Cypress W167BH Datasheet

PRELIMINARY

133-MHz Spread Spectrum FTG f or Pentium® II Plat f orms

W167B

Cypress Semiconductor Corporation

• 3901 North First Street • San Jose • CA 95134 • 408-943-2600
November 2, 1999

Features

• Maximized EMI Suppression usi ng Cypress’s Spread
Spec t r u m techno logy

• Three copies of CPU outputs select able frequency

• Three copies of 3V66 selectable frequency out put at

3.3V

• T en copies of PCI clocks (select able frequency), 3.3V

• One double strength 14. 318-MHz reference output at

3.3V

• One copy of 48-MHz USB clock

• One copy of selectabl e 24-/48-MHz for SIO

• One copy of CPU- divide-b y-2 output as refer ence input
to Direct Rambus™ Clock Generator ( C ypress W134)

• Three copies of IO APIC

• Av ail able in 48-pin SSOP (300 mils)

Key Specific ati o n s

Supply Voltages:...................................... V

DDQ2

= 2.5V±5%

V

DDQ3

= 3.3V±5%

CPU, CPUdiv2 Output Jitter:............ .. .........................250 ps

CPU, CPUdiv2 Outp ut Skew:................... ................ ... 175 ps

IOAPIC, 3V66 Output Skew: . ...................................... 250 ps

PCI0:8 Pin to Pin Ske w:................... .. ............. .. .. ........500 ps

Duty Cyc l e: ...... ................... ... .. .......... .. ... ......... ... .. ..... 45/5 5 %

Spread Spectrum Modulation:................................... ±0.25%

CPU to 3V66 Output Offset:............ .0.0–1.5 ns (CPU leads)

3V66 to PCI Output Offset:.............. 1.5–4.0 ns (3V66 leads)

CPU to IOAPIC Output Offset:.........1.5–4.0 ns (CPU leads)

Direct Rambus is a trademark of Rambus, Inc. Pentium is a registered trademark of Intel Corporation.

T able 1. Pin Selectable Frequency

SEL133/

100# SEL2 SEL1 SEL0

CPU
MHz

3V66

MHz

PCI

MHz

IOAPIC

MHz

1 1 1 1 133.3 66.7 33.3 16.7
1 1 1 0 138 69 34.5 17.3
1 1 0 1 143 71.5 35.8 17.9
1 1 0 0 148 74 37 18.5
1 0 1 1 150 75 37.5 18.8
1 0 1 0 152.5 76.3 38.1 19.1
1 0 0 1 155 77.5 38.8 19.4
1 0 0 0 160 80 40 20
0 1 1 1 100.2 66.8 33.4 16.7
0 1 1 0 105 70 35 17.5
0 1 0 1 114 76 38 19
0 1 0 0 120 80 40 20
0 0 1 1 66.8 66.8 33.4 16.7
0 0 1 0 124 82.7 41.3 20.7
0 0 0 1 128.5 64.3 32.1 16.1
0 0 0 0 133.9 67 33.5 16.7

Block Diagram

Pin Configuration

Note:

1. Internal 250-kΩ pull-up resistors present on inputs marked with *.
Design should not rely solely on internal pull-up resistor to set I/O
pins HIGH.

[1]

REF2X

CPU_[0:2]

CPUdiv2

3V66_[0:2]

XTA L

PLL 1

X2

X1

PCI_[2:9]

IOAPIC[0:2]

48MHz/SEL0*

PLL2

OSC

÷2

Power

÷2/÷1.5

Down

Logic

÷2

÷2

3

3

PWRDWN#

3

÷2

SIO/24_48#MHz

Serial

Logic

SEL133/100#

SCLK

SDATA

PCI0/SEL2*

PCI1/SEL1*

8

IOAPIC2

REF2X

VDDQ3

X1
X2

GND
SEL2*/PCI0
SEL1*/PCI1

VDDQ3

PCI2

PCI3

PCI4

PCI5

GND

PCI6

PCI7

VDDQ3

PCI8

PCI9

GND

3V66_0
3V66_1
3V66_2
VDDQ3

W167B

GND
VDDQ2
IOAPIC0

GND
VDDQ2

CPUdiv2
GND
VDDQ2
CPU2
GND
VDDQ2
CPU1
CPU0

SDATA
VDDQ3
GND
PWRDN#*
SCLK
VDDQ3

SIO/24_48#MHz

*

48MHz/SEL0*

GND

SEL133/100#

48
47
46
45
44
43
42
41
40
39
38
37
36
35
34
33
32
31
30
29
28
27
26
25

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24

IOAPIC1

Q#

VDDQ3

VDDQ2

VDDQ3

VDDQ2

VDDQ3

W167B

PRELIMINARY

2

Pin Definitions

Pin Name

Pin
No.

