H-Bridge MOSFET blowing up

Hi,

I am using a MOSFET H-Bridge IC (ZXMHC3F381N) driven by a MAX4427 MOSFET driver IC to control a motor.

Actually I've got two pairs of those ICs to control 2 motors using the same signals from a microcontroller and, for some reason, the ZXMHC3F381N blows up after a while. VDD is 12V and the current consumption of each motor at stall is 1.2A.

The first output of the MAX4427 is connected to the gates of the two mosfets (P&N) of one side of the H-Bridge and the second output is connected to the gates of the other side. I fix one of the MAX4427 inputs to 0V while making PWM (10KHz) at different duty cycles to the other. If motors run freely (no load), the circuit works just fine but after changing speeds and applying some resistance to the wheels, it will blow up.

Does anyone see any design flaws? I didn't add extra flyback diodes but I expected the ones of the Hbridge to work for me.

Many thanks and any help is very much appreciated.

I'm not surprised if you blow the H-bridge. If you drive the gates of the P and N FETs on one side with the same signal the risc is that both the P and the N FETs will conduct at the same time. You need to make sure that one switches off before the other switches on. Even if the FETs don't blow you will get a lot of noise and current spikes on the supply line.

u need pig and n2g to work together (motor between pid/nid and psd/n2d)so + vcc will pass from pig thru motor to n2g towards -v other pair off . next other gate will open2pg and nig.
post your sketch and ill help.

skogsjanne said:

I'm not surprised if you blow the H-bridge. If you drive the gates of the P and N FETs on one side with the same signal the risc is that both the P and the N FETs will conduct at the same time. You need to make sure that one switches off before the other switches on. Even if the FETs don't blow you will get a lot of noise and current spikes on the supply line.

Click to expand...

Hi! Thanks for the speedy response.

Well, I was more thinking of spikes due to current flowing back through the internal diodes rather than shoot-through problems.
From the datasheet of the ZXMHC3F381N:

N channel: Ton=2.5ns Trise=3.3ns Toff=11.5ns Tfall=6.3ns
P channel: Ton=1.9ns Trise=3.0ns Toff=30.0ns Tfall=21ns

Do you think that those differences in on/off times are likely to provoke a shoot-through problem? Please, notice that I'm using a MOSFET driver (MAX4427) in order to charge/discharge gates capacities as fast as possible.

Regards!

---------- Post added at 17:24 ---------- Previous post was at 17:07 ----------

Hi guys, thanks for your help.

This is the sketch:

**broken link removed**

Many thanks.

Don't know but notice that Ton is much shorter than Toff in both cases. And how about threasholds? Even if they don't blow I think you get a lot of noise. Connect a resistor in series with the supply and use an oscilloscope to look at the current through the drivers and motors (voltage across the resistor).