Integrated
Circuit
Systems, Inc.
General Description Features
AV9155C
Block Diagram
AV9155C Rev F 12/13/00
Low Cost 20-Pin Frequency Generator
The AV9155C is a low cost frequency generator designed
specifically for desktop and notebook PC applications with
either 3.3V or 5.0V power supply voltage. Its CPU clocks
provide all necessary CPU frequencies for 286, 386 and 486
systems, including support for the latest speeds of processors.
The device uses a 14.318 MHz crystal to generate the CPU
and all peripheral clocks for integrated desktop motherboards.
The dual 14.318 MHz clock outputs allows one output for the
system and one to be the input to an ICS graphics frequency
generator such as the AV9194.
The CPU clock offers the unique feature of smooth, glitchfree transitions from one frequency to the next, making this
ideal device to use whenever slowing the CPU speed. The
AV9155C makes a gradual transition between frequencies, so
that it obeys the Intel cycle-to-cycle timing specification for
486 systems. The simultaneous 2X and 1X CPU clocks offer
controlled skew to within 1.5ns (max) of each other.
ICS offers several versions of the AV9155C. The different
devices are shown below:
• Compatible with 286, 386, and 486 CPUs
• Supports turbo modes
• Generates communications clock, keyboard clock,
floppy disk clock, system reference clock, bus clock
and CPU clock
• Output enable tristates outputs
• Up to 100 MHz at 5V or 3.3V
• 20-pin DIP or SOIC
• All loop filter components internal
• Skew-controlled 2X and 1X CPU clocks
• Power-down option
ICS has been shipping motherboard frequency generators
since April 1990, and is the leader in the area of multiple
output clocks on a single chip. The AV9155C is a third
generation device, and uses ICS’s patented analog CMOS
phase-locked loop technology for low phase jitter. ICS of fers
a broad family of frequency generators for motherboards,
graphics and other applications, including cost-effective
versions with only one or two output clocks. Consult ICS for
all of your clock generation needs.
Pentium is a trademark of Intel Corporation.
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2
A V9155C
Pin Configuration
20-Pin DIP or SOIC
20-Pin DIP or SOIC
Pin Descriptions for A V9155C-01, -02
NIP
REBMUN
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3
AV9155C
Functionality - A V9155C-01
(Using 14.318 MHz input. All frequencies in MHz.)
CLOCK#2 CPU and 2XCPU
*VDD minimum 3.15V.
PERIPHERAL CLOCKS
REFERENCE CLOCKS
Functionality - A V9155C-02
(Using 14.318 MHz input. All frequencies in MHz.)
CLOCK#2 CPU and 2XCPU
* VDD minimum 3.15V
PERIPHERAL CLOCKS
REFERENCE CLOCKS
Frequency Transitions
A key feature of the AV9155C is its ability to provide smooth,
glitch-free frequency transitions on the CPU and 2XCPU
clocks when the frequency select pins are changed. These
frequency transitions do not violate the Intel 486 specification
of less than 0.1% frequency change per clock period.
Using an Input Clock as Reference
The AV9155C is designed to accept a 14.318 MHz crystal as
the input reference. With some external changes, it is possible
to use a crystal oscillator or clock input. Please see application
note AN04 for details on driving the AV9155C with a clock.
KLCMMOC
)1niP(
KLCSUB
)6niP(
KLCDF
)7niP(
KLCBK
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348.1614221
KLCMMOC
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KLCSUB
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KLCDF
)7niP(
KLCBK
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348.1234221
1KLCFER
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2KLCFER
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813.41813.41
1KLCFER
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2KLCFER
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813.41813.41
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0SF
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UPC
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0
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1
1
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0
1
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1
0
1
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1
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1
0
1
8
61
23
04
05
66.66
*08
*001
4
8
61
02
52
33.33
*04
*05
2SF
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1SF
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0SF
)02niP(
UPCX2
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0
0
0
0
1
1
1
1
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
8
61
23
04
05
66.66
*08
*001
4
8
61
02
52
33.33
*04
*05
4
A V9155C
Pin Configuration
Pin Descriptions for A V9155C-23, -36
20-Pin DIP or SOIC
20-Pin DIP or SOIC
NIP
REBMUN
NIP
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5
AV9155C
CLOCK#2 CPU and 2XCPU
*V
DD
minimum 3.15V
PERIPHERAL CLOCKS
REFERENCE CLOCKS
CLOCK#2 CPU and 2XCPU
*VDD minimum 3.15V
PERIPHERAL CLOCKS
REFERENCE CLOCKS
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2KLCFER
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2KLCFER
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813.41813.41
2SF
)11niP(
1SF
)91niP(
0SF
)02niP(
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0
0
0
0
1
1
1
1
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
8
61
06
04
05
66.66
*08
*001
4
8
03
02
52
33.33
*04
*05
Functionality - A V9155C-23
(Using 14.318 MHz input. All frequencies in MHz.)
Functionality - A V9155C-36
(Using 14.318 MHz input. All frequencies in MHz.)
2SF
)11niP(
1SF
)91niP(
0SF
)02niP(
UPCX2
)71niP(
UPC
)81niP(
0
0
0
0
1
1
1
1
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
*57
23
06
04
05
66.66
*08
25
*5.73
61
03
02
52
33.33
*04
62