resistor, much will be revealed.

Cheers, James Arthur

(I just saw this post, after posting my other reply...)

You can't do that. It won't work. You need a groundplane. And a smaller FET with a larger gate resistor wouldn't hurt.

Yes.

Build the thing on a solid piece of copper clad. Dead-bug style is good. These problems will vanish.

Cheers, James Arthur

Just a 0.1 uF or so bypass capacitor directly across the driver power terminals should help a lot (like you said, decoupling). Also the connection to the gate and back to the ground pin should be reasonably short. I have a circuit that uses a Fairchild HUF75645 which is almost as beastly as the IRL3803, and I have driven it up to at least 300 kHz with an inductive load without problems, using a TI 9 amp driver. UCC27321. And my first prototype on a perfboard was OK at 100 kHz.

The IRL2803 has 5000 pF gate capacitance, but it has 230 nSec rise time, so a super fast gate driver is not really necessary. A 9 amp driver can provide about 1.8 V/nSec, and realistically about 20 nSec to full on, but the device itself will take ten times that to conduct fully.

There is an app note on the UCC35705 that is used to provide the PWM signal:

This is a 4 MHz part, which may be overkill for the application (or at least the MOSFET). More information is really needed, such as supply voltage and drive frequency.

Paul

That's with just 4.5 volts of gate drive (Fig 10a. in the datasheet) through a 1.3 ohm gate resistor, but 12v and a hot driver could do the job much faster.

You can do a lot on a smart perfboard. The OP's "breadboard" though clearly isn't cutting it, so recommending a groundplane makes up for a lot.

It all comes down to what the OP is doing, which he hasn't told us.

If he's trying to get 15nS pulses from a laser diode with this setup...

Grins, James Arthur