Integrated
Circuit
Systems, Inc.
General Description
Features
AV9155
Block Diagram
9155 Rev B 8/24/98
Low Cost 20-Pin Frequency Generator
The AV9155 is a low cost frequency generator designed spe-
cifically for desktop and notebook PC applications. Its CPU
clocks provide all necessary CPU frequencies for 286, 386 and
486 systems, including support for the latest speeds of proces-
sors. 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, glitch-free
transitions from one frequency to the next, making this ideal
device to use whenever slowing the CPU speed. The AV9155
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 AV9155. 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 AV9155 is a third generation
device, and uses ICSs patented analog CMOS phase-locked
loop technology for low phase jitter. ICS offers 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.
PART
DESCRIPTION
AV9155C-01
Motherboard clock generator with 16 MHz BUS CLK
AV9155C-02
Motherboard clock generator with 32 MHz BUS CLK
AV9155C-23
Includes Pentium
TM
frequencies
AV9155C-36
Features a special 40 MHz SCSI clock
2
AV9155
Pin Configuration
20-Pin DIP or SOIC
20-Pin DIP or SOIC
Pin Descriptions for AV 9155-01, 9155-02
PIN
N UM BER
PIN N AM E
TYPE
DESC RIPTIO N
1
1.843 M Hz
O utput
1.84 M Hz clock output.
2
X2
O utput
C rystal connection.
3
X1
Input
C rystal connection.
4
VDD
-
Digital power supply (3.3V or 5.0V).
5
GN D
-
Digital Ground.
6
16 M Hz/32 M Hz
O utput
16 M Hz (-01) or 32 M Hz (-02) clock output.
7
24 M Hz
O utput
24 M Hz floppy disk/combination I/O clock output.
8
12 M Hz
O utput
12 M Hz keyboard clock output.
9
AGN D
-
Analog ground (original version).
10
O E
Input
O utput enable. Tristates all outputs when low. (Has internal pull-up.)
11
FS2
Input
C PU clock frequency select #2. (Has internal pull-up.)
12
PD#
Input
Power-down. Shuts off entire chip when low. (Has internal pull-up.)
13
14.318 M Hz
O utput
14.318 M Hz reference clock output.
14
14.318 M Hz
O utput
14.318 M Hz reference clock output.
15
GN D
-
Digital ground.
16
VDD
-
Digital power supply (3.3V or 5.0V).
17
2XC PU
O utput
2X C P U clock output.
18
C PU
O utput
1X C PU clock output.
19
FS1
Input
C PU clock frequency select #1. (Has internal pull-up.)
20
FS0
Input
C PU clock frequency select #0. (Has internal pull-up.)
3
AV9155
Functionality
- AV9155-01
(Using 14.318 MHz input. All frequencies in MHz.)
CLOCK#2 CPU and 2XCPU
*5V only.
PERIPHERAL CLOCKS
REFERENCE CLOCKS
Functionality - AV9155-02
(Using 14.318 MHz input. All frequencies in MHz.)
CLOCK#2 CPU and 2XCPU
PERIPHERAL CLOCKS
REFERENCE CLOCKS
Frequency Transitions
A key feature of the AV9155 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 AV9155 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 AV9155 with a clock.
COMMCLK
(Pin 1)
BUSCLK
(Pin 6)
FDCLK
(Pin 7)
KBCLK
(Pin 8)
1.843*
16*
24*
12*
COMMCLK
(Pin 1)
BUSCLK
(Pin 6)
FDCLK
(Pin 7)
KBCLK
(Pin 8)
1.843*
32*
24*
12*
REFCLK1
(Pin 13)
REFCLK2
(Pin 14)
14.318
14.318
REFCLK1
(Pin 13)
REFCLK2
(Pin 14)
14.318
14.318
FS2
(Pin 11)
FS1
(Pin 19)
FS0
(Pin 20)
2XCPU
(Pin 17)
CPU
(Pin 18)
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
16
32
40
50
66.66
80*
100*
4
8
16
20
25
33.33
40*
50*
FS2
(Pin 11)
FS1
(Pin 19)
FS0
(Pin 20)
2XCPU
(Pin 17)
CPU
(Pin 18)
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
16
32
40
50
66.66
80*
100*
4
8
16
20
25
33.33
40*
50*
*5V only.
4
AV9155
Pin Configuration
Pin Descriptions for AV9155-23, -36
20-Pin DIP or SOIC
20-Pin DIP or SOIC
PIN
NUMBER
PIN
NAME
TYPE
DESCRIPTION
1
1.843/40 MHz
Output
1.84 MHz (-23)/40 MHz SCSI (-36) clock output.
2
X2
Output
Crystal connection.
3
X1
Input
Crystal connection.
4
VDD
-
Digital power supply (+5V)
5
GND
-
Digital ground.
6
16 MHz/15 MHz
Output
16 MHz (-23)/15 MHz (-36) clock output.
7
24 MHz
Output
24 MHz floppy disk/combination I/O clock output.
8
12 MHz
Output
12 MHz keyboard clock output.
9
AGND
-
Analog ground (original version).
10
OE
Input
Output enable. Tristates all outputs when low. (Has internal pull-up.)
11
FS2
Input
CPU clock frequency select #2. (-23 has internal pull-up.)
12
PD#
Input
Power-down. Shuts off entire chip when low. (Has internal pull-up.)
13
14.318 MHz
Output
14.318 MHz reference clock output.
14
14.318 MHz
Output
14.318 MHz reference clock output.
15
GND
-
Digital ground.
16
VDD
-
Digital power supply (3.3V or 5.0V).
17
2XCPU
Output
2X CPU clock output.
18
CPU
Output
1X CPU clock output.
19
FS1
Input
CPU clock frequency select #1. (-23 has internal pull-up.)
20
FS0
Input
CPU clock frequency select #0. (-23 has internal pull-up.)
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