Integrated
Circuit
Systems, Inc.
General Description
Features
ICS9169C-27
Block Diagram
Frequency Generator for Pentium Based Systems
9169C-27 Rev C 04/16/98
Pin Configuration
The ICS9169C-27 is a low-cost frequency generator
designed specifically for Pentium based chip set systems.
The integrated buffer minimizes skew and provides all the
clocks required. A 14.318 MHz XTAL oscillator provides
the reference clock to generate standard Pentium
frequencies. The CPU clock makes gradual frequency
transitions without violating the PLL timing of internal
microprocessor clock multipliers.
Twelve CPU clock outputs provide sufficient clocks for the
CPU, chip set, memory and up to two DIMM connectors (with
four clocks to each DIMM). Either synchronous(CPU/2) or
asynchronous (32 MHz) PCI bus operation can be selected
by latching data on the BSEL input
32-Pin SOIC/SOJ
Functionality
3.3V10%, 0-70
C
Crystal (X1, X2) = 14.31818 MHz
Pentium is a trademark on Intel Corporation.
Twelve selectable CPU clocks operate up to 83.3MHz
Maximum CPU jitter of 200ps
Six BUS clocks support sync or async bus operation
250ps skew window for CPU outputs, 500ps skew
window for BUS outputs
CPU clocks BUS clocks skew 1-4ns (CPU early)
Integrated buffer outputs drive up to 30pF loads
3.0V - 3.7V supply range, CPU(1:6) outputs 2.5V(2.375-
2.62V) VDD option
32-pin SOIC/SOJ package
Logic inputs latched at Power-On for frequency selection
saving pins as Input/Output
48 MHz clock for USB support and 24 MHz clock for FD.
ADDRESS
SELECT
CPU(1:12)
(MHz)
BUS (1:6)MHz
48MHz
24MHz
REF
FS2
FS1
FS0
BSEL=1
BSEL=0
0
0
0
50
25
32
48
24
REF
0
0
1
60
30
32
48
24
REF
0
1
0
66.6
33.3
32
48
24
REF
0
1
1
REF/2
REF/4
REF/3
REF/2
REF/4
REF
1
0
0
55
27.5
32
48
24
REF
1
0
1
75
37.5
32
48
24
REF
1
1
0
83.3
41.7
32
48
24
REF
1
1
1
Tristate
Tristate
Tristate
Tristate
Tristate
Tristate
VDD Groups:
VDD = X1, X2, REF/BSEL
VDDC1 = CPU1-6
VDDC2 = CPU7-12 & PLL Core
VDDB = BUS1-6
VDDF = 48/24 MHz
Latched Inputs:
L1 = BSEL
L2 = FS0
L3 = FS1
L4 = FS2
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
ICS9169C-27
Pin Descriptions
PIN NUMBER
PIN NAME
TYPE
DESCRIPTION
1
VDD
PWR
Power for device logic.
2
X1
IN
XTAL or external reference frequency input. This input
includes XTAL load capacitance and feedback bias for a
12-16MHz crystal, nominally 14.31818MHz. External crystal
load of 30pF to GND recommended for VDD power on faster
than 2.0ms.
3
X2
OUT
XTAL output which includes XTAL load capacitance.
External crystal load of 10pF to GND recommended for VDD
power on faster than 2.0ms.
4,11,20,26
GND
PWR
Ground for device logic.
5
CPU(1)
OUT
Processor clock output which is a multiple of the input
reference frequency.
FS0
IN
Frequency multiplier select pins. See shared pin description.*
6,7,9,10,15,16,17,18,19
CPU
(2:5) (8:12)
OUT
Processor clock outputs which are a multiple of the input
reference frequency.
8
VDDC1
PWR
Power for CPU(1:6) output buffers only. Can be reduced VDD
for 2.5V (2.375-2.62V) next generation processor clocks.
12
CPU(6)
OUT
Processor clock output which is a multiple of the input
reference frequency internal pull up devices.
FS1
IN
Frequency multiplier select pin. See shared pin description.*
13
CPU(7)
OUT
Processor clock output which is a multiple of the input
reference frequency internal pull up devices.
FS2
IN
Frequency multiplier select pin. See shared pin description.*
14
VDDC2
PWR
Power for CPU PLL, logic and CPU(7:12)output buffers. Must
be nominal 3.3V (3.0 to 3.7V)
21,22,24,25,27,28
BUS (6:1)
OUT
BUS clock outputs which are a multiple of the input
reference clock.
23
VDDB
PWR
Power for BUS clock buffers BUS(1:6).
29
VDDF
PWR
Power for fixed clock buffer (48 MHz, 24 Mhz).
30
24MHz
OUT
Fixed 24MHz clock (assuming a 14.31818MHz REF
frequency).
31
48MHz
OUT
Fixed 48MHz clock (assuming a 14.31818MHz REF
frequency).
32
REF
OUT
Fixed 14.31818MHz clock (assuming a 14.31818MHz REF
frequency).
BSEL
IN
Selection for synchronous or asynchronous bus clock
operation. See shared pin programming description late in this
data sheet for further explanation.*
* Internal pull-up will vary from 350K to 500K based on temperature.
