W184HT [CYPRESS]
Clock Generator, 28MHz, CMOS, PDSO24, 0.209 INCH, MO-150AD, SSOP-24;
| 型号： | W184HT |
| 厂家： | 
CYPRESS |
| 描述： | Clock Generator, 28MHz, CMOS, PDSO24, 0.209 INCH, MO-150AD, SSOP-24 外围集成电路 光电二极管 |
| 文件： | 总8页 (文件大小：131K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
W184
Six Output Peak Reducing EMI Solution
Features
Table 1. Modulation Width Selection
Cypress PREMIS™ family offering
• Generates an EMI optimized clocking signal at the
output
• Selectable input to output frequency
• Six 1.25%, 3.75%, or 0% down or center spread outputs
• One non-Spread reference output
• Integrated loop filter components
• Operates with a 3.3 or 5V supply
•
W184
W184-5
Output
SS%
Output
0
F
F
≥ F ≥ F – 1.25%
F + 0.625% ≥ F ≥ –
in
in
out
in
in
in
0.625%
1
≥ F ≥ F – 3.75%
F + 1.875% ≥ F ≥
–1.875%
out
in
in
in
Table 2. Frequency Range Selection
• Low power CMOS design
• Available in 24-pin SSOP (Shrunk Small Outline
Package)
• Outputs may be selectively disabled
FS2
0
FS1
0
Frequency Range
8 MHz ≤ F ≤ 10 MHz
IN
0
1
10 MHz ≤ F ≤ 15 MHz
IN
Key Specifications
1
0
15 MHz ≤ F ≤ 18 MHz
IN
Supply Voltages: ...........................................V = 3.3V±5%
DD
1
1
18 MHz ≤ F ≤ 28 MHz
IN
or V = 5V±10%
DD
Frequency Range: .............................. 8 MHz ≤ F ≤ 28 MHz
in
Table 3. Output Enable
Crystal Reference Range.................... 8 MHz ≤ F ≤ 28 MHz
in
EN1
EN2
CLK0:4
CLK5
Cycle to Cycle Jitter:........................................ 300 ps (max.)
Selectable Spread Percentage: ....................1.25% or 3.75%
Output Duty Cycle: ............................... 40/60% (worst case)
Output Rise and Fall Time: .................................. 5 ns (max.)
0
0
1
1
0
1
0
1
Low
Low
Low
Active
Low
Active
Active
Active
Simplified Block Diagram
Pin Configuration
3.3 or 5.0V
SSOP
REFOUT
FS2
SSON#
RESET
1
2
3
4
5
6
7
8
9
24
23
22
21
20
19
X1
XTAL
Input
X1
FS1
X2
Spread Spectrum
Outputs
(EMI suppressed)
W184
X2
VDD
VDD
GND
NC
SS%
EN2
GND
18 EN1
CLK5
17
3.3 or 5.0V
VDD
16
CLK0
VDD
CLK1
10
11
CLK4
GND
15
14
CLK2 12
CLK3
13
Oscillator or
Reference Input
Spread Spectrum
W184
Outputs
(EMI suppressed)
PREMIS is a trademark of Cypress Semiconductor Corporation.
Cypress Semiconductor Corporation
•
3901 North First Street
•
San Jose
•
CA 95134
•
408-943-2600
July 25, 2000, rev. *B
W184
Pin Definitions
Pin
Type
Pin Name
Pin No.
Pin Description
CLK0:5
9, 11, 12, 13,
15, 17
O
I
Modulated Frequency Outputs: Frequency modulated copies of the unmod-
ulated input clock (SSON# asserted).
CLKIN or X1
3
Crystal Connection or External Reference Frequency Input: This pin has
dual functions. It may either be connected to an external crystal, or to an
external reference clock.
NC or X2
SS%
4
6
I
I
Crystal Connection: If using an external reference, this pin must be left un-
connected.
Modulation Width Selection: When Spread Spectrum feature is turned on,
this pin is used to select the amount of variation and peak EMI reduction that
is desired on the output signal. This pin has an internal pull-up resistors.
Reset
23
14
I
ModulationProfileRestart: A rising edgeon thisinputrestarts the modulation
pattern at the beginning of its defined path. This pin has an internal pull-down
resistor.
REFOUT
O
Non-Modulated Output: This pin provides a copy of the reference frequency.
This output will not have the Spread Spectrum feature enabled regardless of
the state of logic input SSON#.
EN1:2
18, 7
24
I
I
Output Enable Select Pins: These pins control the activity of specific output
buffers. Set them to disable unused outputs using Table 3 as a guide.
SSON#
Spread Spectrum Control (Active LOW): Asserting this signal (active LOW)
turns the internal modulation waveform on. This pin has an internal pull-down
resistor.
FS1:2
VDD
22, 2
I
Frequency Selection Bit 1 and 2: These pins select the frequency of opera-
tion. Refer to Table 1. These pins have internal pull-up resistors.
