Integrated
Circuit
Systems, Inc.
9154A
Low-Cost 16-Pin Frequency Generator
General Description
The
9154A
is a 0.8mm version of the industry leading 9154.
Like the 9154, the
9154A
is a low-cost frequency generator
designed for general purpose PC and disk drive applications.
However, because the
9154A
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 9154A 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
9154A
makes a gradual transition between frequencies so
that it obeys the Intel cycle-to-cycle timing specifications for
486 and Pentium systems.
The
9154A-42
and
9154A-43
devices offer features
specifically for green PCs. The
9154A-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
9154A-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 150-mil skinny SOIC packages
0.8µm CMOS technology
Applications
Computer motherboards: The
9154A
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
0174E—03/18/08
Integrated
Circuit
Systems, Inc.
9154A
Pin Configuration
16-SOIC
9154A-27CS16
16-SOIC
9154A-42CS16
Description of new pin:
SLOWCLK# forces 2XCPUCLK
output to ramp smoothly to 8MHz
and CPUCLK output to 4 MHz
when pulled low.
16-SOIC
9154A-43CS16
Description of new pis:
SLOWCLK# forces 2XCPUCLK
output to ramp smoothly to 8MHz
when pulled low. STOPCLK#
provides gilitch-free stop of the
2XCPUCLK output when pulled
low. When raised back high, the
2XCPUCLK
output
clock
resumes full speed operation (no
clock frequency ramp up since
the internal VCO is not stopped).
16-SOIC
9154A-04CS16
E
T
E
L
O
S
B
O
16-SOIC
9154A-26CS16
16-SOIC
9154A-10CS16
0174E—03/18/08
2
Integrated
Circuit
Systems, Inc.
9154A
Pin Descriptions
Frequencies based upon 14.318 MHz input)
-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
PIN NUMBER
-26
-27
4
4
13
13
5
5
12
12
8
8
1
16
10
9
-
-
3
2
11
6
-
7
-
14
15
-
-
16
15
10
9
-
-
3
2
11
1
6
-
7
-
-
14
-
-
PIN NAME
-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#
TYPE
P
P
P
P
P
I
I
I
I
I
I
I
O
O
O
O
O
O
O
O
O
I
I
DESCRIPTION
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).*
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
0174E—03/18/08
4
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