CoolRunner-II CPLD i/p voltage tolerence?

[sachingorkhe]

how coolrunner-ii works

Hi All,

I am using XC2C64A coolrunner-II CPLD for my project. Its a basically 1.8V compatible CPLD. But I need 2-3 I/O's for 3.3V compatible. I don't want to use a level translator form 3.3V to 1.8V.

In the datasheet, it mentioned that "The CoolRunner-II input buffer can tolerate up to 3.9V without physical damage."

So can I directly connect my 3.3V signals to this CPLD? :?:

Reply ASAP expected. Please find what the attached datasheet mentioned?

Thanks in advance.

Sachin

 

[sadashiv_sm]

Hi sachingorkhe...

For this CPLD XC2C64A There are two supply ...called VCCIO1 And VCCIO2....
you can connect this to 3.3V....please see your datasheet carefully.....
there are two banks .....Bank1 and Bank2 for this CPLD.......
you have to connect VCCIO1 and VCCIO2 to thses banks.....

see the attached picture for VCCIO details....

 

[sachingorkhe]

Hi Sadashiv,

Thanks for your reply. I know there are 2 banks available for different supply I/Os.
What my question is I want 3 pins only for 3.3V tolarable. I am using rest of all pins on 1.8V interface.

Can I connect these 3 pins of 3.3V to my 1.8V I/O pins? As xilinx have mentioned it clearly.

Corect me if misunderstood.

Thanks,
Sachin

 

[sachingorkhe]

Thanks guys for ur coopration. I used a resistor voltage divider to reduce the voltage level from 3.3V to 1.8V.

Thanks,
Sachin

 

[echo47]

Hi sachingorkhe, As you mentioned in your original question, the data sheet says the input buffers withstand up to 3.9V even when VCCIO is only 1.8V. That sounds like you don't need a resistor divider for 3.3V, however I haven't actually tried it. The input threshold voltage may be a little low for your 3.3V signal, but the reduced noise margin may not matter in your project. If you are still worried about all this, you can ask Xilinx by submitting a WebCase via their web site. They usually reply within one or two business days.

 

[sachingorkhe]

Hi echo47,
There is no issue of reduced noise margin. I have implemented it on the board and it works fine for me.
Thanks for your reply. I appreciate.

Sachin