CY2254A

Features:

• Multiple clock outputs to meet requirements of most Pentium® motherboards
-Four pin-selectable CPU clocks @ 66.66 MHz, 60.0 MHz, and 50.0 MHz for support of Intel Triton™ PCIset based PC
-55.0 MHz pin-selectable CPU clock also available (−2 option only)
-Six PCI clocks at 1/2 CPU Clock frequency
-One I/O clock @ 24 MHz
-One Keyboard Controller clock @ 12 MHz (−1 option) or one Universal Serial Bus clock @ 48 MHz (−2 option)
-Two Ref. clocks @ 14.318 MHz
-Ref. 14.318 MHz Xtal oscillator input
• CPU clock jitter < 200 ps cycle-to-cycle
• Low skew outputs
-< 250 ps between CPU clocks
-< 250 ps between PCI clocks
-< 500 ps between CPU and PCI clocks (−2 option)
-CPU clock leads PCI clock by +1 ns min. to +4 ns max. (−1 option)


Pinout




Specifications

Supply Voltage........................................................−0.5 to +7.0V
Input Voltage................................................. −0.5V to VDD + 0.5
Storage Temperature (Non-Condensing) .... −65°C to +150°C
Junction Temperature............................................... +150°C
Package Power Dissipation.............................................. 1W
Static Discharge Voltage............................................ >2000V


Description

The CY2254A is a Clock Synthesizer/Driver that provides the multiple clocks required for a Pentium-based PC. The CY2254A has low-skew outputs (< 250 ps between the CPU Clocks, < 250 ps between the PCI Clocks). In addition, the CY2254A CPU clock outputs have less than 200 ps cycle-to-cycle jitter. Finally, both the PCI and CPU clock outputs meet the 1 V/ns slew rate requirement of a Pentium processor-based system.
The CY2254A accepts a 14.318 MHz reference signal as its input. The CY2254A has 2 PLLs, one of which generates the CPU and PCI clocks, and the other generates the I/O and Keyboard Controller or USB clocks. The CY2254A runs off either a 3.3V or 5V supply.
The CY2254A is available in two options. The −1 option supports the Intel Triton PCIset and provides a 12 MHz keyboard clock on pin 25. The −2 option provides a 48 MHz USB clock on pin 25 and supports the Cyrix® M1 processor.