IMISG509
April 1996
REDUCED EMI CLOCK CHIP
CMOS LSI
SPECTRUM SPREAD CLOCK GENERATOR
PRODUCT FEATURES
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Generates CPU clock signals for microprocessor
systems
Reduces measured EMI by 10 dB nominal
4V to 6V operating supply range
Supports CPUs from all major manufacturers.
Wide range of selectable output frequencies
including 60, 50, 48, 40, 33.3, 16.7
Single, low-cost
frequency
crystal
used
as
reference
PRODUCT DESCRIPTION
The IMISG509 is a spectrum spread clock generator
specially designed for personal computers, laser
printers and other digital systems. IMISG509 uses a
patented concept to generate popular clock frequencies
that are intentionally broadbanded to reduce
electromagnetic interference. The radiated emissions,
associated with either the clock, harmonics or any
signals derived from the clock, nominally reduced by
10 dB and could significantly reduce the cost of
complying with the regulatory requirements.
PRCLK is the broadbanded output and can be
programmed by the PRCLK Frequency Selection Table
on Page 2. A single, low cost external crystal is
required as reference frequency for the synthesizer.
The output modulation function can be disabled when
the SSON pin is high.
Glitch-free switching
50% duty cycle
TTL or CMOS compatible outputs with 6 mA drive
capability
Low, short and long-term jitter
16 pin P-DIP and 16 Pin SOIC (300 mil body)
package options
CONNECTION DIAGRAM
VDD
OSCin
OSCout
VSS
MPSEL
AVDD
S0
S1
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
S3
VDD
MPCLK
VSS
PRCLK
AVSS
LF1
SSON
BLOCK DIAGRAM
3
44.2 MHz
2
REF
/4 OR /12
14 MPCLK
MPSEL
5
10
7
8
16
9
SPECTRUM
SPREAD
CLOCK GEN
LF
S0
S1
S3
SSON
/2
12 PRCLK
APPLICATIONS
IMISG509 eliminates the need for multiple oscillators
and generates the CPU clock signals for personal
computers, laser printers and other digital systems.
Supports CPUs from all major manufacturers.
INTERNATIONAL MICROCIRCUITS, INC. 525 LOS COCHES ST.
MILPITAS, CA 95035 TEL: 408-263-6300 FAX 408-263-6571
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