Cyclone 5V Tolerance

[Gary Pace]

I have a couple of questions about this :

1. What is the current limit of the PCI calmp diode when this option is
turned on for an input pin - i.e. what is the correct resistor value.

2. What happens during power up and configuration ? Is the PCI diode in
circuit at this time ?

Thanks

 

[Nial Stewart]

2. What happens during power up and configuration ? Is the PCI diode in
circuit at this time ?

From memory the data sheet discusses limiting the input current using
a resistor. It then says that during configuration the PCI clamp
diode is not in circuit so you need to make sure there are
no 5V signals applied before the end of cunfiguration!

Pretty limiting, I always use IDT quickswitches to protect the
FPGA pins from 5V inputs. They're simple, work well and
cheap as chips (french fries).


Nial

------------------------------------------------
Nial Stewart Developments Ltd
FPGA and High Speed Digital Design
Cyclone Based 'Easy PCI' proto board
www.nialstewartdevelopments.co.uk