10, 16, 20, 21
P
Power Connection: Connected to 3.3V or 5V power supply.
2
W184
times the reference frequency. (Note: For the W184 the output
frequency is nominally equal to the input frequency.) The
unique feature of the Spread Spectrum Frequency Timing
Generator is that a modulating waveform is superimposed at
the input to the VCO. This causes the VCO output to be slowly
swept across a predetermined frequency band.
Overview
The W184 products are one series of devices in the Cypress
PREMIS family. The PREMIS family incorporates the latest
advances in PLL spread spectrum frequency synthesizer tech-
niques. By frequency modulating the output with a low-
frequency carrier, peak EMI is greatly reduced. Use of this
technology allows systems to pass increasingly difficult EMI
testing without resorting to costly shielding or redesign.
Because the modulating frequency is typically 1000 times
slower than the fundamental clock, the spread spectrum pro-
cess has little impact on system performance.
In a system, not only is EMI reduced in the various clock lines,
but also in all signals which are synchronized to the clock.
Therefore, the benefits of using this technology increase with
the number of address and data lines in the system. The Sim-
plified Block Diagram shows a simple implementation.
Frequency Selection With SSFTG
In Spread Spectrum Frequency Timing Generation, EMI re-
duction depends on the shape, modulation percentage, and
frequency of the modulating waveform. While the shape and
frequency of the modulating waveform are fixed for a given
frequency, the modulation percentage may be varied.
Functional Description
Using frequency select bits (FS1:2 pins), the frequency range
can be set. Spreading percentage may be selected to 1.25%
or 3.75% (see Table 1).
The W184 uses a Phase-Locked Loop (PLL) to frequency
modulate an input clock. The result is an output clock whose
frequency is slowly swept over a narrow band near the input
signal. The basic circuit topology is shown in Figure 1. The
input reference signal is divided by Q and fed to the phase
detector. A signal from the VCO is divided by P and fed back
to the phase detector also. The PLL will force the frequency of
the VCO output signal to change until the divided output signal
and the divided reference signal match at the phase detector
input. The output frequency is then equal to the ratio of P/Q
A larger spreading percentage improves EMI reduction. How-
ever, large spread percentages may either exceed system
maximum frequency ratings or lower the average frequency to
a point where performance is affected. For these reasons,
spreading percentage options are provided.
VDD
Clock Input
CLKOUT
Freq.
Divider
Q
Phase
Detector
Charge
Pump
Post
Dividers
Reference Input
(EMI suppressed)
VCO
Σ
Modulating
Waveform
Feedback
Divider
P
PLL
GND
Figure 1. Functional Block Diagram
3
W184
Where P is the percentage of deviation and F is the frequency
in MHz where the reduction is measured.
Spread Spectrum Frequency Timing
Generation
The output clock is modulated with a waveform depicted in
. This waveform, as discussed in “Spread Spectrum
The device generates a clock that is frequency modulated in
order to increase the bandwidth that it occupies. By increasing
the bandwidth of the fundamental and its harmonics, the am-
plitudes of the radiated electromagnetic emissions are re-
Clock Generation for the Reduction of Radiated Emissions” by
Bush, Fessler, and Hardin produces the maximum reduction
in the amplitude of radiated electromagnetic emissions.
details the Cypress spreading pattern. Cypress does offer
options with more spread and greater EMI reduction. Contact
your local Sales representative for details on these devices.
duced. This effect is depicted in
.
As shown in , a harmonic of a modulated clock has a
much lower amplitude than that of an unmodulated signal. 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 (P) + 9*log (F)
10
10
EMI Reduction
SSFTG
Typical Clock
Spread
Spectrum
Enabled
Non-
Spread
Spectrum
Frequency Span (MHz)
Down Spread
Frequency Span (MHz)
Center Spread
Figure 2. Clock Harmonic with and without SSCG Modulation Frequency Domain Representation
MAX.
MIN.
Figure 3. Typical Modulation Profile
4
W184
Absolute Maximum Ratings
Stresses greater than those listed in this table may cause per-
manent damage to the device. These represent a stress rating
above those specified in the operating sections of this specifi-
cation is not implied. Maximum conditions for extended peri-
ods may affect reliability.
only. Operation of the device at these or any other conditions
.
Parameter
Description
Voltage on any pin with respect to GND
Storage Temperature
Rating
–0.5 to +7.0
–65 to +150
–55 to +125
0 to +70
Unit
V
V
, V
DD IN
T
T
°C
°C
°C
W
STG
B
Ambient Temperature under Bias
Operating Temperature
T
A
P
Power Dissipation
0.5
D
: 0°C < T < 70°C, V = 3.3V ±5%
DC Electrical Characteristics
A
DD
Parameter
Description
Supply Current
Test Condition
Min.
Typ.
Max.
