06-26-2021 11:06 AM - edited 06-26-2021 11:10 AM
in circuit or out of circuit ?
How did you measure this ?
Did you purchase from an authorised distributer ?
If its on a board, might be a quality problem
with your board or soldering quality ,
Out of circuit
be careful not to forward bias the inherent diodes in the chip
From a none authorised distributor
then it could be anything, I've seen chips with no silicon in them being flogged on far eastern sites.
06-26-2021 06:40 PM
I am a new student, I use a multimeter to measure A1 pin and A3 pin, forward resistance value is 0.2 Ohm, Reverse resistance value is 0.2 Ohm. ( Out of circuit, not on a board )
A1 pin define GND and A3 pin define MGTTXP in the datasheet, Why are these two pins connect in internal? below picture
thank you very much!
06-27-2021 03:22 AM
These pins are probably not shorted. The multimeter is probably applying a high enough voltage to the pins to activate the protection diodes. FPGA inputs typically have protecting diodes to GND and the voltage rail for that bank. The multimeter must apply a voltage and measure the resultant current to determine DC resistance. If the voltage is high enough to activate the diodes, current will flow with very little resistance. If the current is too high or applied for too long, this can damage the input circuit. Why are you trying to measure anything on a chip that is not in-circuit?
06-27-2021 09:57 AM
Never do that (flipping an FPGA and start checking continuity with a DMM). Not only you are applying voltages between pins but also there is the risk of ESD from your hands and you have taken the chip from its package now it will need to be baked before soldering. Do you also check the diameter of coins when given change at a shop?