IMISG502
April 1996
SYSTEM CLOCK CHIP
CMOS LSI
SPECTRUM SPREAD CLOCK
PRODUCT FEATURES
n
n
n
n
n
n
n
n
n
n
n
n
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 40, 33.3, 16.7
Single, Low Cost Crystal Used as Reference
Frequency
Glitch-Free Switching
50% Duty Cycle
Power Down Mode for Low Power Consumption
TTL or CMOS Compatible Outputs with 6 mA Drive
Capability
Low, Short and Long Term Jitter (cycle-to-cycle jitter
less than 50 ps)
16 PIN PDIP and 16 PIN SOIC (300 mil body)
package options
PRODUCT DESCRIPTION
The IMISG502 is a spectrum spread clock generator
specially designed for personal computers, laser
printers and other digital systems. IMISG502 uses a
patented concept to generate popular clock frequencies
that are intentionally broadbanded to reduce
electromagnetic
interference.
The
IMISG502
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 40, 33.3, 16.7 and 12 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.
P-DIP/SOIC 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
LF
S0
S1
TEST
SSOR
5
10
7
8
16
9
APPLICATIONS
SPECTRUM
SPREAD
CLOCK
GEN
The IMISG502 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. IMISG502 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.
/2
12
PRCLK
INTERNATIONAL MICROCIRCUITS, INC. 525 LOS COCHES ST.
MILPITAS, CA 95035 TEL: 408-263-6300 FAX 408-263-6571
Page
1
of 7
1
2
3
4
5
6
7
