Using Cyclone Devices in Multiple-Voltage Systems

To meet the demand for higher system speed in data communications,
semiconductor vendors use increasingly advanced processing
technologies requiring lower operating voltages. As a result, printed
circuit boards (PCBs) often incorporate devices conforming to one of
several voltage level I/O standards, such as 3.3-V, 2.5-V, 1.8-V and 1.5-V.
A mixture of components with various voltage level I/O standards on a
single PCB is inevitable.
In order to accommodate this mixture of devices on a single PCB, a device
that can act as a bridge or interface between these devices is needed. The
Cyclone? device family’s MultiVolt? I/O operation capability meets the
increasing demand for compatibility with devices of different voltages.
MultiVolt I/O operation separates the power supply voltage from the
output voltage, enabling Cyclone devices to interoperate with other
devices using different voltage levels on the same PCB.
In addition to MultiVolt I/O operation, this chapter discusses several
other features that allow you to use Cyclone devices in multiple-voltage
systems without damaging the device or the system, including:
■ Hot-Socketing—add and remove Cyclone devices to and from a
powered-up system without affecting the device or system operation
■ Power-Up Sequence flexibility—Cyclone devices can accommodate
any possible power-up sequence
■ Power-On Reset—Cyclone devices maintain a reset state until
voltage is within operating range