Y2277A
CY2277A
Pentium®/II, 6x86, K6 Clock Synthesizer/Driver for Desktop/
Mobile PCs with Intel® 82430TX and 2 DIMMs or 3 SO-DIMMs
82430TX or similar chipsets. There are three available options
as shown in the selector guide
Features
• Mixed 2.5V and 3.3V operation
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
• Complete clock solution to meet requirements of
Pentium®, Pentium® II, 6x86, or K6 motherboards
— Four CPU clocks at 2.5V or 3.3V
— Up to eight 3.3V SDRAM clocks
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.
— 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
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 input is asserted, the CPU outputs are driven
LOW. When the PCI_STOP input is asserted, the PCI outputs
(except the free-running PCI clock) are driven LOW. Finally,
when the PWR_DWN pin is asserted, the reference oscillator
and PLLs are shut down, and all outputs are driven LOW.
• 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 and PCI_STOP
• SMBus serial configuration interface
• Available in space-saving 48-pin SSOP and TSSOP
packages.
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
enable optimal configurations for EMI control.
Functional Description
The CY2277A is a Clock Synthesizer/Driver for Pentium,
Pentium II, 6X86, and K6 portable PCs designed with the Intel®
.
Pin Configuration
Top View
Logic Block Diagram
IOAPIC (14.318 MHz)
VDDQ2
REF1
REF0
AV
1
48
47
46
45
44
43
42
41
DD
2
PWR_SEL
REF [0–1]
(14.318)
XTALIN
3
14.318
MHz
OSC.
V
V
SS
DDQ2
XTALIN
XTALOUT
MODE
4
IOAPIC
XTALOUT
5
PWR_DWN
STOP
LOGIC
CPU
PLL
CPUCLK[0–3]
6
V
SS
V
CPUCLK0
CPUCLK1
7
DDQ3
PCICLK_F
PCICLK0
8
VDDCPU
9
V
40
39
38
37
36
35
34
33
32
31
DDCPU
V
SS
10
11
SDRAM[0–5]
CPUCLK2
CPUCLK3
SEL
EPROM
PCICLK1
PCICLK2
12
13
V
SS
SDRAM0
SDRAM1
MODE
SDRAM6/CPU_STOP
SDRAM7/PCI_STOP
PCICLK3
PCICLK4
SYS
PLL
14
15
16
17
18
19
20
21
22
23
24
V
V
DDQ3
DDQ3
PCICLK5
V
SDRAM2
SDRAM3
/2
SS
SEL
V
SS
Delay
SDATA
SCLK
30
29
28
27
26
25
SDRAM4
SDRAM5
PWR_DWN
STOP
LOGIC
PCI[0–5]
V
V
DDQ3
DDQ3
PCICLK_F
USBCLK/IOCLK
USBCLK/IOCLK
SDRAM6/CPU_STOP
SDRAM7/PCI_STOP
SERIAL
INTERFACE
CONTROL
LOGIC
SCLK
Divide and
Mux Logic
USBCLK/IOCLK[0:1]
V
AV
DD
SS
SDATA
Rev 1.0, November 25, 2006
2200 Laurelwood Road, Santa Clara, CA 95054
Page 1 of 18
Tel:(408) 855-0555 Fax:(408) 855-0550
www.SpectraLinear.com