Integrated
Circuit
Systems, Inc.
AV9155C
Low Cost 20-Pin Frequency Generator
General Description
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, glitch-
free 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:
PART
AV9155C-01
AV9155C-02
AV9155C-23
AV9155C-36
DESCRIPTION
Motherboard clock generator with 16 MHz BUS CLK
Motherboard clock generator with 32 MHz BUS CLK
Features a special 40 MHz SCSI clock
Includes Pentium
frequencies
Features
•
•
•
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 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.
Block Diagram
AV9155C Rev F 12/13/00
Ô
Pentium is a trademark of Intel Corporation.
AV9155C
Pin Configuration
20-Pin DIP or SOIC
20-Pin DIP or SOIC
Pin Descriptions for AV9155C-01, -02
PIN
NUMBER
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
PIN NAME
1.843 MHz
X2
X1
VDD
GND
16 MHz/32 MHz
24 MHz
12 MHz
AGND
OE
FS2
PD#
14.318 MHz
14.318 MHz
GND
VDD
2XCPU
CPU
FS1
FS0
TYPE
Output
Output
Input
-
-
Output
Output
Output
-
Input
Input
Input
Output
Output
-
-
Output
Output
Input
Input
DESCRIPTION
1.84 MHz clock output.
Crystal connection.
Crystal connection.
Digital power supply (3.3V or 5.0V).
Digital Ground.
16 MHz (-01) or 32 MHz (-02) clock output.
24 MHz floppy disk/combination I/O clock output.
12 MHz keyboard clock output.
Analog ground (original version).
Output enable. Tristates all outputs when low. (Has internal pull-up.)
CPU clock frequency select #2. (Has internal pull-up.)
Power-down. Shuts off entire chip when low. (Has internal pull-up.)
14.318 MHz reference clock output.
14.318 MHz reference clock output.
Digital ground.
Digital power supply (3.3V or 5.0V).
2X CPU clock output.
1X CPU clock output.
CPU clock frequency select #1. (Has internal pull-up.)
CPU clock frequency select #0. (Has internal pull-up.)
2
AV9155C
Functionality
- AV9155C-01
(Using 14.318 MHz input. All frequencies in MHz.)
CLOCK#2 CPU and 2XCPU
FS2
(Pin 11)
0
0
0
0
1
1
1
1
FS1
(Pin 19)
0
0
1
1
0
0
1
1
FS0
(Pin 20)
0
1
0
1
0
1
0
1
2XCPU
(Pin 17)
8
16
32
40
50
66.66
80*
100*
CPU
(Pin 18)
4
8
16
20
25
33.33
40*
50*
PERIPHERAL CLOCKS
COMMCLK
(Pin 1)
1.843
BUSCLK
(Pin 6)
16
FDCLK
(Pin 7)
24
KBCLK
(Pin 8)
12
REFERENCE CLOCKS
REFCLK1
(Pin 13)
14.318
REFCLK2
(Pin 14)
14.318
*V
DD
minimum 3.15V.
Functionality - AV9155C-02
(Using 14.318 MHz input. All frequencies in MHz.)
CLOCK#2 CPU and 2XCPU
FS2
(Pin 11)
0
0
0
0
1
1
1
1
FS1
(Pin 19)
0
0
1
1
0
0
1
1
FS0
(Pin 20)
0
1
0
1
0
1
0
1
2XCPU
(Pin 17)
8
16
32
40
50
66.66
80*
100*
CPU
(Pin 18)
4
8
16
20
25
33.33
40*
50*
PERIPHERAL CLOCKS
COMMCLK
(Pin 1)
1.843
BUSCLK
(Pin 6)
32
FDCLK
(Pin 7)
24
KBCLK
(Pin 8)
12
REFERENCE CLOCKS
REFCLK1
(Pin 13)
14.318
REFCLK2
(Pin 14)
14.318
* V
DD
minimum 3.15V
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.
3
AV9155C
Pin Configuration
20-Pin DIP or SOIC
20-Pin DIP or SOIC
Pin Descriptions for AV9155C-23, -36
PIN
NUMBER
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
X2
X1
VDD
GND
16 MHz/15 MHz
24 MHz
12 MHz
AGND
OE
FS2
PD#
14.318 MHz
14.318 MHz
GND
VDD
2XCPU
CPU
FS1
FS0
PIN
NAME
1.843/40 MHz
TYPE
Output
Output
Input
-
-
Output
Output
Output
-
Input
Input
Input
Output
Output
-
-
Output
Output
Input
Input
DESCRIPTION
1.84 MHz (-23)/40 MHz SCSI (-36) clock output.
Crystal connection.
Crystal connection.
Digital power supply (3.3V or 5.0V).
Digital ground.
16 MHz (-23)/15 MHz (-36) clock output.
24 MHz floppy disk/combination I/O clock output.
12 MHz keyboard clock output.
Analog ground (original version).
Output enable. Tristates all outputs when low. (Has internal pull-up.)
CPU clock frequency select #2. (-23 has internal pull-up.)
Power-down. Shuts off entire chip when low. (Has internal pull-up.)
14.318 MHz reference clock output.
14.318 MHz reference clock output.
Digital ground.
Digital power supply (3.3V or 5.0V).
2X CPU clock output.
1X CPU clock output.
CPU clock frequency select #1. (-23 has internal pull-up.)
CPU clock frequency select #0. (-23 has internal pull-up.)
4
AV9155C
Functionality
- AV9155C-23
(Using 14.318 MHz input. All frequencies in MHz.)
CLOCK#2 CPU and 2XCPU
FS2
(Pin 11)
0
0
0
0
1
1
1
1
FS1
(Pin 19)
0
0
1
1
0
0
1
1
FS0
(Pin 20)
0
1
0
1
0
1
0
1
2XCPU
(Pin 17)
75*
32
60
40
50
66.66
80*
52
CPU
(Pin 18)
37.5*
16
30
20
25
33.33
40*
26
PERIPHERAL CLOCKS
COMMCLK
(Pin 1)
1.843
BUSCLK (Pin
6)
16
FDCLK
(Pin 7)
24
KBCLK
(Pin 8)
12
REFERENCE CLOCKS
REFCLK1
(Pin 13)
14.318
REFCLK2
(Pin 14)
14.318
*V
DD
minimum 3.15V
Functionality
- AV9155C-36
(Using 14.318 MHz input. All frequencies in MHz.)
CLOCK#2 CPU and 2XCPU
FS2
(Pin 11)
0
0
0
0
1
1
1
1
FS1
(Pin 19)
0
0
1
1
0
0
1
1
FS0
(Pin 20)
0
1
0
1
0
1
0
1
2XCPU
(Pin 17)
8
16
60
40
50
66.66
80*
100*
CPU
(Pin 18)
4
8
30
20
25
33.33
40*
50*
PERIPHERAL CLOCKS
SCSICLK
(Pin 1)
40
BUSCLK (Pin
6)
15
FDCLK
(Pin 7)
24
KBCLK
(Pin 8)
12
REFERENCE CLOCKS
REFCLK1
(Pin 13)
14.318
REFCLK2
(Pin 14)
14.318
*V
DD
minimum 3.15V
5
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