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anjilun
Visitor
Visitor
553 Views
Registered: ‎06-26-2021

XC6VLX195T-1FFG1156C

A1 is GND,A3 is MGTTXP,Why are they connect? Is there a quality problem with the parts?

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4 Replies
drjohnsmith
Teacher
Teacher
521 Views
Registered: ‎07-09-2009

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.

 

 

<== If this was helpful, please feel free to give Kudos, and close if it answers your question ==>
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anjilun
Visitor
Visitor
482 Views
Registered: ‎06-26-2021

Hello, teacher

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!

WeChat 圖片_20210627092339.png

 

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bruce_karaffa
Scholar
Scholar
428 Views
Registered: ‎06-21-2017

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?

joancab
Teacher
Teacher
379 Views
Registered: ‎05-11-2015

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?

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