Cypress W48C101-01H Datasheet

PRELIMINARY

Spread Spectrum BX System Frequency Generator

W48C101-01

Cypress Semiconductor Corporation

• 3901 North First Street • San Jose • CA 95134 • 408-943-2600
October 7, 1999, rev. **

Features

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

• Four copies of CPU output

• Eight copies of PCI output (Synchronous w/CPU
output)

• T wo copies of 14.318-MHz IO APIC output

• T wo copies of 48-MHz USB output

• Three buffered copies of 14.318-MHz reference input

• Input is a 14.318-MHz XTAL or reference signal

• Selectable 100- M Hz or 66-MHz CPU outputs

• Power man agem ent control input pins

• T est mode and output three-state capability

Key Specific ati o n s

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

DDQ3

= 3.3V±5%

V

DDQ2

= 2.5V±5%

CPU0:3 Jitter (Cycl e to Cycle):................................... 200 ps

CPU0: 3 C lo ck Skew: .................... .. .................... .. ... .... 1 7 5 ps

PCI_ F, PCI1:7 Cl o ck Skew: ..... ... ......... ... .. .......... .. ... ....500 ps

CPU to PCI Clock Skew: ....... .. .....1.5 to 4.0 ns (CPU L e ad s )

Logic inpu ts have 250-kΩ pull-up resistors e xcept SEL100/66 #.

T able 1. Pin Selectable Frequency

SEL

100/66# SEL1 SEL0

CPU

(MHz)

PCI

(MHz) SPREAD#=0

0 0 0 HI-Z HI-Z Don’t Care
0 0 1 66.6 33.3 ±0.9% Center
0 1 0 66.6 33.3 –1% Down
0 1 1 66.6 33.3 –0.5% Down
1 0 0 X1/2 X1/6 Don’t Care
1 0 1 100 33.3 ±0.9% Center
1 1 0 100 33.3 –1% Down
1 1 1 100 33.3 –0.5% Down

Pin ConfigurationBlock Diagram

REF0
REF1

GND

X1
X2

GND

PCI_F

PCI1

VDDQ3

PCI2
PCI3
GND
PCI4
PCI5

VDDQ3

PCI6
PCI7
GND

VDDQ3

GND

VDDQ3

48MHz
48MHz

GND

VDDQ3
REF2
VDDQ2
APIC0
APIC1
GND
NC
VDDQ2
CPU0
CPU1
GND
VDDQ2
CPU2
CPU3
GND
VDDQ3
GND
PCI_STOP#
CPU_STOP#
PWR_DWN#
SPREAD#
SEL0
SEL1
SEL100/66#

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

VDDQ3
REF0

VDDQ2
APIC0

CPU0
CPU1

CPU2
CPU3

PCI_F

XTAL

PLL Ref Freq

PLL 1

SEL100/66#

X2

X1

REF1

VDDQ3

Stop

Clock

Control

Stop

Clock

Control

PCI1

PWR_DWN#

Power
Down
Control

PCI2
PCI3

PCI4
PCI5

48MHz
48MHz

PLL2

÷2/÷3

OSC

REF2

VDDQ2

PCI_STOP#

CPU_STOP#

PCI6
PCI7

VDDQ3

APIC1

SEL0
SEL1

SPREAD#

W48C101-01

PRELIMINARY

2

Pin Definitions

Pin Name

Pin
No.

Pin

Type Pin Description

CPU0:3 40, 39, 36,

35

O

CPU Clock Output s 0 through 3:

These four CPU clock outputs are controlled b y
the CPU_STO P# contr ol pin . Output vol tage swing is cont roll ed by v oltag e appli ed
to VDDQ2.

PCI1:7 8, 10, 11, 13,

14, 16, 17

O

PCI Bus Clock Outputs 1 thr ough 7:

These sev en PCI clock outputs are cont rolled
by the PCI _STOP# con trol pin. Out put volt age swing is controlle d by v oltage applie d
to VDDQ3.

