W133 Datasheet, PDF (2/12 Pages) Cypress Semiconductor – Spread Spectrum System Frequency Synthesizer

PRELIMINARY
W133
Pin Definitions
Pin Name
CPU0:3
Pin No.
41, 42, 45, 46
CPUdiv2_ 0:1
49,50
PCI1:7
PCI_F
9, 11, 12, 14, 15,
17, 18
8
REF0:1
2, 3
IOAPIC0:2
53, 54, 55
48MHz
30
3V66_0:3
21, 22, 25, 26
SEL0:1
32, 33
SEL133/100#
28
X1
5
X2
6
SPREAD#
34
PWRDWN#
35
CPU_STOP#
36
PCI_STOP#
37
VDDQ3
4, 10, 16, 23, 27,
31, 39
VDDQ2
43, 47, 51, 56
GND
1, 7, 13, 19, 20,
24, 29, 38, 40,
44, 48, 52
Pin
Type
O
O
O
O
O
O
O
O
I
I
I
O
I
I
I
I
P
P
G
Pin Description
CPU Clock Outputs 0 through 3: These four CPU clocks run at a frequency set by
SEL133/100#. Output voltage swing is set by the voltage applied to VDDQ2.
Synchronous Memory Reference Clock Output 0 through 1: Reference clock for
Direct RDRAM clock generators running at 1/2 CPU clock frequency. Output voltage
swing is set by the voltage applied to VDDQ2.
PCI Clock Outputs 1 through 7: These seven PCI clock outputs run synchronously
to the CPU clock. Voltage swing is set by the power connection to VDDQ3. PCI1:7
outputs are stopped when PCI _STOP# is held LOW.
PCI_F (PCI Free-running): This PCI clock output runs synchronously to the CPU
clock. Voltage swing is set by the power connection to VDDQ3. PCI_F is not affected
by the state of PCI_STOP#.
14.318-MHz Reference Clock Output: 3.3V copies of the 14.318-MHz reference
clock.
I/O APIC Clock Output: Provides 16.67-MHz fixed frequency. The output voltage
swing is set by the power connection to VDDQ2.
48-MHz Output: Fixed 48-MHz USB output. Output voltage swing is controlled by
voltage applied to VDDQ3.
66-MHz Output 0 through 3: Fixed 66-MHz outputs. Output voltage swing is con-
trolled by voltage applied to VDDQ3.
Mode Select Input 0 through 1: 3.3V LVTTL-compatible input for selecting clock
output modes.
Frequency Selection Input: 3.3V LVTTL-compatible input that selects CPU output
frequency as shown in Table 1.
Crystal Connection or External Reference Frequency Input: Connect to either
a 14.318-MHz crystal or an external reference signal.
Crystal Connection: An output connection for an external 14.318-MHz crystal. If
using an external reference, this pin must be left unconnected.
Active LOW Spread Spectrum Enable: 3.3V LVTTL-compatible input that enables
spread spectrum mode when held LOW.
Active LOW Power Down Input: 3.3V LVTTL-compatible asynchronous input that
requests the device to enter power-down mode.
Active LOW CPU Clock Stop: 3.3V LVTTL-compatible asynchronous input that
stops all CPU and 3V66 clocks when held LOW. CPUdiv2 outputs are unaffected by
this input.
Active LOW PCI Clock Stop: 3.3V LVTTL-compatible asynchronous input that
stops all PCI outputs except PCI_F when held LOW.
Power Connection: Power supply for PCI output buffers, 48-MHz USB output buffer,
Reference output buffers, 3V66 output buffers, core logic, and PLL circuitry. Connect
to 3.3V supply.
Power Connection: Power supply for IOAPIC, CPU, and CPUdiv2 output buffers.
Connect to 2.5V supply.
Ground Connection: Connect all ground pins to the common system ground plane.
Overview
The W133 is designed to provide the essential frequency
sources to work with advanced multiprocessing Intel® archi-
tecture platforms. Split voltage supply signaling provides 2.5V
and 3.3V clock frequencies operating up to 133 MHz.
From a low-cost 14.31818-MHz reference crystal oscillator,
the W133 generates 2.5V clock outputs to support CPUs, core
logic chip set, and Direct RDRAM clock generators. It also pro-
vides skew-controlled PCI and IOAPIC clocks synchronous to
CPU clock, 48-MHz Universal Serial Bus (USB) clock, and rep-
licates the 14.31818-MHz reference clock.
All CPU, PCI, and IOAPIC clocks can be synchronously mod-
ulated for spread spectrum operations. Cypress employs pro-
prietary techniques that provide the maximum EMI reduction
while minimizing the clock skews that could reduce system
timing margins. Spread Spectrum modulation is enabled by
the active LOW control signal SPREAD#.
The W133 also includes power management control inputs. By
using these inputs, system logic can stop CPU and/or PCI
clocks or power down the entire device to conserve system
power.
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