Integrated
Circuit
Systems, Inc.
AV9154A
Low-Cost 16-Pin Frequency Generator
General Description
.
AV9154A
is a 0.8mm version of the industry leading AV9154.
The
Like the AV9154, the
AV9154A
is a low-cost frequency generator
designed for general purpose PC and disk drive applications. However,
because the
AV9154A
uses 0.8mm technology and the latest phase-
locked loop architecture, it offers performance advantages that
enable the device to be sold into Pentium™ systems.
The AV9154A guarantees a 45/55 duty cycle over all frequencies. In
addition, a worst case jitter of ±250ps is specified at Pentium
frequencies.
The CPU clock offers the unique feature of smooth, glitch-free
transitions from one frequency to the next, making this the ideal
device to use when slowing the CPU speed. The
AV9154A
makes a
gradual transition between frequencies so that it obeys the Intel
cycle-to-cycle timing specifications for 486 and Pentium systems.
The
AV9154A-42
and
AV9154A-43
devices offer features specifically
for green PCs. The
AV9154A-42
and -43 have a single pin that,
when pulled low, will smoothly slow the 2XCPU clock to 8 MHz.
This is ideal for dynamic DX microprocessors. The
AV9154A-43
not only has the slow clock feature, but also offers a glitch-free stop
clock for static SX microprocessors. The STOPCLK# pin, when
pulled low, enables the 2XCPU clock to go low only after completing
its last full cycle. The clock continues to run internally, and will be
output again on the first full cycle immediately following stop clock
disable.
The simultaneous 2X and 1X CPU clocks offer controlled skew to
within 500ps of each other (-42 only).
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. Consult ICS for all your clock generation needs.
Features
•
•
•
•
•
•
•
•
•
•
•
Compatible with 386, 486 and Pentium CPUs
45/55 Duty cycle
Runs up to 66 MHz at 3.3V
Single pin can slow clock to 8 MHz (on -42 and -43)
Single pin can stop the CPU clock glitch-free (on -43)
Very low jitter, ±250ps for Pentium frequencies
1X and 2X CPU clocks skew controlled to ±250ps (-42
only)
Smooth transitions between all CPU frequencies
Slow frequency ramp at power-on avoids CPU lock-up
16-pin PDIP or 150-mil skinny SOIC packages
0.8µm CMOS technology
Applications
Computer motherboards: The
AV9154A-ST
replaces crystals
and oscillators, saving board space, component cost, part
count and inventory costs. It produces a switchable CPU clock
and up to four fixed clocks to drive floppy disk, communications,
super I/O, Bus, and/or keyboard devices. The small package
and 3.3V operation is perfect for handheld computers.
Block Diagram
Pentium is a trademark of Intel Corporation
9154 Rev B 04/17/97
AV9154A
Stop Clock Feature
The
ICS9154A-43
incorporates a unique stop clock
feature compatible with static logic processors. When
the stop clock pin goes low, the 2XCPUCLK will go
low after the next occurring falling edge. When
STOPCLK again goes high, 2XCPUCLK resumes on
the next rising edge of the internal clock. This feature
enables fast, glitch-free starts and stops of the
2XCPUCLK and is guaranteed that the CPU does not
receive any short period clocks.
3
AV9154A
Pin Descriptions
Frequencies based upon 14.318 MHz input)
PIN NUMBER
PIN NAME
TYPE
DESCRIPTION
-4
4
13
5
12
8
1
16
10
-
-
-
3
2
11
-
6
-
-
7
14
15
9
-
-10
4
13
5
12
8
16
15
-
-
-
-
3
2
10
7
11
6
-
1
14
-
-
9
-26
4
13
5
12
8
1
16
10
9
-
-
3
2
11
-27
4
13
5
12
8
16
15
10
9
-
-
3
2
11
1
-42
4
13
5
12
8
1
16
9
-
15
-
3
2
10
-
6
-
-
7
11
14
-
-
-43
4
13
5
12
8
1
16
10
-
15
9
3
2
11
-
6
-
-
7
-
14
-
-
VDD
VDD
GND
GDD
AGND
FS0
FS1
FS2
OE
SLOWCLK#
STOPCLK#
X1
X2
14.318 MHz
1.84 MHz
24 MHz
16 MHz
12 MHz
8 MHz
CPUCLK
2XCPUCLK
PD#
PDFCLK#
P
P
P
P
P
I
I
I
I
I
I
I
O
O
O
O
O
O
O
O
O
I
I
Digital power (3.3 or 5V).
Digital power (3.3 or 5V).
Digital ground.
Digital ground.
Analog ground.
Frequency select 0 for CPU clock
(has internal pull-up).*
Frequency select 1 for CPU clock
(has internal pull-up).*
Frequency select 2 for CPU clock
(has internal pull-up).*
Tristates outputs when low (has internal pull-up).*
Slows 2XCPU clock to 8 MHz (active low)
(has internal pull-up).
Stops 2XCPU clock glitch-free (active low)
(has internal pull-up).
Crystal In.
Crystal Out.
14.318 MHz reference clock output.
1.84 MHz (comm) clock output.
24 MHz (floppy disk) clock output.
16 MHz clock output.
12 MHz keyboard clock output.
8 MHz keyboard clock output.
CPU clock output.
2X CPU clock output.
Power-Down All (active low) (has internal pull-up).
Power-Down Fixed Clock
(1.84, 8, 16, 24) (active low).**
6
-
7
-
14
15
-
-
6
-
7
-
-
14
-
-
Note:
Internal Pull-up Resistors.
* -04 and -10 have no pull-ups or frequency select pins
** -10 has no pull-up or Pin 9 PDFCLK
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