鈥?Eight 3.3V sync. PCI clocks, one free-running
鈥?Three 3.3V Ref. clocks at 14.318 MHz
鈥?/div>
Factory-EPROM programmable output drive and
slew rate
鈥?Factory-EPROM programmable CPU clock frequencies
for custom configurations
鈥?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 provid-
ed 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 out-
puts 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 refer-
ence 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)
鈥?
4
8
2
2
鈥?/div>
3
1.5鈭?.0 ns
鈥?/div>
N/A
-1
-2
CPU_STOP
XTALIN
XTALOUT
14.318
MHz
OSC.
CPU
PLL
Divider
STOP
LOGIC
鈥?1S
4
8
2
2
鈥?/div>
3
1.5鈭?.0 ns
鈥?/div>
鈭?.6%
APIC [0:1]
V
DDAPIC
REF [0-2]
V
DDREF
CPUCLK [0-3]
V
DDCPU
PCICLK_F
鈥?1S
4
8
2
鈥?/div>
2
3
1.5鈭?.0 ns
2.0鈥?.5 ns
鈭?.6%
Logic Block Diagram
PWR_DWN
SEL0
SEL1
SEL100
SEL_SS
PCI_STOP
SYS PLL
Delay
STOP
LOGIC
EPROM
V
DDPCI
PCI [1-7]
V
DDPCI
USBCLK [0:1]
V
DDUSB
Pentium is a registered trademark of Intel Corporation.
Cypress Semiconductor Corporation
Document #: 38-07207 Rev. *A
鈥?/div>
3901 North First Street
鈥?/div>
San Jose
鈥?/div>
CA 95134 鈥?408-943-2600
Revised December 08, 2002
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