Integrated
Circuit
Systems, Inc.
ICS9131
32 KhZ Motherboard Frequency Generator
General Description
The
ICS9131
offers a tiny footprint solution for generating
a selectable CPU clock from a 32.768 kHz crystal. The device
allows a variety of microprocessors to be clocked by changing
the state of address lines FS0, FS1, and FS2. The
ICS9131
is
the ideal solution for replacing high speed oscillators and for
reducing clock speeds to save power in computers. The
device provides smooth, glitch-free frequency transitions so
that the CPU can continue to operate during slow down or
speed up. The rate of frequency change makes the
ICS9131
compatible with all 386DX, 386SX, 486DX, 486DXZ, 486SX
and Pentium™ microprocessors.
The
ICS9131
is driven from a single 32.768 kHz crystal. The
only external components required are the crystal and a 10M
ohm resistor. The device generates the 14.318 MHz system
clock, eliminating the need for a 14.318 MHz crystal. High-
Performance applications may require high speed clock
termination components.
Features
•
•
•
•
•
•
•
•
•
Single 32.768 kHz crystal generates system clock and
selectable CPU clock
Generates CPU clocks from 8 MHz to 100 MHz.
Operates from 3.3V or 5.0V supply
Operates up to 66 MHz at 3.3V
Separate VDD for 32 kHz clock enables it to run from
battery
STOPCLK feature allows for a glitch-free turn-on and
Pen-turn-off of the CPU clock to static processors
Output enable tristates outputs
16-pin PDIP or SOIC package
Frequency selects allow for a smooth transition of
the CPUCLK
Pin Configuration
VDD32 Supply
The
ICS9131
has a separate power supply for the 32.768 kHz
oscillator circuitry. This allows the 32 kHz clock to run from
a battery or other source while the main power to the chip is
disconnected. The VDD32 supply is guaranteed to operate
down to +2.0V, with the clock consuming less than 10µA at
+3.3V and the main VDD at 0V.
The frequencies and power-down options in the
ICS9131
are
mask programmable. Customer specific masks can be made
and prototypes delivered within 6-8 weeks from receipt of
order. ICS also offers standard versions, such as those de-
scribed in this data sheet.
16-Pin DIP or SOIC
Block Diagram
Pentium is a trademark of Intel.
9131 Rev B 052897P
ICS9131
Pin Descriptions
PIN NUMBER
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
PIN NAME
32 kHz
X2
X1
VDD32
VCC
VSS
AGND
OE
FS2
REFCLK
STOPCLK#
VSS
VCC
CPUCLK
FS1
FS0
TYPE
Output
Output
Input
--
--
--
--
Input
Input
Output
Input
--
--
Output
Input
Input
DESCRIPTION
32.768 kHz output.
Connect 32 kHz crystal, this input includes internal load
capacitor for crystal.
Connect 32 kHz crystal, this input includes internal load
capacitor for crystal.
Power Supply for 32 kHz oscillator.
Power Supply.
Ground.
Analog Ground.
OE tristates outputs when low.
CPU clock frequency select 2.
14.318 MHz output.
Stops CPU clock when low.
Ground.
Power supply.
CPU clock output (see Decoding table).
CPU clock frequency select 1.
CPU clock frequency select 0.
Functionality
FS2
0
0
0
0
1
1
1
1
FS1
0
0
1
1
0
0
1
1
FS0
0
1
0
1
0
1
0
1
CPUCLK
16
25
33.3
40
50
60
66.6
80
ACTUALS
16.004
25.059
33.412
40.095
50.119
60.142
66.484
80.190
2
ICS9131
Recommended External Circuit
Notes:
1) The external components shown should be placed as close to the device as possible.
2) Pins 5 and 13 should be connected together externally. One decoupling capacitor may suffice for both pins.