Pin

Type Pin Description

CPU0:2 35, 36, 39 O

CPU Clock Outputs 0 through 2:

CPU clock outputs. Their output voltage

swing is controlled by voltage applied to VDDQ2.

SEL133/100# 25 I

SEL133/100#:

Frequen cy selection input pin as shown in Table 1.

PCI0/SEL2 7 I/O

PCI Clock Output 0 and Selection Bit 2:

As an output, this pin works in
conjunctio n wit h PCI2:9. When an input, this pin functions as part of the fre­quency selecti on address (see Table 1).

PCI1/SEL1 8 I/O

PCI Clock Output 1 and Selection Bit 1:

As an output, this pin works in
conjunctio n wit h PCI2:9. When an input, this pin functions as part of the fre­quency selecti on address (see Table 1).

PCI2:9 10, 11, 12,

13, 15, 16,

18, 19

O

PCI Clock Outputs 2 t hrough 9 :

Output vol tage swi ng is cont rolled b y volt age

applied to VDDQ3.

3V66_0:2 21, 22, 23 O

66-MHz Clock Outputs 0 through 2:

Output voltage s wing is controlled by

voltage app li ed to VDDQ3.

CPUdiv2 42 O

CPU-Divide-By-2 Output:

This serves as a reference input signal for Direct

Rambus

Clock Generator (Cypress W134). The output voltage is determined

by VDDQ2.

IOAPIC0:2 46, 45, 1 O

I/O APIC Clock Output 0 through 2:

Provide outputs synchronous to CPU

clock. See Table 1 and Table 5 for their relat ion to other system cloc k outputs.

48MHZ/SEL0 27 I/O

48-MHz Output and Selection Bit 0:

Fixed clock output that defaults to
48-MHz f ollo win g de vi ce po wer -up . When an i nput , t his pin f unc tions as pa rt of
the frequency sel ection address (see Table 1).

SIO/24_48#MHz 28 I/O

Super I/O Referen ce Clock Out put and SIO Clo ck Frequenc y Select:

Fixed
clock outpu t that pr ovi des the reference input clock to a Super I/O de vi ce. The
output freque ncy is det ermined by t he input valu e on this pi n during po wer up .
If input is sampled HIGH, the output operat es at 24 MHz, otherwise, the output
operates at 48 MHz.

REF2X 2 O

Fixed 14.318-MHz Output:

With double strength driving capability.

PWRDWN# 31 I

Power Down Control

X1 4 I

Crystal Connection or External Reference Frequency Input:

This pin has
dual functions . It can b e used as an e xternal 14.318 -MHz crystal conn ection or
as an external reference frequency input.

X2 5 I

Crystal Connection:

An input con necti on f or an ext ernal 14 .31 8-MHz crysta l.

If using an ex ternal reference, this pin must be left unconnected.

SDATA 34 I/O

Serial Data Input:

Data input for Serial Data Interface. Refer to Serial Data

Interface s ec ti o n tha t follo w s.

SCLK 30 I

Serial Clock Input:

Clock input for Serial Data Interface. Refer to Serial Data

Interface s ec ti o n tha t follo w s.

VDDQ2 37, 40, 43, 47 P

Power Connection:

Connected to 2.5V power supply.

VDDQ3 3, 9, 17, 24,

29, 33

P

Power Connection:

Connected to 3.3V supply.

GND 6, 14, 2 0, 26,

32, 38, 41,

44, 48

G

Ground Connecti on:

Connect all ground pins to the common system ground

plane.

W167B

PRELIMINARY

3

Overview

The W167B, a motherboard clock synthesizer, provides 2.5V
CPU clock outputs for advanced CPU and a CPU-divide-by-2
refere nce frequency for Di rect Rambus

Clock Generat or (such
as Cypress W134) i nterf ace. Fix ed ou tput frequenci es are pro­vided for other system functions.

I/O Pin Operation

Pins 7, 8, 27, and 28 are dual-purpose l/O pins. Upon power­up these pins act as log ic in puts, all owing the det erminatio n of
assigned device functions. A short time after power -up, the
logic state of these pins is latched and the pins then become
clock outputs. This feature reduces device pin count by com­bining cloc k outputs with input selec t pi ns.

