CY2275A

The CY2275A is a Clock Synthesizer/Driver for a Pentium and Pentium II-based PCs using an Intel 82440LX or similar core-logic chipset.

The CY2275A outputs four CPU clocks at 2.5V. There are seven PCI clocks, running at one half the CPU clock frequency.

One of the PCI clocks is free-running. Additionally, the part outputs twelve 3.3V SDRAM clocks, two 2.5V IOAPIC clocks at 14.318 MHz, and one 3.3V reference clock at 14.318 MHz.

The part has power-down, CPU stop, and PCI stop pins for power management control. These inputs are multiplexed with SDRAM clock outputs, and are selected when the MODE pin is driven LOW. Additionally, these inputs are synchronized on-chip, enabling glitch-free output transitions. 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.

Finally, when the PWR_DWN pin CY2275A is asserted, the reference oscillator and PLLs are shut down, and all outputs are driven LOW.

TThe CY2275A outputs are designed for low EMI emission.

Controlled rise and fall times, unique output driver circuits and factory-EPROM programmable output drive and slew-rate enable optimal configurations for EMI control.