MK1491-14
OPTi ACPI Firestar Clock Source
Description
The MK1491-14 is a low cost, low jitter, high
performance clock synthesizer for OPTi’s
Firestar and Firestar+ chipsets for Pentium™
Processor-based mobile computer applications.
Using analog Phase-Locked Loop (PLL)
techniques, the device uses a 14.318 MHz
crystal input to produce multiple output
clocks up to 75 MHz. It provides selectable
Host and PCI local bus clocks as well as
selectable clocks for Super I/O or Universal
Serial Bus (USB). The device has up to seven
Host output clocks.
The chip has three different power down
modes that reduce power on various clocks.
Features
• Packaged in 28 pin, 150 mil wide SSOP
• Provides all critical timing for OPTi ACPI Firestar
and Firestar+
• Early Host clock of 3.5ns
• Separate VDD and skew adjust for Host 5,6, and 7
supports field upgrade to Firestar+ and new 2.5V
processors
• 48MHz USB, 24MHz SIO, and Audio clock support
• Single pin CPU(Host) slowdown to 33.3MHz
• Multiple power down modes
• Low EMI Enable pin reduces EMI radiation (patent
pending)
Block Diagram
VDD
3
FS1:0
Synch./Asynch. PCI
STOP#
SLOW#
Low EMI Enable
PS
GND
4
VDD
HOST5-7
HS
VDD
HOST1-4
Output
Buffers
HOST/PCI
Clocks
4
HOST1:4
2
Output
Buffers
Host/2
MUX
Output
Buffers
Output
Buffer
Output
Buffer
5
HOST 5, 7
EHOST6
PCI 1:5
SEL0
SEL1
33M
Fixed
Clock
F1
F2
14.31818 MHz
crystal
XI
Crystal
Oscillator
XO
Output
Buffer
14.318 MHz
MDS 1491-14 B
1
Revision 061801
Integrated Circuit Systems, Inc. • 525 Race Street • San Jose •CA •95126 • (408)295-9800tel • www.icst.com
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