W254B Datasheet, PDF (2/16 Pages) SpectraLinear Inc – 133MHz Spread Spectrum FTG for Mobile Pentium® III Platforms

W254B
Pin Definitions
Pin Name
CPU
CPU_F
PCI1:6,
PCI_F/FS0,
PCI1/FS1
Pin No.
44, 43
8, 10, 11, 12, 13,
6, 7
APIC
47
SDRAM0:5,
DCLK
3V66_0:1,
3V66_AGP
USB
DOT
REF
VCH_CLK
40, 39, 37, 36,
34, 33, 32
15, 16, 17
21
22
48
19
PWR_DWN#
28
CPU_STP#
30
PCI_STP#
29
SCLK
27
SDATA
26
X1
2
X2
3
VDD_REF,
VDD_PCI,
VDD _3V66,
VDD_48,
VDD_CORE,
VDD_SDRAM,
VDD_SDRAM
VDD_APIC,
VDD_CPU
GND_REF,
GND_PCI,
GND_3V66,
GND_48,
GND_CORE
GND_SDRAM,
GND_SDRAM,
GND_CPU
1, 9, 14, 23, 25,
31, 38
45, 46
4, 5, 18, 20, 24,
35, 41, 42
Pin
Type
O
I/O
O
O
O
O
O
O
O
I
I
I
I
I/O
I
O
P
P
G
Pin Description
CPU Clock Outputs: Frequency is set by the FS0:1 inputs or through serial input
interface. The CPU output is gated by the CLK_STOP# input.
33-MHz PCI Outputs: Except for the PCI_F output, these outputs are gated by
the PCI_STOP# input.
Upon power up, FS0 and FS1 is configured momentarily as input latches allowing
various output frequencies to be selected. See Table 2.
APIC Output: 2.5V fixed 33.3-MHz clock. This output is synchronous to the CPU
clock.
SDRAM Output Clocks: 3.3V outputs running at either 100 MHz or 133 MHz
depending on the setting of FS0:1 inputs. DCLK is a free-running clock.
66-MHz Clock Outputs: 3.3V fixed 66-MHz clock.
USB Clock Output: 3.3V fixed 48-MHz, non-spread spectrum USB clock output.
Dot Clock Output: 3.3V fixed 48-MHz, non-spread spectrum signal.
Reference Clock: 3.3V 14.318-MHz clock output.
Video Control Hub Clock Output: 3.3V selectable 48-MHz non-spread
spectrum or 66.67-MHz spread spectrum clock output.
Power-Down Control: 3.3V LVTTL-compatible input that places the device in
power-down mode when held LOW.
CPU Output Control: 3.3V LVTTL-compatible input that stops only the CPU0
clock. Output remains in the LOW state.
PCI Output Control: 3.3V LVTTL-compatible input that stops PCI1:6 clocks.
Output remains in the LOW state.
SMBus Clock Input: Clock pin for SMBus circuitry.
SMBus Data Input: Data pin for SMBus circuitry.
Crystal Connection or External Reference Frequency Input: This pin has dual
functions. It can be used as an external 14.318-MHz crystal connection or as an
external reference frequency input.
Crystal Connection: Connection for an external 14.318-MHz crystal. If using an
external reference, this pin must be left unconnected.
3.3V Power Connection: Power supply for core logic, PLL circuitry, SDRAM
outputs buffers, PCI output buffers, reference output buffers and 48-MHz output
buffers. Connect to 3.3V.
2.5V Power Connection: Power for APIC and CPU output buffers. Connect to
2.5V.
Ground Connection: Connect all ground pins to the common system ground
plane.
Rev 1.0, November 20, 2006
Page 2 of 16