IMISG508
May 1996
REDUCED EMI CLOCK CHIP
CMOS LSI
SPECTRUM SPREAD CLOCK GENERATOR
PRODUCT FEATURES
鎂
鎂
鎂
鎂
鎂
鎂
鎂
鎂
鎂
鎂
鎂
鎂
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 40, 30, 25, and 16.7 MHz.
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
16 Pin PDIP and 16 Pin SOIC (300 mil Body)
Package Options
PRODUCT DESCRIPTION
The IMISG508 is a spectrum spread clock generator
specially designed for personal computers, laser
printers and other digital systems. IMISG508 uses a
patented concept to generate popular clock frequencies
that are intentionally boradbanded to reduce
electromagnetic interference. IMISG508 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 by the PRCLK Frequency Selection Table
on page 2. 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.
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
TS
VDD
MPCLK
VSS
PRCLK
AVSS
LF1
SSON
BLOCK DIAGRAM
3
44.2
MHz
2
REF
/4 or /12
14
MPCLK
APPLICATIONS
MPSEL 5
LF 10
S0 7 SPECTRUM
SPREAD
S1 8
CLOCK GEN
TS 16
SSON
9
The IMISG508 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.
IMISG508 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.
12
/2
PRCLK
INTERNATIONAL MICROCIRCUITS, INC. 525 LOS COCHES ST.
MILPITAS, CA 95035 TEL: 408-263-6300 FAX 408-263-6571
Rev. 1.0
Page 1 of 7
1
2
3
4
5
6
7
