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circuit design current limiting precautions

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Full Member level 6
Jan 17, 2008
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My PCB 3V rail is bad. Discovered that its caused by the 3 V regulator. The 3V rail provides power to the FPGA. I am looking to replace the regulator by ordering new parts through but in the mean time while I wait for those regulators to arrive is there any objection to providing 3 Volts to my FPGA from a power supply?

For instance I was thinking what if the Voltage supply pin for the FPGA is somehow damaged via the 3V regulator and the pin is shorted some way? If I power the FPGA via power supply and the pin is shorted i could damage other parts of the boards.

Will a continuity test on the fpga power pin be enough evidence to determine if the pin is shorted or not? If its not shorted can I go ahead and use a power supply to provide power to the FPGA?

Are there current limiting power supplies out there that can help with preventing some of the concerns that I have? Or am I being to overly cautious and concerned?

If the "bad" regulator went short circuit input to output, your FPGA could be toast. Any decent laboratory PSU would have inbuilt and adjustable current regulation. If your chip is feeding some thing off-board then a short circuit at this point, could cause the chip to expire. In general there is no provision for current limitting with on-board regulators. It might be a good idea to feed your new regulator with a resistor, so if there is a short circuit on it, it will not be damaged again. If you know what the typical power consumption of the board is, put ten ohm resistor in series and them measure the voltage drop across it, and the + 3V line. This way you can see if every thing is in order before removing the ten ohms.

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