UCC21542: Mosfet driver continously get burnt

Hi Abayomi,

Thank you for your interest in our device.

Some clarifying questions to better assess the situation:

• Which components were burned/damaged?
• Where is the 1A fuse located?
• Would you be able to share the layout?

Looking forward to hearing back.

Regards,

Hiroki

Thank you Hiroki,

Enclosed is the copy of hte layout

diagram_2.rar

The mosfet driver, the mosfet and the1A fuse are affected.  The mosfet becomes shorted, and mosfet driver bad.

The circuit diagram is tested with a small load connected to it and at the moment for open loop test.

Thanks

Babatola Abayomi

Hi Babatola,

Thank you for the follow-up!

Could it be that the MOSFETs are getting too hot? Does the setup have a heat sink with thermal paste? 

Would you happen to have waveforms to help narrow down the source of the issue? If the issue lies around the driving circuitry, waveforms of the input, output, and supply of the gate driver would help figure out what is causing the short. I am mostly only able to comment on the gate driver circuitry, but this could be related to the control or the converter component selection as well. Hope to resolve this as soon as possible!

Regards,

Hiroki

Hi Honda,

Thank you for your reply.

It seems from your reply tha the circuit diagram is fine.  Is this correct?

The components get burnt instantly once the PWM of the C2000 drives the mosfet through the mosfet driver.

I use heat sink but without thermal past and  I have a dummy load of 100w, 4.7k ohm dummy load.

I have observed the waveform of the circuitry but did not seem to find anything.  The circuit diagram have been reveiwed over and over again.

I would await your further input

Thanks.

Hi Babatola,

The design looks well thought out and carefully made.

I am wondering what type of damage is on the gate driver. Could you measure the following impedances on the device pins?:

• VDDA - OUTA (pin 16-15)
• VDDA - VSSA (pin 16-14)
• OUTA - VSSA (pin 15-14)
• VDDB - OUTB (pin 11-10)
• VDDB - VSSB (pin 11-9)
• OUTB - VSSB (pin 10-9)

Also if possible, a picture of the set up or board layout would be very helpful. 

Thank you for your patience and follow ups!

Looking forward to hearing back,

Hiroki

Hi,

Have you been able to check again?

Thanks

Hi Babatola,

Apologies for the late response! The thread got closed due to the green resolved button.

On a breadboard, there is definitely much more parasitics coming into play here. Some of the most important areas to keep a short as possible loop would be the gate loop, VDD supply decoupling loop, and the switch node loop. These loops are highly sensitive to extraneous parasitic inductances that can introduce noise that could potentially damage the driver. 

One recommendation would be to try to have as short as possible leads on your setup, especially in the important nodes, to see if these issues resolve. 

Abayomi Babatola said:

From the data sheet it was stated that the Rs could be between 10 kohms to 20 kohms.  I observed that 14 kohms does not switch on the mosfet but 12 kohms leads to the mosfet and the fuse been burnt.  The mosfet driver did not get burnt.  Does this have any interpretation.

This is referring to the gate to source resistor for the power FET correct? The resistance value of this resistor is dependent on the threshold voltage of the FET as well as the ratio between the gate to drain capacitance and the gate to source capacitance. This range of resistor values takes into consideration the possible FET threshold and intrinsic capacitance ratios, so the full range of resistance values is not expected to work with one specific FET. 

Thank you for your patience and please feel free to ask any questions!

Regards,

Hiroki