CY23FS04

The CY23FS04 is a FailSafe^TM zero delay buffer with two reference clock inputs and four phase-aligned outputs. The device provides an optimum solution for applications where continuous operation is required in the event of a primary clock failure.

The continuous, glitch-free operation is achieved by using a DCXO, which serves as a redundant clock source in the event of a reference clock failure by maintaining the last frequency and phase information of the reference clock.

The unique feature of the CY23FS04 is that the DCXO is in fact the primary clocking source, which is synchronized (phase-aligned) to the external reference clock. When this external clock is restored, the DCXO automatically resynchronizes to the external clock.

The frequency of the crystal, which will be connected to the DCXO must be chosen to be an integer factor of the frequency of the reference clock. This factor is set by two select lines: S[2:1], please see Table 1. Output power supply, VDD can be connected to either 2.5V or 3.3V. VDDC is the power supply pin for internal circuits and must be connected to 3.3V.