Home >> W155 Search >> Cypress Semiconductor W155 Datasheet

W155 Datasheet

Spread Spectrum Frequency Timing Generator

No Preview Available !

W155 pdf
W155
Spread Spectrum Frequency Timing Generator
Features
• Generates a spread spectrum timing signal (SYSCLK)
and a non-spread signal (USBCLK)
• Requires a 14.318-MHz crystal for operation
• Supports MIPS microprocessor clock frequencies
• Reduces peak EMI by as much as 12 dB
• Integrated loop filter components
• Cycle-to-cycle jitter = 250 ps (max)
• Operates with a 3.3 or 5.0V power supply
• Spread output is selectable from 10 to 133 MHz
• TEST mode supports modulation off (High-Z) and spe-
cial test input reference frequency
• Guaranteed 45/55 duty cycle
• Packaged in a 16-pin, 300-mil-wide SOIC (Small Outline
Integrated Circuit)
Overview
The W155 incorporates the latest advances in PLL-based
spread spectrum frequency synthesizer technology. By fre-
quency modulating the SYSCLK output with a low-frequency
carrier, peak EMI can be greatly reduced in a system. Use of
this technique allows systems to pass increasingly difficult EMI
testing without resorting to costly shielding or redesign.
In a system that uses the W155, not only is EMI reduced in the
various clock lines, but also in all signals which are synchro-
nized to SYSCLK. Therefore, the benefits of using this tech-
nique increase with the number of address and data lines in
the system.
The W155 is specifically targeted toward MIPS microproces-
sor based systems where EMI is of particular concern. Each
device uses a single 14.318-MHz crystal to generate a select-
able spread spectrum output and an unmodulated 48-MHz
USB Output.
The spreading function can be disabled by taking the SSON#
pin high. Spread percentage can be selected with the SS%
input (see Table 2 below).
Table 1. Frequency Selection (14.318-MHz Reference)
SYSCLK
FS3 FS2 FS1 FS0 (Output Freq.)
0 0 0 0 133.3 MHz
0001
120 MHz
0010
100 MHz
0 0 1 1 74.77 MHz
0100
70 MHz
0101
66.6 MHz
0110
60 MHz
0111
50 MHz
1000
40 MHz
1 0 0 1 33.33 MHz
1010
30 MHz
1011
25 MHz
1100
20 MHz
1 1 0 1 16.67 MHz
1110
12 MHz
1111
10 MHz
Table 2. Spread Percentage Selection
SS%
0
1
Spread Percentage
–1.25%
–3.75%
[1]
Pin Configuration
VDD
X1
X2
GND
FS3*
VDD
FS2*
FS1*
1
2
3
4
5
6
7
8
16 TEST
15 VDD
14 USBCLK/SS%*
13 GND
12 SYSCLK
11 GND
10 FS0*
9 SSON#^
Note:
1. Internal pull-up resistor present on inputs marked with ‘*’ and pull-down
resistor present on input marked with ‘^’.
Cypress Semiconductor Corporation • 3901 North First Street • San Jose • CA 95134 • 408-943-2600
September 29, 1999, rev. **
Cypress Semiconductor
Cypress Semiconductor



   PDF Click to Download PDF File

   PDF View for Mobile





Related Start with W15*

[ W15 ETC ]     [ W150 Cypress Semiconductor ]     [ W1505 TT electronics ]     [ W150NF55 STMicroelectronics ]     [ W152 Cypress Semiconductor ]     [ W155 Cypress Semiconductor ]     [ W158 Cypress Semiconductor ]     [ W15NA50 ST Microelectronics ]     [ W15NB50 ST Microelectronics ]     [ W15NK50Z STMicroelectronics ]     [ W15NK90Z ST Microelectronics ]     [ W1-07311APA-G0 Power Systems GmbH ]     [ W10 Leshan Radio Company ]     [ W10 GOOD-ARK Electronics ]     [ W10 Semtech Corporation ]     [ W10 Shanghai Sunrise Electronics ]     [ W10 EIC discrete Semiconductors ]     [ W10 Surge Components ]     [ W10 Shanghai Lunsure Electronic Tech ]     [ W10 American Microsemiconductor ]     [ W10F American Microsemiconductor ]    


Searches related to W155 part

Find Chips CBC RS online RUTRONIK 24
Component Distributors NexGen Digital Richardson RFPD ICC
Beyond Components NAC PEI-Genesis Powell Electronics
TME Ameya 360 Power & Signal Datasheets360
Freelance Electronics Sager Electronics Terminals & Connectors TTI

0  1  2  3  4  5  6  7  8  9  A  B  C  D  E  F  G  H  I  J  K  L  M  N  O  P  Q  R  S  T  U  V  W  X  Y  Z
@ 2014 :: DatasheetsPDF.com :: Semiconductors Datasheet Search & Download Site