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a question about FPGA

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bashir2000

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Hello dear all,

I have run into a problem regarding the FPGA. The FPGA output signal amplitude is 3.3, and to drive my switches, I need to increase the voltage up to 15 V. I am using TC4427(dual power mosfet driver)as a buffer after FPGA , and would like to check the possibility of my gate driver, but whenever I wanna check it, the FPGA pin is destroyed. I personally believe a resistance is required in series with the IC. Could you please give me a hand with this problem if you do not mind?
I highly appreciate your prompt answer.

Best Regards,
Bashir
 

enren

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If you check for some transistor buffers schematics on the web, you'll find out you got to convert the low FPGA output impedance by a high input impedance for the driver.
 

bashir2000

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If you check for some transistor buffers schematics on the web, you'll find out you got to convert the low FPGA output impedance by a high input impedance for the driver.

Thanks for your reply, but would you please give me a clearer picture on your answer?
 

rhaynes

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The only problem I can see with that part is that it requires a 2.4V minimum for a high (unless you have a V temp part). The 3.3V FPGA out should be over that but isn't guaranteed. But since the input current is less than 1uA I'm sure the FPGA pin is reaching 3.3V.

But that doesn't explain the FPGA pin blowing up. I would guess that either you have a wiring error or a bad TC4427 and it is coupling the 15V to the control pin FPGA.

If your FPGA's I/O pin is 5V tolerant then I would try running the 15V at 5V until you get the problem solved. That will prevent the FPGA from getting blown up. If not then if possible disconnect the control pin from the FPGA and pull it up to 3.3V with a 1K Ohm resistor and see if the driver works and that the voltage at the input pin is only 3.3V. Also try pulling it down while measuring the voltage on the pin to make sure it's ground. This checks to see if the pin is suppling any current which could raise the voltage on the FPGA pin too high.

Ray
 

bashir2000

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The only problem I can see with that part is that it requires a 2.4V minimum for a high (unless you have a V temp part). The 3.3V FPGA out should be over that but isn't guaranteed. But since the input current is less than 1uA I'm sure the FPGA pin is reaching 3.3V.

But that doesn't explain the FPGA pin blowing up. I would guess that either you have a wiring error or a bad TC4427 and it is coupling the 15V to the control pin FPGA.

If your FPGA's I/O pin is 5V tolerant then I would try running the 15V at 5V until you get the problem solved. That will prevent the FPGA from getting blown up. If not then if possible disconnect the control pin from the FPGA and pull it up to 3.3V with a 1K Ohm resistor and see if the driver works and that the voltage at the input pin is only 3.3V. Also try pulling it down while measuring the voltage on the pin to make sure it's ground. This checks to see if the pin is suppling any current which could raise the voltage on the FPGA pin too high.

Ray

Many thanks for your answer. I put a 1KΩ resistor in series with the IC . Now, the FPGA pin is not destroyed, and the output signal amplitude of the IC is equal to power supply, but the problem is that we do not see any pulse. The series resistor keeps the FPGA pins safe, but no pulses are appeared on the oscilloscope. Would you please let us benefit from your suggestion? BTW, the frequency we are working with is 20 Khz.
Thanks again for your help buddy
 

rhaynes

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With 12pF of input capacitance on the driver pin the 1K resistor has little affect on the operation at 20KHz and will provide some protection of the FPGA pin but more importantly it provides a troubleshooting point. Check both sides of the resistor, you should see the 20KHz signal on both sides. If not then the TC4427 is wired wrong or blown. Based on the FPGA pin getting blown I'm guessing you are going to see something other than the correct signal on the driver side of the resistor.

Ray
 

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