Integrated
Circuit
Systems, Inc.
General Description
Features
ICS9148-25
Block Diagram
Pentium/Pro
TM
System and CyrixTM Clock Chip
9148-25 Rev B 5/20/99
Pin Configuration
48-Pin SSOP
Pentium is a trademark on Intel Corporation.
Generates system clocks for CPU, IOAPIC, SDRAM,
PCI, plus 14.318 MHz ), USB, Plus Super I/O
Spread spectrum for CPU/SDRAM/PCI clocks default
Supports single or dual processor systems
Modulation of Spread Spectrum selectable as 0.5, 1.0,
2.0 or none
Supports Intel 60, 66.8MHz, Cyrix 55, 75MHz plus 83.3
and 68MHz (Turbo of 66.6) speeds.
Synchronous clocks skew matched to 250ps window on
CPU, SDRAM and 500ps window on PCI clocks
CPU clocks to PCI clocks skew 1-4ns (CPU early)
MODE input pin selects optional power management
input control pins
Two fixed outputs, 48MHz and 24 MHz
Separate 2.5V and 3.3V supply pins
- 2.5V or 3.3V output: CPU, IOAPIC (Strength
selectable)
- 3.3V outputs: SDRAM, PCI, REF, 48/24 MHz
No power supply sequence requirements
48 pin 300 mil SSOP
The ICS9148-25 is a Clock Synthesizer chip for Pentium and
PentiumPro plus Cyrix CPU based Desktop/Notebook systems
that will provide all necessary clock timing.
Features include four CPU, seven PCI and eight SDRAM
clocks. Two reference outputs are available equal to the crystal
frequency, plus the IOAPIC output powered by VDDL.
Additionally, the device meets the Pentium power-up
stabilization, which requires that CPU and PCI clocks be stable
within 2ms after power-up.
High drive PCICLK and SDRAM outputs typically provide
greater than 1 V/ns slew rate into 30pF loads. CPUCLK outputs
typically provide better than 1V/ns slew rate into 20pF loads
while maintaining 50 5% duty cycle. The REF clock outputs
typically provide better than 0.5V/ns slew rates.
The ICS9148-25 accepts a 14.318MHz reference crystal or
clock as its input and runs on a 3.3V supply.
Sperad Spectrum is modulated in center-spread mode on CPU/
SDRAM/PCI clocks. Modulation amount is selectable at
power-up (latched inputs) for 0.5, 1.0, 2.0 or No spreading.
Power Groups
VDD = Supply for PLL core.
VDD1 = REF (0:2), X1, X2
VDD2 = PCICLK_F, PCICLK (0:5)
VDD3 = SDRAM (0:5), SDRAM6/CPU_STOP#,
SDRAM7/PCI_STOP#
VDD4 = 48MHz, 24MHz
VDDL1 = IOAPIC
VDDL2 = CPUCLK (0:3)
ICS reserves the right to make changes in the device data identified in this
publication without further notice. ICS advises its customers to obtain the latest
version of all device data to verify that any information being relied upon by the
customer is current and accurate.
2
ICS9148-25
Pin Descriptions
Functionality
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*Internal pull-up resistor of 120 to 150K to 3.3V on indicated inputs.
V
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= 3.3V 5% V
DDL
= 2.5V 5% or 3.3V 5%, T
A
= 0 to 70C
Crystal (X1, X2) = 14.31818 MHz
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ICS9148-25
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Mode Pin - Power Management Input Control
Power Management Functionality
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Spread Spectrum Functionality
CPU 3.3_2.5V Buffer selector for CPUCLK and IOAPIC drivers.
#
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*default with internal pull-ups
4
ICS9148-25
Technical Pin Function Descriptions
VDD(1,2,3,4)
This is the power supply to the internal core logic of the
device as well as the clock output buffers for REF(0:1),
PCICLK, 48/24MHzA/B and SDRAM(0:7).
This pin operates at 3.3V volts. Clocks from the listed buffers
that it supplies will have a voltage swing from Ground to this
level. For the actual guaranteed high and low voltage levels
for the Clocks, please consult the DC parameter table in this
data sheet.
VDDL1,2
This is the power supplies for the CPUCLK and IOAPCI
output buffers. The voltage level for these outputs may be
2.5 or 3.3volts. Clocks from the buffers that each supplies will
have a voltage swing from Ground to this level. For the actual
Guaranteed high and low voltage levels of these Clocks,
please consult the DC parameter table in this Data Sheet. See
control pin CPUCLK3.3_2.5# for output buffer strength
matching VDDL required for skew control.
GND
This is the power supply ground (common or negative) return
pin for the internal core logic and all the output buffers.