An external 10-kΩ “strapping” resistor is connected between
each l/O pin and ground or V

DD3

. Connection to gr ound s ets a

latch to “0”, connection to V

DD3

sets a latch to “1”. Figure 1 and
Figure 2 show two suggested methods for strapping resistor
connection.

Upon W167B power up, the first 2 ms of operation is used for
input logic selection. During this period, these dual-purpose
I/O pins ar e three-s tated, all owing the output st rapping resi stor

on each l/O pin to pull the pin and its associated capacitive
clock load to either a logic HIGH or LOW state. At the end of
the 2-ms period, the establi shed logic 0 or 1 condition of each
l/O pin is then latched. Next, the output buffers are enabled,
converting the l/O pins into ope rating clock outputs. The 2-ms
timer starts when V

DD

reaches 2.0V. The input bits can only

be reset by turning V

DD

off and then back on again.

It should be noted that the strapping resistors have no signifi­cant effect on clock output signal integrity. The drive imped­ance of the c lock out puts is <40 Ω (nominal) which is minimally
affected by the 10-kΩ strap to ground or V

DD

. As with the se­ries termination resistor, the output strapping resistor should
be placed as close to the l/O pin as possible in order to keep
the interconnecting trace short. The trace from the resistor to
ground or V

DD

should be ke pt less t han tw o i nches i n lengt h to

prevent system noise coupling during input logic sampling.
When the clock out puts are enabled following the 2-ms input

period, target ( normal) output f requenc y is deliv ered a ssuming
that V

DD

has stabilized. If VDD has not yet reached full value,
output frequency in iti ally ma y be below t arget b ut wil l in crease
to target once V

DD

voltage has stabilized. In either case, a
short output clock cycle may be produced from the CPU clock
outputs when the outputs are enabled.

Power-on
Reset
Timer

Output Three-state

Data

Latch

Hold

QD

W167B

V

DD

Clock Load

R

10 k

Ω

Output
Buffer

(Load O ption 1)

10 k

Ω

(Load O ption 0)

Output
Low

Output Strapping Resistor

Series Termination Resistor

Figure 1. Input Logic Selection Through Resistor Load Option

Power-on
Reset
Timer

Output Three-state

Data

Latch

Hold

QD

W167B

V

DD

Clock Load

R

10 k

Ω

Output
Buffer

Output
Low

Output Strapping Resistor

Series Termination Resistor

Jumper Options

Figure 2. Input Logic Selection Through Jumper Option

W167B

PRELIMINARY

4

CPU/PCI Freq uency Selection

CPU frequency is selected wi th I/O pins 7, 8, 27, (SEL 2/PCI 0,
SEL1/PCI1, 48MHz/SEL0, respectively) and input pin 25
(SEL133/100#). Refer to Table 1 for CPU/PCI frequency pro-
gramming information. Additional frequency selections are
ava il able through th e seri al data interface. Refer to Table 5 on
page 9.

Output Buffer Configuration

Clock Output s

All clock outputs are designed to drive serial terminated clock
lines. The W167B outputs are CMOS-type which provide rail­to-rail output swing.

Crystal Oscillator

The W167B requires one input reference clock to synthesize
all output frequencies. The reference clock can be either an
externally gener ated cloc k signal or the cloc k generat ed by the
internal crystal oscil lator. When using an e x ternal clo c k sig nal,
pin X1 is used as the clock in put and pin X2 is left open.

The internal crystal oscillator is used in conjunction with a
quartz crystal connected t o de vi ce pins X 1 and X2 . Th is f orms
a parallel resonant crystal oscil lator circuit. The W167B incor­porates the necessary feedback resistor and crystal load ca­pacitors. Including typical stray circuit capacitance, the total
load presented to the crystal is approximately 18 pF. For opti­mum frequency accuracy without the addition of external ca­pacitors, a parallel-resonant mode crystal s pecifying a load o f
18 pF should be used. This will typically yield reference fre­quency accuracies within ±100 ppm.

W167B

PRELIMINARY

5

Spread Sp ectrum Feat u re

The device generates a clock that is frequency modulated in
order to increase the bandwidth that it occu pies. By increas ing
the bandwidth of the fundamental and its harmonics, the am­plitudes of the radiated electromagnetic emissions are re­duced. This effect is depicted in Figure 3.