3
ICS9131
Absolute Maximum Ratings
VDD referenced to GND . . . . . . . . . . . . . . . . . . . . . . 7V
Operating temperature under bias. . . . . . . . . . . . . . . . 0°C to +70°C
Storage temperature . . . . . . . . . . . . . . . . . . . . . . . . . . -40°C to +150°C
Voltage on I/O pins referenced to GND. . . . . . . . . . . GND -0.5V to VDD +0.5V
Power dissipation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.5 Watts
Stresses above those listed under Absolute Maximum Ratings may cause permanent damage to the device. This is a stress rating
only and functional operation of the device at these or any other conditions above those indicated in the operational sections
of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect product
reliability.
Electrical Characteristics at 5V
Operating V
DD
= +4.5V to +5.5V; T
A
=0°C to 70°C unless otherwise stated
DC Characteristics
PARAMETER
Input Low Voltage
Input High Voltage
Input Low Current
Input High Current
Pull-up Resistor, Note 1
Output Low Current, Note 1
Output High Current, Note 1
Output Low Voltage
Output High Voltage, Note 1
Supply Current
Output Frequency Change over
Supply and Temperature, Note 1
Standby Supply Current, Note 2
SYMBOL
V
IL
V
IH
I
IL
I
IH
R
pu
I
OL
I
OH
V
OL
V
OH
I
DD
F
d
I
DDSTDBY
TEST CONDITIONS
MIN
-
2.0
-15.0
-2.0
-
25
-
-
2.4
-
-
-
TYP
-
-
-6.0
-
400
45
-53
0.15
3.7
18
0.002
12
MAX
0.8
-
2.0
700
-
-35
0.4
-
35
0.05
25
UNITS
V
V
µA
µA
k ohms
mA
mA
V
V
mA
%
mA
V
IN
=0V
V
IN
=V
DD
V
IN
=V
DD
-1V
V
OUT
=0. 8V
V
OUT
=2.0V
I
OL
=10mA
I
OH
=-30mA
No load, at 50 MHz
With respect to typical
frequency
Unloaded
Note 1: Parameter is guaranteed by design and characterization. Not 100% tested in production.
Note 2: With the STOPCLK pin low (active).
Note 3: Absolute Jitter measured as the shortest and longest period difference to the mean period of the sample set.
4
ICS9131
Electrical Characteristics at 5V
Operating V
DD
= +4.5V to +5.5V; T
A
=0°C to 70°C unless otherwise stated
AC Characteristics
PARAMETER
Output Frequency, Note 1
Input Frequency, Note 1
Output Rise time, Note 1
Rise time, Note 1
Output Fall time, Note 1
Fall time, Note 1
Duty cycle, Note 1
Jitter, 1 sigma from 33-80 MHz,
Note 1
Jitter, Absolute from 33-80 MHz,
Notes 1, 3
Jitter, 1 sigma from 16-25 MHz,
Note 1
Jitter, Absolute from 16-25 MHz,
Note 1, 3
Jitter, 1 sigma from 14 to below,
Note 1
Jitter, Absolute from 14 to below,
Note 1, 3
Frequency Transition time, Note 1
Power-up time, Note 1
SYMBOL
f
o
f
i
t
r
t
r
t
f
t
f
d
t
T
jis
T
jabs
T
jis
T
jabs
T
jis
T
jabs
t
ft
t
pu
TEST CONDITIONS
Clock1
15pF
15pF
15pF
15pF
load,
load,
load,
load,
0.8 to 2.0V
20% to 80% V
DD
2.0 to 0.8V
80% to 20% V
DD
MIN
12.0
2.0
-
-
-
-
45
-
-250
TYP
-
32
0.60
1.6
0.50
0.9
50
50
-
60
MAX
100
38
1.4
3.0
1.2
2.5
55
150
250
150
600
3
5
10.0
15
UNITS
MHz
kHz
ns
ns
ns
ns
%
ps
ps
ps
ps
%
%
ms
ms
15pF load @1.4V
10,000 samples
10,000 samples
10,000 samples
10,000 samples
10,000 samples
10,000 samples
-600
-
-
2.0
3.0
-
1
2
5.0
7.5
Note 1: Parameter is guaranteed by design and characterization. Not 100% tested in production.
Note 2: With the STOPCLK pin low (active).
Note 3: Absolute Jitter measured as the shortest and longest period difference to the mean period of the sample set.
5
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