CY2285

The CY2285 is a clock synthesizer/driver for Pentium II, or other similar processor-based mobile PCs requiring up to 100-MHz support. The CY2285 outputs two CPU clocks at 2.5V. There are six PCI clocks, running at one-half or one-third the CPU clock frequency of 66.6 MHz and 100 MHz respectively.

One of the PCI clocks is free-running. Additionally, the part outputs two 3.3V reference clocks at 14.318 MHz.

The CY2285 provides incorporates the Intel®-defined spread spectrum features. It provides a 0.6% downspread on the CPU and PCI clocks, which can help reduce EMI in certain high-speed systems.

The CY2285 possesses power-down, CPU stop, and PCI stop pins for power management control. The signals are synchronized on-chip, and ensure glitch-free transitions on the outputs.

When the CPU_STOP input is asserted, the CPU clock outputs are driven LOW. When the PCI_STOP input is asserted, the PCI clock outputs (except the free-running PCI clock) are driven LOW. When the PWR_DWN pin is asserted, the reference oscillator and PLLs are shut down, and all outputs are driven LOW.

The CY2285-2 features an early PCI clock which leads the other PCI clocks by 14 ns. The CY2285-2 also features a DIV4 pin which allows for dynamic shifting of CPU and PCI clocks from the default frequency to the default/4.