CY2280 Datasheet | Cypress

Features - Mixed 2.5V and 3.3V operation - Clock solution for Pentium® II, and other similar processor-based motherboards - Four 2.5V CPU clocks up to 100 MHz - Eight 3.3V sync. PCI clocks, one free-running - Two 3.3V 48-MHz USB clocks - Three 3.3V Ref. clocks at 14.318 MHz - Two 2.5V APIC clocks at 14.318 MHz or PCI/2 - EMI control - Spread spectrum clocking - Factory-EPROM programmable spread spectrum margin - Factory-EPROM programmable output drive and slew rate - Factory-EPROM programmable CPU clock frequencies for custom configurations - Available in space-saving 48-pin SSOP package Functional Description The CY2280 is a Spread Spectrum clock synthesizer/driver for a Pentium II, or other similar processor-based PC requiring 100-MHz support. All of the required system clocks are provided in a space-saving 48-pin SSOP package. The CY2280 can be used with the CY231x for a total solution for systems with SDRAM. The CY2280 provides the option of spread spectrum clocking on the CPU and PCI clocks for reduced EMI. A downspread percentage is introduced when the SEL_SS input is asserted. The device can be run without spread spectrum when the SEL_SS input is deasserted. The percentage of spreading is EPROM-programmable to optimize EMI-reduction. The CY2280 has 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. CY2280 Selector Guide CY2280 Configuration Options Clock Outputs CPU (66.6, 100 MHz) PCI (CPU/2, CPU/3) USB (48 MHz) APIC (14.318 MHz) APIC (PCI/2) Reference (14.318 MHz) CPU-PCI delay CPU-APIC delay Spread Spectrum (Downspread) - 1 4 8 2 2 - 3 1.5- 4.0 ns -...