IMISG501
March 1996
PATENT PENDING
SYSTEM CLOCK CHIP
REDUCED EMI CLOCK GENERATOR
PRODUCT FEATURES
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Generates CPU Clock Signals for Microprocessor
Systems
Reduces Measured EMI by 10 db nominal
4V to 7V Operating Supply Range
Supports 80286-, 80386-, 80486-, Pentium鈩? and
29000-based designs
Wide range of selectable output frequencies
including 50, 25, 20 and 10 Mhz
single, low
frequency
cost
crystal
used
as
reference
PRODUCT DESCRIPTION
The IMISG501 is a spectrum spread clock generator
specially designed for personal computers, laser
printers and other digital systems. IMISG501 uses a
patent pending concept to generate popular clock
frequencies that are intentionally broadbanded to
reduce electromagnetic interference. IMISG501
attenuates the radiated emission amplitudes from
products associated with either the clock harmonics or
any signals derived from the clock signals nominally 10
db and could significantly reduce the cost of complying
with the regulatory requirements.
PRCLK is the broadbanded output and can be
programmed to generate 50, 25, 20 and 10 Mhz with
S0 and S1 pins. A single, low cost external crystal is
required as reference frequency for the synthesizer.
Output modulation function can be turned off with the
SSON pin. Several power down modes add the
flexibility to operate the device in a completely static
mode to reduce standby currents and simplify system
board tests.
Glitch-free switching
50% duty cycle
Power down mode for low power consumption
TTL or CMOS compatible outputs with 6mA drive
capability
Low, short- and long-term jitter
16 PDIP and 16 Pin SOIC (300 mil body) package
options
PDIP/SOIC 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
TEST
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
LF
S0
S1
TEST
SSON
APPLICATIONS
SPECTRUM
SPREAD
CLOCK GEN
/2
12
PRCLK
IMISG501 eliminates the need for multiple oscillators
and generates the CPU clock signals for personal
computers, laser printers and other digital systems.
Supports 8086-, 80286-, 80386-, 80486-, Pentium鈩?
and 29000-based designs. IMISG501 can be used with
laptop or notebook computers to save power by
running the system slower than normal CPU speeds or
completely disabling the clocks in standby mode.
INTERNATIONAL MICROCIRCUITS, INC. 525 LOS COCHES ST.
MILPITAS, CA 95035 TEL: 408-263-6300 FAX 408-263-6571
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