3
ICS9169C-27
The ICS9169C-27 includes a production test verification
mode of operation. This requires that the FS0 and FS1 pins
be programmed to a logic high and the FS2 pin be
programmed to a logic low(see Shared Pin Operation section).
In this mode the device will output the following
frequencies.
Note: REF is the frequency of either the crystal connected
between the devices X1and X2 or, in the case of a device
being driven by an external reference clock, the frequency
of the reference (or test) clock on the devices X1 pin.
Shared Pin Operation - Input/Output Pins 5, 12, 13 and 32
on the ICS9169C-27 serve as dual signal functions to the
device. During initial power-up, they act as input pins. The
logic level (voltage) that is present on these pins at this time
is read and stored into a 4-bit internal data latch. At the end
of Power-On reset, (see AC characteristics for timing values),
the device changes the mode of operation for these pins to
an output function. In this mode the pins produce the
specified buffered clocks to external loads.
To program (load) the internal configuration register for
these pins, a resistor is connected to either the VDD (logic 1)
power supply or the GND (logic 0) voltage potential. A 10
Kilohm(10K) resistor is used to provide both the solid
CMOS programming voltage needed during the power-up
programming period and to provide an insignificant load on
the output clock during the subsequent operating period.
Figs. 1 and 2 show the recommended means of implementing
this function. In Fig. 1 either one of the resistors is loaded
onto the board (selective stuffing) to configure the devices
internal logic. Figs. 2a and b provide a single resistor loading
option where either solder spot tabs or a physical jumper
header may be used.
These figures illustrate the optimal PCB physical layout
options. These configuration resistors are of such a large
ohmic value that they do not effect the low impedance clock
signals. The layouts have been optimized to provide as little
impedance transition to the clock signal as possible, as it
passes through the programming resistor pad(s).
Shared Pin Operation -
Input/Output Pins
Test Mode Operation
Pin
Frequency
REF
REF
48MHz
REF/2
24MHz
REF/4
CPU (1:12)
REF2
BUS (1:6)
BSEL=1
REF/4
BSEL = 0
REF/3
Fig. 1
(Resistors are surface mount devices
shown schematically between 5.m. pads)
*use only one programming resistor
4
ICS9169C-27
Fig. 2a
Fig. 2b
Fig. 3
5
ICS9169C-27
Technical Pin Function Descriptions
VDD
This is the power supply to the internal logic of the device as
well as the following clock output buffers:
A. REF clock output buffers
B. BUS clock output buffers
C. Fixed clock output buffers
This pin may be operated at any voltage between 3.0 and 5.5
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 of these
clocks, please consult the AC parameter table in this data
sheet.
GND
This is the power supply ground return pin for the internal
logic of the device as well as the following clock output
buffers:
A. REF clock output buffers
B. BUS clock output buffers
C. CPU clock output buffers
D. Fixed clock output buffers
X1
This 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 the capacitor.
X2
This 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.
This pin also implements an internal crystal loading capacitor
that is connected to ground. See the data tables for the value
of the capacitor.
CPU
This pin is the clock output that drives processor and other
CPU related circuitry that require clocks which are in tight
skew tolerance with the CPU clock. The voltage swing of
these clocks is controlled by that which is applied to the
VDDC pins of the device. See note on VDDC (1:2). See the
Functionality table at the beginning of this data sheet for a
list of the specific frequencies that this clock operates at and
the selection codes that are necessary to produce these
frequencies.
BUS
This pin is the clock output that is intended to drive the
systems plug-in card bus. The voltage swing of these
clocks is control-led by the supply that is applied to the
VDD pin of the device. See the Functionality table at the
beginning of this data sheet for a list of the specific
frequencies that this clock operates at and the selection
codes that are necessary to produce these frequencies.
FS0, FS1, FS2
These pins control the frequency of the clocks at the CPU,
CPUL, BUS & SDRAM pins. See the Funtionality table at
the beginning of this data sheet for a list of the specific
frequencies that this clock operates at and the selection
codes that are necessary to produce these frequencies. The
device reads these pins at power-up and stores the
programmed selection code in an internal data latch. (See
programming section of this data sheet for configuration
circuitry recommendations.
BSEL
This pin controls whether the BUS clocks will be synchronous
(run at half the frequency) with the CPU and CPUL clocks or
whether they will be asynchronous (run at a pre-programmed
fixed frequency) clock rate. It is a shared pin and is pro
grammed the same way as the frequency select pins.
VDDC (1:2)
These are the power supply pins for the CPU (1:6) and CPU
(7:12) clock buffers. By separating the clock power pins,
each group can receive the appropriate power decoupling
and bypassing necessary to minimize EMI and crosstalk
between the individual signals. VDDC1 can be reduced to
2.5V VDD for advanced processor clocks, which will bring
CPU (1:6) outputs at 0 to 2.5V output swings.
48 MHz
This is a fixed frequency clock that is typically used to drive
Super I/O peripheral device needs.
24 MHz
This is a fixed frequency clock that is typically used to drive
Keyboard controller clock needs.
REF
This is a fixed frequency clock that runs at the same frequency
as the input reference clock (typically 14.31818 MHz) is
and typically used to drive Video and ISA BUS
requirements.
VDDB
This power pin supplies the BUS clock buffers.
VDDF
This power pin supplies the 48/24 MHz clocks.
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