What will it be if one GND pin of my FPGA is disconnected???

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zcq

Joined: 14 Jul 2001
Posts: 112
Helped: 1

27 Feb 2003 15:10 What will it be if one GND pin of my FPGA is disconnected???

The FPGA is xilinx's XCV2000.

Thx!

ZmGor

Joined: 21 Feb 2002
Posts: 37

27 Feb 2003 15:36 Re: What will it be if one GND pin of my FPGA is disconnecte

zcq wrote:

The FPGA is xilinx's XCV2000.

On frequencies less than 50 MHz anything terrible will not take place.
If it GND I/O pin, can the level of a signal will decrease during front.

igorz

Joined: 30 Mar 2002
Posts: 16

27 Feb 2003 23:19

GND pins are connected inside FPGA with mutual impedance of no more then several Ohms and with some parasitic inductance.

When one or more GND pins are disconnected, it will slightly increase FPGA's GND plane resistance (which is of a little importance in most cases) and plane inductance (which can increase ground bounce for fast output drivers in some situations).

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mariaR

Joined: 28 Feb 2003
Posts: 200
Helped: 1

02 Mar 2003 6:28

It's interesting question! the GND pin was there for a reason. The fist thing I know is the chip will have degrade performance. In CMOS we need path to VCC for the pull up and GND for pull down. If one of the ground pin was disconnect, the pull down resistance will be higher and it wook make a lower transition on falling edge. In general, the propagiation delay will be longer.. It may not affect if your design is working in a very low frequency than the chip's spec, but in general, it will give you a failure

mami_hacky

Joined: 28 Mar 2002
Posts: 724
Helped: 4
Location: Some where

02 Mar 2003 6:52

Once I saw a schematic for one of Xilinx FPGAs, GND pins were connected to each other with a ring inside FPGA.
Any how In Virtex-II data sheet there is a limitation for maximum simultenous output switching. This value is defined due to number of VCC , GND pins, e.g. for each VCC and GND pin you can have only 12 simultaneous output switching pins (of course for a special signaling standard and drive strength) . may be, this shows that the correct connection of each GND pin to real ground is some thing important.

delay

Joined: 11 Jun 2004
Posts: 219
Helped: 3
Location: Van Allen Belt

25 Jun 2004 8:08 Re: What will it be if one GND pin of my FPGA is disconnecte

The FPGA will probably work because there is ample ground on other pins.
Internally similar ground pins are connected anyway. However, system won't be robust enough and susceptible to noise.

delay (delayed by technology)

jay_ec_engg

Joined: 19 Jun 2004
Posts: 157
Helped: 1
Location: India

29 Jun 2004 9:12 Re: What will it be if one GND pin of my FPGA is disconnecte

Your chip will work anyway...
not 100% but....some I/O will not work properly... or if it will work then it will be noisy......
there will be many GND and VCC pins .. these gnd and VCC will be the core voltage of the chip. and some are for I/O voltage....
So it that GND will be related to I/O bank then those I/O wont work... otherwise chip will work nicely..

Jay