As shown in Figure 3, a harmonic of a modulated cl ock has a
much low er amplitude th an that of an un modulated si gnal. The
reduction in amplitude is dependent on the harmonic number
and the frequency deviation or spread. The equation for the
reduction is

dB = 6.5 + 9*log

10

(P) + 9*log10(F)

Where P is the perce nta ge of de viati on and F is the frequen cy
in MHz where the reduction is measured.

The output clock is modulated with a waveform depicted in
Figure 4. This waveform, as discussed in “Spread Spect rum
Clock Generation f or the Reducti on of Radiated Emissio ns” by
Bush, Fessler, and Hardin produces the maximum reduction
in the amplitude of radiated electromagnetic emissions. The
deviati on selec ted for this chip i s –0.5% do wnspr ead. Fi gure 4
details the Cypress spr eading pat tern. Cypress does offer op­tions with more spread and greater EMI reduction. Cont act
your local Sales representative for details on these devices .

Spread

Spectrum

Enabled

EMI Reduction

Spread

Spectrum

Non-

Figure 3. Typical Clock and SSFTG Comparison

100%

60%
20%

80%
40%

0%

–20%
–40%
–60%
–80%

–100%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

Time

Frequency Shift

Figure 4. Typica l Modulation Profile

W167B

PRELIMINARY

6

Serial Data Interface

The W167B features a two-pin, serial data interface that can
be used to configure internal register settings that control par­ticular device functions. Upon power-up, the W167B initializes
with default register settings, therefore the use of this serial
data interface is optional. The serial interface is write-only (to
the clock chip) and is the dedicated function of device pins

SDATA and SCLOCK. In motherboard applications, SDATA
and SCLOCK are typically driven by two logic outputs of the
chipset. Clock device register changes are normally made
upon system initialization, if any are required. The interface
can also be used duri ng system oper ation for po wer manage­ment functions. Ta b le 2 summarizes the control functions of
the serial data interface.

Operation

Data is written to the W167B in ten bytes of eight bits each. Byte s are written in the order shown in Table 3.

T able 2. Serial Data Interface Control Functions Summary

Control Function Description Common Application

Clock Output Disable Any individual clock output(s) can be disabled. Di s-

abled outputs ar e actively held LO W.

Unused outputs are di sabled to reduce EMI
and system power. Examples are clock out­puts to unused SDRAM DIMM socket or PCI
slot.

CPU Clock Frequency
Selection

Provides CPU/PCI freque ncy selections. Frequen­cy is changed in a smooth and controlled fashion.

For alternate CPU devi ces, and pow er man­agement options. Smooth frequency transi­tion allows CPU fr equency ch ange un der nor-

mal system operati on.
Output Three-state Puts all clock outputs into a high-impedance state. Production PCB testing.
Test Mode All clock outputs toggle in relation with X1 input ,

internal PLL is bypassed. Refer to Tabl e 4.

Production PCB testing.

(Reserved) Reserved function for future device revision or pro-

duc tion device testing.

No user application . Regist er bit must be wri t-

ten as 0.

Table 3. Byte Writing Sequence

Byte Sequence Byte Name Bit Sequence Byte Description

1 Slave Address 11010010 Commands the W167B to acce pt the bi ts i n Data Byte s 0–6 f or internal

register configuration. Since other devices may exist on the s am e com ­mon serial data b us, i t is neces sary to ha ve a sp eci fic s lav e address for
each potential receiver. The slave receiver address f or the W167B is

11010010. Register sett ing will not be made if t he Slav e Address is not
correct (or is f or an alternate slave receiver).

2 Command

Code

Don’t Care Unused by the W167B, th erefore b it values ar e ignored (d on’t care). This

byte must be included in the data write seq uence to mai ntain proper b yte
allocation. The Command Code Byte is part of the st and ard serial com­munication protocol and may be used when writing to another ad­dressed slave receiver on the serial data bus.

3 Byte Count Don’t Care Unused by the W167B, th erefore b it valu es are ignored (d on’t care). This

byte must be included in the data write seq uence to mai ntain proper b yte
allocation. The Byte Count Byte is part of the standard serial communi­cation protocol and may be used when writing to another addressed
slave receiver on the serial dat a bus.

4 Data Byte 0 Refer to Table 4 The data bits in these bytes set internal W167B registers that control

device operation. The data bits are only accepted when the Address
Byte bit sequence is 11010010, as noted above. For description of bit
control functions, refer to Table 4, Data Byte Serial Configuration Map.

5 Data Byte 1
6 Data Byte 2
7 Data Byte 3
8 Data Byte 4
9 Data Byte 5

10 Data Byte 6