Features: •Mixed 2.5V and 3.3V operation
•Complete clock solution to meet requirements of Pen-tium®, Pentium® II, 6x86, or K6 motherboards
-Four CPU clocks at 2.5V or 3.3V
-Up to eight 3.3V SDRAM clocks
-Seven 3.3V synchronous PCI clocks, one free running
-Two 3.3V USB/IO clocks at 48 or 24 MHz, selectable by serial interface
-One 2.5V IOAPIC clock at 14.318 MHz
-Two 3.3V Ref. clocks at 14.318 MHz
•Factory-EPROM programmable CPU, PCI, and USB/IO clock frequencies for custom configuration
•Factory-EPROM programmable output drive and slew rate for EMI customization
•MODE Enable pin for CPU_STOP</a> and PCI_STOP</a>
•SMBus serial configuration interface
•Available in space-saving 48-pin SSOP and TSSOP packages.Pinout
Specifications(Above which the useful life may be impaired. For user guide-lines, not tested.)
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
(per MIL-STD-883, Method 3015, like VDD pins tied together)DescriptionThe CY2277A is a Clock Synthesizer/Driver for Pentium, Pen-tium II, 6X86, and K6 portable PCs designed with the Intel®82430TX or similar chipsets. There are three available options as shown in the selector guide
The CY2277A outputs four CPU clocks at 2.5V or 3.3V with up to nine selectable frequencies. There are up to eight 3.3V SDRAM clocks and seven PCI clocks, running at one half the CPU clock frequency. One of the PCI clocks is free-running. Additionally, the part outputs two 3.3V USB/IO clocks at 48 MHz or 24 MHz, one 2.5V IOAPIC clock at 14.318 MHz, and two 3.3V reference clocks at 14.318 MHz. The CPU, PCI, USB, and IO clock frequencies are factory-EPROM program-mable for easy customization with fast turnaround times.
The CY2277A has power-down, CPU stop and PCI stop pins for power management control. The CPU stop and PCI stop are controlled by the MODE pin. They 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 transitions. When the CPU_STOP</a> input is asserted, the CPU outputs are driven LOW. When the PCI_STOP</a> input is asserted, the PCI outputs (except the free-running PCI clock) are driven LOW. Finally, when the PWR_DWN</a> pin is asserted, the reference oscillator and PLLs are shut down, and all outputs are driven LOW.
The CY2277A 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 en- able optimal configurations for EMI control.
CY2277A Data Sheet
