Part Number: DRV8323R
We have a design using the DRV8323 that has been working great but every once in a while the DRV8323 fails with all the fet gate drives shorted. The Mosfets are fine! The etches to pins 7 (VDRAIN), 8(GHA) and 9 (SHA) get blown off the PCB making the board un-repairable. The PCB layout was taken from the App notes and Data sheet. The pcb copper is 2oz. The board temperature by the DRV8323 is 50C. We use it in PWM x 1 mode, supplying a 15KHz signal. The supply voltage is 48Volts and has a large snubber to keep the supply to less than 52 volts (measured) during a back EMF event. The motor is rated for 500 watts. The internal switching power supply continues to operate properly! Please advise
In reply to David Cassidy:
Motor Drive Solutions
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I used anther scope and probes to verify the waveforms I was measuring. Both scopes have similar wave forms but the second scope the spike voltage was 2-3 volts higher. The BW limit was on in the first scope.
I don't see how to just change the low side mosfet turn on time (I'm not using the spi bus) with out adding a gate resistor/diode. I tried lowering the gate drive current from an iDrive Resistor value of 18K to infinite. (570/1140ma down to 120/240ma) The spike drops 4-5 volts so it has gone from low 60s to high 50s volts. The board runs a few degrees warmer. What is a safe limit? Should I try a gate resistor and diode?
I ordered some schottky didoes. I also looked for a negative spike below ground and see a -5V spike in the 20ns wide range. Should I also put diodes to ground?
I added in the schottky diodes as you suggested. The spike dropped again but was not eliminated. I lowered the gate drive current again, which seems to have the biggest impact. I have been running the system now for days starting and stopping the motor quickly and changing speeds with no failures. I removed the schottky diodes and have again have run the motor for days monitoring for spikes and have not seen any spikes greater than 2 volts over the power supply. Comments?
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