Unit
mA
ms
I
18
32
5
DD
ON
t
Power Up Time
First locked clock cycle after Power
Good
V
V
V
V
Input Low Voltage
Input High Voltage
Output Low Voltage
Output High Voltage
Input Low Current
Input High Current
Output Low Current
Output High Current
Input Capacitance
Input Capacitance
Input Pull-Up Resistor
Clock Output Impedance
0.8
0.4
V
V
IL
2.4
IH
V
OL
OH
2.4
V
I
I
I
I
Note 1
Note 1
–50
µA
µA
mA
mA
pF
pF
kΩ
Ω
IL
50
IH
@ 0.4V, V = 3.3V
15
15
OL
OH
DD
@ 2.4V, V = 3.3V
DD
C
C
R
All pins except CLKIN
CLKIN pin only
7
I
6
10
I
500
25
P
Z
OUT
Note:
1. Inputs FS1:2, SS% have a pull-up resistor; Input SSON# has a pull-down resistor.
5
W184
DC Electrical Characteristics: 0°C < T < 70°C, V = 5V ±10%
A
DD
Parameter
Description
Supply Current
Test Condition
Min.
Typ.
Max.
50
Unit
mA
ms
I
t
30
DD
ON
Power Up Time
First locked clock cycle after
Power Good
5
V
V
V
V
Input Low Voltage
Input High Voltage
Output Low Voltage
Output High Voltage
Input Low Current
Input High Current
Output Low Current
Output High Current
Input Capacitance
Input Capacitance
Input Pull-Up Resistor
Clock Output Impedance
0.15V
0.4
V
V
IL
DD
0.7V
IH
DD
V
OL
OH
2.4
V
I
I
I
I
Note 2
Note 2
–50
µA
µA
mA
mA
pF
pF
kΩ
Ω
IL
50
IH
@ 0.4V, V = 5V
24
24
OL
OH
DD
@ 2.4V, V = 5V
DD
C
C
R
All pins except CLKIN
CLKIN pin only
7
I
6
10
I
500
25
P
Z
OUT
AC Electrical Characteristics: T = 0°C to +70°C, V = 3.3V ±5% or 5V±10%
A
DD
Symbol
Parameter
Input Frequency
Test Condition
Min.
Typ.
Max.
Unit
MHz
MHz
ns
f
Input Clock
Spread Off
8
8
28
28
5
IN
f
t
t
t
t
t
Output Frequency
Output Rise Time
Output Fall Time
OUT
R
V
V
, 15-pF load 0.8V–2.4V
2
2
DD
, 15-pF load 2.4V–0.8V
DD
5
ns
F
Output Duty Cycle
Input Duty Cycle
15-pF load
40
40
60
60
300
%
OD
ID
%
Jitter, Cycle-to-Cycle
Harmonic Reduction
250
ps
JCYC
EMI
f
= 40 MHz, third harmonic
8
dB
RED
out
measured, reference board,
15-pF load
t
Output to Output Skew
200
ps
SK
Note:
2. Inputs FS1:2 have a pull-up resistor; Input SSON# has a pull-down resistor.
6
W184
placed as close to the V pin as possible, otherwise the in-
creased trace inductance will negate its decoupling capability.
Application Information
DD
Recommended Circuit Configuration
The 10-µF decoupling capacitor shown should be a tantalum
type. For further EMI protection, the V
made via a ferrite bead, as shown.
connection can be
DD
For optimum performance in system applications the power
supply decoupling scheme shown in Figure 4 should be used.
V
decoupling is important to both reduce phase jitter and
DD
EMI radiation. The 0.1-µF decoupling capacitor should be
R1
Clock Output
Logic Input
1
24
23
22
Logic Input
2
Logic Input
C1
0.1
Logic Input
Reference Input
3
µF
µF
XTAL connection or NC
4
21
20
5
Logic Input
Logic Input
6
7
NC
19
18
17
16
15
14
C1
0.1
Logic Input
8
9
R1
Output
Clock
Clock Output
R1
10
11
12
C1
0.1 µF
R1
R1
Output
Output
Clock
Clock
Clock Output
Clock Output
R1
R1
13
C1
0.1 µF
FB
C2
10-
3.3 or 5V System Supply
µF Tantalum
Figure 4. Recommended Circuit Configuration
Ordering Information
Package
Name
Ordering Code
W184
Package Type
H
24-Pin SSOP (209-mil)
W184-5
Document #: 38-00797-B
7
W184
Package Diagram
24-Pin Shrink Small Outline Package (SSOP, 209 mils)
© Cypress Semiconductor Corporation, 2000. The information contained herein is subject to change without notice. Cypress Semiconductor Corporation assumes no responsibility for the use
of any circuitry other than circuitry embodied in a Cypress Semiconductor product. Nor does it convey or imply any license under patent or other rights. Cypress Semiconductor does not authorize
its products for use as critical components in life-support systems where a malfunction or failure may reasonably be expected to result in significant injury to the user. The inclusion of Cypress
Semiconductor products in life-support systems application implies that the manufacturer assumes all risk of such use and in doing so indemnifies Cypress Semiconductor against all charges.
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