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Observer rickwebb38
Observer
582 Views
Registered: ‎01-18-2018

Kintex-7 XC7K160T-1FFG676I HP banks 32, 33 & 34 powered from 3V3 problem?

Hi,

We have a board design that has banks 32-34 unused, so we added loop-back connections between all unused pins so that they can be checked for adjacent shorts during JTAG boundary scan.

The power pins for these HP banks currently connect to 3V3 rather than 1V8, so my question is: what long term effect will this have on the device?

In operation we have seen no damage and the device functions correctly, but UG471, p.18, says that if the VCCO for the HP I/O banks is >= 2.5V, the device automatically enters an overvoltage protection mode.

Does this mean that this 'protection mode' only effects the HP banks, and will the device suffer in any way, if operated with the HP banks powered from 3V3?

 

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4 Replies
Xilinx Employee
Xilinx Employee
574 Views
Registered: ‎03-07-2018

Re: Kintex-7 XC7K160T-1FFG676I HP banks 32, 33 & 34 powered from 3V3 problem?

Hi @rickwebb38

 

As per DS182 (v2.16.1) you are exceeding Absolute Maximum Ratings of VCCO of HP bank; which can cause damage to your device. Even if device is working currently;  Driving FPGA power rails of outside of the recommended operating range can cause timing failure.

 

absolute max Kintex7.png

Regards,

Bhushan

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Regards,
Bhushan

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Observer rickwebb38
Observer
566 Views
Registered: ‎01-18-2018

Re: Kintex-7 XC7K160T-1FFG676I HP banks 32, 33 & 34 powered from 3V3 problem?

Hi Brushan,

 

I understand that we are violating the 'Absolute Maximum Voltage' for the HP banks, but UG471, p.18 says the following:

 

"In HP I/O banks, if the I/O standard voltage requirement is <= 1.8V, but a VCCO >= 2.5V is applied, the device automatically enters an overvoltage protection mode. Reconfiguring the device with the correct VCCO level restores normal operation".

 

From this, can you get an answer to the question of: Whilst in overvoltage protection mode, does this effect operation within other banks and what is the long term effect of operating in this mode?

 

Regards,

rickwebb38

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Observer rickwebb38
Observer
556 Views
Registered: ‎01-18-2018

Re: Kintex-7 XC7K160T-1FFG676I HP banks 32, 33 & 34 powered from 3V3 problem?

Hi Brushan,

As a follow-up question, can you let me know whether it is acceptable to isolate the HP power pins on the FPGA, as we don't use any of the HP pins in our design?

Regards,

rickwebb38

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Moderator
Moderator
499 Views
Registered: ‎09-18-2014

Re: Kintex-7 XC7K160T-1FFG676I HP banks 32, 33 & 34 powered from 3V3 problem?

Rickwebb38,

 

Whilst in overvoltage protection mode, does this effect operation within other banks and what is the long term effect of operating in this mode?

-You need to understand that each IO banks have their own VCCO plane. So over supplying one IO bank VCCO does not mean you will also oversupply another IO bank. Long term effect of operating in this mode is damage... either latent damage or immediate damage depending on how grossly above the absolute max the violation is. See below diagram from Industry council white paper on EOS/ESD. 

 

EOS MAX rating.JPG

 

If you are not using the HP banks then connected them to a 1.8V supply plane or lower, even GND will do. If you already have external ESD protection circuitry then they can be left unconnected but I suggest against it unless additional PCB or reason is substantial to the design. 

 

unconnected VCO.JPG

 

Regards,

Tezz

 

Regards,

Tezz

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