The Low Voltage RoboClock (CY7B991V) and RoboClock (CY7B9911V) are completely 3.3V-compatible. The original RoboClock CY7B991/2 (along with the CY7B9910/20/11) requires a 5V V CC supply. However, it is possible to make the output swing to 3.3V-compatible levels in the TTL RoboClock (CY7B991/10/11). The CMOS-level RoboClocks (CY7B992 and CY7B9920) cannot be made 3.3V-compatible due to their design, which produces rail-to-rail output swings. Two termination networks are shown below, either of which make RoboClock compatible with 3.3V systems. For a more in-depth explanation, an application note, "Using CY7B991 (RoboClock), CY7B9911 (RoboClock ) and CY7B9910 (Robo Jr.) in 3.3V Environments" is available from the Cypress website (http://www.cypress.com).