5.2.3. Guideline: Observe Device Absolute Maximum Rating for 3.3 V Interfacing
To ensure device reliability and proper operation when you use the device for 3.3 V I/O interfacing, do not violate the absolute maximum ratings of the device. For more information about absolute maximum rating and maximum allowed overshoot during transitions, refer to the device datasheet.
If you use the Stratix® V device as a transmitter, use slow slew rate and series termination to limit the overshoot and undershoot at the I/O pins. Transmission line effects that cause large voltage deviations at the receiver are associated with an impedance mismatch between the driver and the transmission lines. By matching the impedance of the driver to the characteristic impedance of the transmission line, you can significantly reduce overshoot voltage. You can use a series termination resistor placed physically close to the driver to match the total driver impedance to the transmission line impedance.
If you use the Stratix® V device as a receiver, use an off-chip clamping diode to limit the overshoot and undershoot voltage at the I/O pins.
The 3.3 V I/O standard is supported using the bank supply voltage (VCCIO) at 3.0 V and a VCCPD voltage of 3.0 V. In this method, the clamping diode can sufficiently clamp overshoot voltage to within the DC and AC input voltage specifications. The clamped voltage is expressed as the sum of the VCCIO and the diode forward voltage.