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Which driver to choose?

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darkfeffy

New Member
Hello,
I need someone to refer me an n-channel mosfet gate driver they have "successfully" used with a PIC18f series microcontroller and if possible a circuit diagram. I have been trying unsuccessfully the past few weeks to make my PIC 18f2520 work with the IR21844 gate driver in my H-bridge inverter configuration (See attachment for circuit diagram).
When out of circuit, the PIC works fine. When connected to the gate drivers, the PIC works till when the Mosfets are supplied. Then the PIC pins (CCP1 and 2) will either go all high or low. The PIC would just stop working when in-circuit. A resistance b2een the PIC and gate driver (33ohm, 1kohm) doesn't solve the problem, nor a voltage follower I have tried. A 50kHz TTL function generator I have was able to drive the IR21844 well and directly (very small current drawn \approx 9mA).
Don't exactly know what is wrong. But after several tests/experiments I am tempted to conclude the gate driver is either not compatible with my pic or has a few issues. I want to use the gate driver in a boost and buck as well, but with this problem already, I think I would need a "better" driver. Thanks alot.
Ed
 

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BrownOut

Banned
I honestly don't think your drivers are the problem. I think either your circuit is malfunctioning, or your power supply is malfunctioning or your motor has a short or your motor is just drawing too much power. Next time, measure your power supply rails when you power your circuit up. If you see a big drop in voltage, try again without the motor. Also check exactly which of the FETs are actually turned on.
 

darkfeffy

New Member
Hello BrownOut,
I have not connected any load yet...The PIC is just unable to "drive" the driver. I repeat that I have tried a function generator and the gate driver responds well. Think it might be something in the output of the PIC that's not compatible with the driver (whose datasheet says it is CMOS, LSTTL compatible).
I think I should try using an opto-coupler and separating their grounds
Thanks for any updates
Edwin
 
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