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PDF ICD2028 Data sheet ( Hoja de datos )

Número de pieza ICD2028
Descripción PC Motherboard Clock Generator
Fabricantes Cypress Semiconductor 
Logotipo Cypress Semiconductor Logotipo



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fax id: 35071ICD2028
ICD2028
PC Motherboard Clock Generator
Features
Eight independent clock outputs handle all clocking re-
quirements for personal computer motherboards
CPU clock frequency range:
10 MHz to 100 MHz with user-defined duty cycle
Four user-configurable outputs
Skew-free CPU clock, CPU clock ÷2, and buffered CPU
clock options on configurable outputs
Ideally suited for desktop PCs
Phase-locked loop oscillator input derived from single
14.31818 MHz crystal
Sophisticated internal loop-filter requires no external
components
Battery input maintains 32.768 kHz clock during pow-
er-down
Three-state oscillator control disables outputs for test
purposes
5V operation
Low-power, high-speed CMOS technology
Available in 20-pin SOIC package configuration
Functional Description
A modern personal computer motherboard often requires as
many as seven different crystal can oscillators. The System
Logic family of frequency synthesis parts from Cypress/IC De-
signs replaces the large number of oscillators required to build
such multi-function motherboards. These parts synthesize all
the required frequencies in a single monolithic device, thus
lowering manufacturing costs and significantly reducing the
printed circuit board space required.
The ICD2028 is a second-generation PC Motherboard Clock
Generator built on the foundation of the industry-standard and
most widely-used ICD2023. The ICD2028 offers most of the
features of the ICD2023, as well as some important enhance-
ments:
• An additional VCO
• An additional clock output
• Four customer-configured outputs which can be configured
to have
• A skew-free divided-by-two CPU clock
• An additional skew-free CPU clock
• User-definable CPUCLK output duty cycle
Because today’s desktop PCs must support a myriad of new
requirements, and each company’s implementation tends to
be unique, the most important new feature of the ICD2028 is
its ability to tailor four of the outputs to the individual needs of
today’s system logic design engineer, and to configure the
CPUCLK duty cycle for special microprocessor needs.
The ICD2028 was specifically designed to support such de-
manding clock requirements as:
• 486 and Pentium™ microprocessors both with and without
clock doublers
• New single-chip system logic chip sets
• Super I/O combo chips
• New high-density floppy disk drive controllers
The ICD2028 consists of two crystal-controlled oscillators,
three phase-locked loops, and eight different outputs in a sin-
gle package. To sum up, the greatest asset of the ICD2028 lies
in its ability to serve as the single source of all clocking require-
ments in modern desktop PCs.
Pin Configuration
SOIC
Top View
32XOUT
32.768 kHz
CLKC
VDD
GND
XTALIN
XTALOUT
SYSBUS
CLKD
CPUCLK
1
2
3
4
5
6
7
8
9
10
20
19
18
17
16
15
14
13
12
11
32XIN
VBATT
OE
S2
AVDD
S1
S0
24.0MHz
CLKA
CLKB
ICD2028–1
Cypress Semiconductor Corporation • 3901 North First Street • San Jose • CA 95134 • 408-943-2600
June 1994 – Revised April 1995

1 page




ICD2028 pdf
ICD2028
User-Selectable Clock Options
System and Utility Clock Selection
The heart of the ICD2028 is the rich set of frequencies which
are generated internally, encompassing most known system
logic motherboard requirements. From this set of outputs, the
user may select four output frequencies.
Through a proprietary technique, Cypress/IC Designs can
quickly configure samples of any desired output pin configura-
tion. The configuration process involves no NRE (non-recur-
ring engineering) charges or prototype delays, as are com-
monly associated with masked ROM changes. Samples of
user-configured ICD2028s can generally be made available in
24 hours.
Tables 1 and 2 list all the available internally generated system
clocks on the CLKA, CLKB, CLKC, and CLKD outputs, as well
as the Utility PLL output.
Table 1. System Clock Options
Clock Function Desired Freq. Actual Freq.
(MHz)
(MHz)
Error (PPM) Clock Source Available on Pin (s)
SYSCLK PLL
Super Floppy
Floppy Disk
Internal Bus
System Bus
Keyboard
Bus Clock
Alt. Comm. Port
Serial Port
Special CLK
96.000
48.000
32.000
24.000
16.000
14.318
12.000
9.600
8.000
4.770
3.686
1.843
1.000
95.870
47.935
31.957
23.967
15.978
14.318
11.984
9.587
7.989
4.773
3.687
1.844
0.999
1361
1361
1361
1361
1361
0
1361
1361
1361
572
242
242
1361
SYSCLK
SYSCLK/2
X
SYSCLK/3 X X
SYSCLK/4 X
SYSCLK/6
XXX
fREF
SYSCLK/8
X
XX
SYSCLK/10 X
X
SYSCLK/12 X X
X
fREF/3
SYSCLK/26
X
X
X
SYSCLK/52
X
SYSCLK/96
X
X
5

5 Page





ICD2028 arduino
ICD2028: Thursday, July 14, 1994
Revision: April 27, 1995
Switching Waveforms (continued)
Selection Timing
S0–S2
Original Frequency
(Internal)
MUXREF
VCO Settle Time
tMUXREF
ICD2028
New Frequency
CPUCLK
tfreq1
tA
t(REF)
tB
tfreq2
ICD2028–9
Ordering Information
Ordering Code
ICD2028
Package
Name
Package Type
S5 20-Pin SOIC
Operating
Range
C=0°C to +70°C @ VDD=5V
Example: Order ICD2028SC-2 for the ICD2028, 20-pin plastic
SOIC, 5V operating range device which uses the standard
configuration code -2 (486 compatibility with CPUCLK/2 sup-
port). See Table 6 for details on the standard configurations.
Standard packaging is in a surface-mount configuration. The
ICD2028 is also available in a through-hole DIP configuration
by special order. Please contact your Cypress representative
for current availability and lead times.
Document #: 38-00400
Package Diagram
20-Lead (300-Mil) Molded SOIC S5
© Cypress Semiconductor Corporation, 1995. The information contained herein is subject to change without notice. Cypress Semiconductor Corporation assumes no responsibility for the use
of any circuitry other than circuitry embodied in a Cypress Semiconductor product. Nor does it convey or imply any license under patent or other rights. Cypress Semiconductor does not authorize
its products for use as critical components in life-support systems where a malfunction or failure may reasonably be expected to result in significant injury to the user. The inclusion of Cypress
Semiconductor products in life-support systems application implies that the manufacturer assumes all risk of such use and in doing so indemnifies Cypress Semiconductor against all charges.

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