CY2278A

The CY2278A is a Clock Synthesizer/Driver chip for Pentium, or Pentium II portable PCs designed with the 82430TX or similar core-logic chipsets. There are four options available as shown in the selector guide.

The CY2278A outputs seven CPU clocks, three of which run at 3.3V and four run at either 2.5V or 3.3V, depending on the voltage applied on pin 42. There are ten PCI clocks, running at one half the CPU clock frequency. Free-running PCI and CPU clocks are available as options shown in the selector guide. Additionally, the part outputs two 3.3V USB/IR clocks at 48 MHz, one Keyboard clock at 8 MHz, one 2.5V IOAPIC clock at 14.318 MHz, and two 3.3V reference clocks at 14.318 MHz.

The CY2278A family contains several features for output flexibility and power control. The CPU, PCI, USB and IR clock frequencies are all factory EPROM-programmable. Three hardware select inputs support eight CPU clock frequencies from 20 75 MHz. Additionally, each of the CPU, PCI, and USB/IR clock sets can be turned on or off with a dedicated enable input pin for power management.

The CY2278A outputs are designed for low EMI emissions.

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