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參數(shù)資料
| 型號(hào)： | CY2254ASC-2 |
| 廠商： | CYPRESS SEMICONDUCTOR CORP |
| 元件分類： | XO, clock |
| 英文描述： | Pentium Processor Compatible Clock Synthesizer/Driver |
| 中文描述： | 66.66 MHz, PROC SPECIFIC CLOCK GENERATOR, PDSO28 |
| 封裝： | 0.300 INCH, SOIC-28 |
| 文件頁(yè)數(shù)： | 1/8頁(yè) |
| 文件大?。?/td> | 94K |
| 代理商： | CY2254ASC-2 |
Pentium
Processor Compatible
Clock Synthesizer/Driver
Freq. stability = 0.01% (max.)
Output duty cycle 45% min. to 55% max.
Test mode support (
1 option only)
3.3V or 5.0V operation
Internal pull-up resistors on S0, S1, and OE inputs
CY2254A
Cypress Semiconductor Corporation
Document #: 38-07203 Rev. *A
3901 North First Street
San Jose
CA 95134
Revised December 14, 2002
408-943-2600
4A
Features
Multiple clock outputs to meet requirements of most
Pentium
motherboards
—
Four pin-selectable CPU clocks @ 66.66 MHz, 60.0
MHz, and 50.0 MHz for support of Intel Triton
PCIset
based PC
—
55.0 MHz pin-selectable CPU clock also available (
2
option only)
—
Six PCI clocks at 1/2 CPU Clock frequency
—
One I/O clock @ 24 MHz
—
One Keyboard Controller clock @ 12 MHz (
1 option)
or one Universal Serial Bus clock @ 48 MHz
(
2 option)
—
Two Ref. clocks @ 14.318 MHz
—
Ref. 14.318 MHz Xtal oscillator input
CPU clock jitter < 200 ps cycle-to-cycle
Low skew outputs
—
< 250 ps between CPU clocks
—
< 250 ps between PCI clocks
—
< 500 ps between CPU and PCI clocks (
2 option)
—
CPU clock leads PCI clock by +1 ns min. to +4 ns
max. (
1 option)
Functional Description
The CY2254A is a Clock Synthesizer/Driver that provides the
multiple clocks required for a Pentium-based PC. The
CY2254A has low-skew outputs (< 250 ps between the CPU
Clocks, < 250 ps between the PCI Clocks). In addition, the
CY2254A CPU clock outputs have less than 200 ps cy-
cle-to-cycle jitter. Finally, both the PCI and CPU clock outputs
meet the 1 V/ns slew rate requirement of a Pentium proces-
sor-based system.
The CY2254A accepts a 14.318 MHz reference signal as its
input. The CY2254A has 2 PLLs, one of which generates the
CPU and PCI clocks, and the other generates the I/O and Key-
board Controller or USB clocks. The CY2254A runs off either
a 3.3V or 5V supply.
The CY2254A is available in two options. The
1 option sup-
ports the Intel Triton PCIset and provides a 12 MHz keyboard
clock on pin 25. The
2 option provides a 48 MHz USB clock
on pin 25 and supports the Cyrix
M1 processor.
Intel and Pentium are registered trademarks of Intel Corporation.
Triton is a trademark of Intel Corporation.
Cyrix is a registered trademark of Cyrix Corporation.
Pin Configuration
Logic Block Diagram
XTALOUT
XTALIN
REF0 (14.318 MHz)
14.318
MHz
OSC.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
24
23
22
21
25
28
27
26
Top View
SOIC
V
DD
XTALIN
XTALOUT
V
SS
OE
CPUCLK0
CPUCLK1
V
DD
CPUCLK2
CPUCLK3
V
SS
S1
S0
V
DD
REF0
REF1
V
DD
SEEBELOW
IOCLK
V
SS
PCICLK2
PCICLK3
V
DD
PCICLK4
PCICLK5
V
SS
PCICLK1
PCICLK0
REF1 (14.318 MHz)
IOCLK (24 MHz)
CPUCLK0
CPUCLK1
CPUCLK2
CPUCLK3
PCICLK0
SYS
PLL
CPU
PLL
ROM
S0
S1
OE
÷
2
DELAY
PCICLK1
PCICLK2
PCICLK3
PCICLK4
PCICLK5
USBCLK (48 MHz)
KBDCLK (12 MHz)
÷
2
÷
2
1
2
OPTION
PIN 25
KBDCLK
12 MHz
USBCLK
48 MHz
1 option only
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相關(guān)代理商/技術(shù)參數(shù) |
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| CY2255 | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:CPU System Clock Generator |
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