MK1442/MK1443
SCSI and Ethernet Clock Source
Description
The MK1442/3 are the ideal way to generate
clocks for desktop computer motherboards and
LAN workstations. Using analog Phase-Locked
Loop (PLL) techniques, the devices accept a
14.318 MHz crystal input to produce multiple
output clocks up to 100 MHz. They provide
2XCPU, CPU, floppy controller, keyboard,
system, SCSI and Ethernet clocks. The MK1442/3
are perfect for new Pentium™ Processor, PCI bus
and 486 systems. The devices can operate at 5V or
3.3V up to and including 80MHz on the CPU
clock.
The devices are identical except the MK1442 has
an Output Enable (OE) pin that tri-states all
outputs when taken low, and the MK1443 has an
extra 14.318 MHz clock.
Features
• Provides exact frequency Ethernet and SCSI clocks
• 5V or 3.3V (up to 80MHz) operation
• Output clock frequencies up to 100 MHz
• Pentium™ Processor compatible timing
• 486 compatible smooth frequency transitions
• Seven or eight output clocks
• Compatible with X86 and 680X0 CPUs
• Skew controlled 2X and 1X CPU to within 250ps
• Packaged in 16 pin skinny SOIC or PDIP
• Duty cycle of 47.5/52.5 up to 66.66 MHz
• Duty cycle of 45/55 up to 100 MHz
• Total of 15 different selectable CPU frequencies
• Tri-state outputs for board level testing
• 25mA drive capability at TTL levels
• Keyboard frequencies of 12MHz (-01),
8MHz (-02), or 16MHz (-03)
• Advanced, low power CMOS process
• MK1442 - output enable
• MK1443 - two 14.318 MHz outputs
Block Diagram
VDD
GND
CPUS0
CPUS1
Output
Buffer
2XCPU
CPU
8.00, 12.00,
or 16.00 MHz
24.00 MHz
40.000 MHz
20.000 MHz
14.318 MHz
(MK1443 only)
14.318 MHz
÷2
Clock Synthesis
and Control
Circuitry
Output
Buffer
Output
Buffer
Output
Buffer
Output
Buffer
14.318 MHz
crystal
X1
Output
Buffer
Output
Buffer
Output
Buffer
Crystal
Oscillator
X2
OE (all outputs, MK1442 only)
1
Revision 111500
Printed 11/15/00
Integrated Circuit Systems, Inc. • 525 Race Street • San Jose • CA • 95126 •(408)297-1201tel • www.icst.com
MDS 1442/3 E
ICS [ INTEGRATED CIRCUIT SYSTEMS ]
