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Cypress Semiconductor Electronic Components Datasheet



W181

Peak Reducing EMI Solution


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W181 pdf
W181
Features
Cypress PREMIS™ family offering
• Generates an EMI optimized clocking signal at the out-
put
• Selectable input to output frequency
• Single 1.25% or 3.75% down or center spread output
• Integrated loop filter components
• Operates with a 3.3V or 5V supply
• Low power CMOS design
• Available in 8-pin SOIC (Small Outline Integrated Cir-
cuit) or 14-pin TSSOP (Thin Shrink Small Outline Pack-
age select options only)
Key Specifications
Supply Voltages: ........................................... VDD = 3.3V±5%
or VDD = 5V±10%
Frequency Range: ............................ 28 MHz Fin 75 MHz
Crystal Reference Range.................. 28 MHz Fin 40 MHz
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.)
Simplified Block Diagram
3.3 or 5.0V
XTAL
Input
40 MHz
Max.
X1
X2
W181
Spread Spectrum
Output
(EMI suppressed)
3.3 or 5.0V
Oscillator or
Reference Input
W181
Spread Spectrum
Output
(EMI suppressed)
Peak Reducing EMI Solution
Table 1. Modulation Width Selection
SS%
0
1
W181-01, 02, 03
Output
Fin Fout Fin
1.25%
Fin Fout Fin
3.75%
W181-51, 52, 53
Output
Fin + 0.625% Fin
– 0.625%
Fin + 1.875% Fin
–1.875%
Table 2. Frequency Range Selection
W181 Option#
FS2 FS1
-01, 51
(MHz)
-02, 52
(MHz)
-03, 53
(MHz)
0 0 28 FIN 38 28 FIN 38
N/A
0 1 38 FIN 48 38 FIN 48
N/A
1 0 46 FIN 60 N/A 46 FIN 60
1 1 58 FIN 75 N/A 58 FIN 75
Pin Configurations
SOIC
CLKIN or X1
NC or X2
GND
SS%
1
2
3
4
8 FS2
7 FS1
6 VDD
5 CLKOUT
CLKIN or X1
NC or X2
GND
SS%
1
2
3
4
8 SSON#
7 FS1
6 VDD
5 CLKOUT
TSSOP
FS2
CLKIN or X1
NC or X2
GND
NC
SS%
NC
1
2
3
4
5
6
7
14 NC
13 NC
12 FS1
11 NC
10 VDD
9 NC
8 CLKOUT
PREMIS is a trademark of Cypress Semiconductor Corporation.
Cypress Semiconductor Corporation • 3901 North First Street • San Jose • CA 95134 • 408-943-2600
July 21, 2000, rev. *B



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W181 pdf
W181
Pin Definitions
Pin Name
CLKOUT
Pin No.
(SOIC)
5
CLKIN or X1
1
Pin No.
(TSSOP)(-01)
8
2
NC or X2
SSON#
FS1:2
2
8(02/03/52/
53)
7, 8 (01/51)
3
--
12, 1
SS%
46
VDD
GND
NC
6 10
34
5, 7, 9, 11, 13,
14
Pin
Type
O
I
I
I
I
I
P
G
NC
Pin Description
Output Modulated Frequency: Frequency modulated copy
of the unmodulated input clock (SSON# asserted).
Crystal Connection or External Reference Frequency In-
put: This pin has dual functions. It may either be connected
to an external crystal, or to an external reference clock.
Crystal Connection: If using an external reference, this pin
must be left unconnected.
Spread Spectrum Control (Active LOW): Asserting this sig-
nal (active LOW) turns the internal modulation waveform on.
This pin has an internal pull-down resistor.
Frequency Selection Bit(s) 1 and 2: These pins select the
frequency range of operation. Refer to Table 2. These pins
have internal pull-up resistors.
Modulation Width Selection: When Spread Spectrum fea-
ture 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 resistor.
Power Connection: Connected to 3.3V or 5V power supply.
Ground Connection: Connect all ground pins to the com-
mon system ground plane.
No Connection.
2



Part Number W181
Description Peak Reducing EMI Solution
Maker Cypress Semiconductor - Cypress Semiconductor
Total Page 9 Pages
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