PCI_F 7 O

Fixed PCI Clock Output:

Unlike PCI 1:7 outputs , this output i s not cont rolled by the
PCI_STOP# control pin. Output voltage swing is controlled by voltage applied to
VDDQ3.

CPU_STOP# 30 I

CPU_STOP# Input :

When brought LO W, c lock output s CPU0: 3 are s topped LO W
after completing a full clock cycle (2–3 CPU clock latency). When brought HIGH,
clock out puts CPU0:3 start beginn ing with a full clock cyc le (2–3 CPU clock latency).

PCI_STOP# 31 I

PCI_STOP# I nput:

The PCI_STOP# input enables the PCI 1:7 out puts when HIGH
and causes them to remai n at l ogic 0 when LO W. The PCI_STOP signal i s latc hed
on the rising edge of PCI_F. Its effects take place on the next PCI_F clock cycle.

SPREAD# 28 I

SPREAD# Input:

When brough t LOW t his pin activ ates Spread Spectrum cloc king.

APIC0:1 45, 44 O

I/O APIC Clock Outputs:

Provides 14.31 8-MHz fi xed frequency. The output volt-

age swing is controlled by VDDQ2.

48MHz 22, 23 O

48-MHz Output s:

Fixed c lock output s at 48 MHz. Output vol tage swin g is controll ed

by volt age applied to VDDQ3.

REF0:2 1, 2, 47 O

Fixed 14.318-MHz Outp uts 0 through 2:

Used for various system applications.

Output voltage swing is contro ll ed by voltage appl ied to VDDQ3.

SEL100/66#
SEL1:0

25, 26, 27 I

Frequency Selection Input:

Selects power-up default CPU clock frequency as

shown in Table 1 on page 1.

X1 4 I

Crystal Connection or Exte rnal Ref erence Freq uenc y Input:

Connect to either

a 14.318-MHz crystal or reference signal .

X2 5 I

Crystal Connection:

An input connection for an external 14.318-MHz crystal. If

using an external reference, this pin must be left unconnected.

PWR_DWN# 29 I

Power Down Control:

When this input is LOW , device goes into a lo w-power con­dition. All outputs are held LOW while in power-down. CPU and PCI clock outputs
are stopped LO W a fter co mpleti ng a ful l cl oc k cy cl e (2–3 CPU clock cyc le latency) .
When brought HIGH, CPU , SDRAM and PCI outputs start with a full cloc k cy cle at
full operating frequency (3 ms maximum lat ency).

VDDQ3 9, 15, 19, 21,

33, 48

P

Power Connection:

Connect to 3.3V supply.

VDDQ2 37,41,46 P

Power Connect ion:

Po wer supply for CPU0:3 and APIC0:1 output buff ers. Connect

to 2.5V suppl y.

GND 3, 6, 12, 18,

20, 24, 32,

34, 38, 43

G

Ground Connection:

Connect all ground pins to the common system ground

plane.

NC 42 -

No Connect:

Do not connect.

W48C101-01

PRELIMINARY

3

Spread Sp ectrum Clockin g

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 1.

As shown in Figure 1, a harmonic of a modulated clock 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 2. This waveform, as discussed in “Spread Spectrum
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
deviation selected for this chip is –0.5%, –1.0%, or ±0.9% of
the selected frequency. Figure 2 detail s the Cypre ss spr eading
pattern. Cypress does offer options with more spread and
greater EMI r eduction. Cont act your local Sal es represe ntativ e
for details on these devices .

Spread Spectrum clocking is activated or deactivated by se­lecting the appropriate values for SPREAD#.

Figure 1. Clock Harmonic with and without SSCG Modulation Frequency Domain Representation

∆

SSC

non-SSC

Highest peak

δ of f

nom

f

nom

MAX (+0.5%)

MIN (–0.5%)

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

FREQUENCY

Figure 2. Typica l Modulation Profile