X1
This input pin serves one of two functions. When the device
is used with a Crystal, X1 acts as the input pin for the
reference signal that comes from the discrete crystal. When
the device is driven by an external clock signal, X1 is the
device input pin for that reference clock. This pin also
implements an internal Crystal loading capacitor that is
connected to ground. See the data tables for the value of this
capacitor. Also includes feedback resistor from X2.
X2
This Output pin is used only when the device uses a Crystal
as the reference frequency source. In this mode of operation,
X2 is an output signal that drives (or excites) the discrete
Crystal. The X2 pin will also implement an internal Crystal
loading capacitor that is connected to ground. See the Data
Sheet for the value of this capacitor.
CPUCLK (0:3)
These Output pins are the Clock Outputs that drive processor
and other CPU related circuitry that requires clocks which are
in tight skew tolerance with the CPU clock. The voltage
swing of these Clocks are controlled by the Voltage level
applied to the VDDL2 pin of the device. See the Functionality
Table for a list of the specific frequencies that are available
for these Clocks and the selection codes to produce them.
See control pin CPUCLK3.3_2.5# for output buffer strength
matching VDDL required for CPU to SDRAM skew control.
These clocks are modulated by Sperad Spectrum.
SDRAM(0:7)
These Output Clocks are use to drive Dynamic RAM's and
are low skew copies of the CPU Clocks. The voltage swing of
the SDRAM's output is controlled by the supply voltage
that is applied to VDD3 of the device, operates at 3.3 volts.
These clocks are modulated by Sperad Spectrum.
48MHz
This is a fixed frequency Clock output at 48MHz that is
typically used to drive USB devices.
24MHz
This pin is a fixed frequency clock output typically used to
drive Super I/O devices.
IOAPIC
This Output is a fixed frequency Output Clock that runs at
the Reference Input (typically 14.31818MHz) . Its voltage
level swing is controlled by VDDL1 and may operate at 2.5 or
3.3volts.
REF(0:2)
The REF Outputs are fixed frequency Clocks that run at the
same frequency as the Input Reference Clock X1 or the
Crystal (typically 14.31818MHz) attached across X1 and X2.
PCICLK_F
This Output is equal to PCICLK(0:5) and is FREE RUNNING,
and will not be stopped by PCI_STP#. This clock is modulated
by Spread Spectrum.
PCICLK (0:5)
These Output Clocks generate all the PCI timing requirements
for a Pentium/Pro based system. They conform to the current
PCI specification. They run at 1/2 CPU frequency, or CPU/2.5,
see frequency table. These clocks are modulated by Sperad
Spectrum.
FS (0,1,2)
These Input pins control the frequency of the Clocks at the
CPU, PCICLK and SDRAM output pins. See frequency table.
These pins are all Full-time inputs with a pull-up to VDD.
MODE
This Input pin is used to select the Input function of the
Power Management I/O pins 26 and 27. An active Low will
place pins in the Input mode and enable those stop clock
functions. This pin is a full-time input with a pull-up to VDD.
5
ICS9148-25
CPU3.3_2.5#
This Input pin controls the CPU and IOAPIC output buffer
strength for skew matching CPU and SDRAM outputs to
compensate for the external VDDL supply condition. It is
important to use this function when selecting power supply
requirements for VDDL1,2. A logic "0" (ground) will indicate
2.5V operation and a logic "1" will indicate 3.3V operation.
This pin has an internal pull-up to VDD. This pin is a latched
input.
PD#
This is an asynchronous active Low Input pin used to Power
Down the device into a Low Power state by not removing the
power supply. The internal Clocks are disabled and the VCO
and Crystal are stopped. Powered Down will also place all the
Outputs in a low state at the end of their current cycle. The
latency of Power Down will not be greater than 3ms. This pin
is a Full-time input with a pull-up to VDD.
CPU_STOP#
This is a active Low Input pin used to stop the CPUCLK
clocks in an active low state. All other clocks will continue to
run while this function is enabled. The CPUCLK's will have a
turn OFF latency and a turn ON latency of 2 or 3 CPU clocks.
This pin is a Full-time input with a pull-up to VDD.
PCI_STOP#
This is a synchronous active Low Input pin used to stop the
PCICLK (0:5) clocks in a low state. It will not effect PCICLK_F
or any other outputs. There is only one full PCI clock output
for Turn OFF or Turn ON latency. This pin is a Full-time input
with a pull-up to VDD.
Technical Pin Function Descriptions
SSM (0:1)
These pins define the input condition for the Spread Spectrum
amount of modulation. See Spread Spectrum functionality
table. Note that spreading is only done on the CPU/SDRAM/
PCI clocks no modulation is done on the REF, IOAPIC or
PLL2 (24, 48MHz) outputs.
These latched input pins are defined at power-on for logic Hi
or logic Low condition by external pull-up or pull-down
resistors, or the internal pull-up resistor to VDD. See shared
pin operation of Input/output pins on next page.
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