FS781/82/84
Low EMI Spectrum Spread Clock
Features
鈥?Spread Spectrum clock generator (SSCG) with 1脳, 2脳,
and 4脳 outputs
鈥?6- to 82-MHz operating frequency range
鈥?Modulates external clocks including crystals, crystal
oscillators, or ceramic resonators
鈥?Programmable modulation with simple R-C external
loop filter (LF)
鈥?Center spread modulation
鈥?3V-5V power supply
鈥?TTL-/CMOS-compatible outputs
鈥?Low short-term jitter
鈥?Low-power Dissipation
鈥?3.3 VDC = 37 mW 鈥?typical
鈥?5.0 VDC = 115 mW 鈥?typical
鈥?Available in 8-pin SOIC and TSSOP packages
Description
The Cypress FS781/82/84 are Spread Spectrum clock
generator ICs (SSCG) designed for the purpose of reducing
electromagnetic interference (EMI) found in today鈥檚
high-speed digital systems.
The FS781/82/84 SSCG clocks use a Cypress-proprietary
technology to modulate the input clock frequency, XIN, by
modulating the frequency of the digital clock. By modulating
the reference clock the measured EMI at the fundamental and
harmonic frequencies of FSOUT is greatly reduced. This
reduction in radiated energy can significantly reduce the cost
of complying with regulatory requirements without degrading
digital waveforms.
The Cypress FS781/82/84 clocks are very simple and
versatile devices to use. By programming the two range select
lines, S0 and S1, any frequency from 6- to 82-MHz operating
range can be selected. The FS781/2/4 are designed to
operate over a very wide range of input frequencies and
provides 1脳, 2脳, and 4脳 modulated clock outputs.
The FS78x devices have a simple frequency selection table
that allows operation from 6 MHz to 82 MHz in four separate
ranges. The bandwidth of the frequency spread at FSOUT is
determined by the values of the loop filter components. The
modulation rate is determined internally by the input frequency
and the selected input frequency range.
The Bandwidth of these products can be programmed from as
little as 1.0% up to as much as 4.0% by selecting the proper
loop filter value. Refer to the Loop Filter Selection chart in
Table 2
and
Table 3
for the recommended values. Due to a
wide range of application requirements, an external loop filter
(LF) is used on the FS78x products. The user can select the
exact amount of frequency modulation suitable for the appli-
cation. Using a fixed internal loop filter would severely limit
the use of a wide range of modulation bandwidths (Spread %)
to a few discrete values. Refer to FS791/2/4 products for appli-
cations requiring 80- to 140-MHz frequency range.
Applications
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Desktop/notebook computers
Printers, copiers, and MFP
Scanners and fax
LCD displays and monitors
CD-ROM, VCD, and DVD
Automotive and embedded systems
Networking, LAN/WAN
Digital cameras and camcorders
Modems
Benefits
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Programmable EMI reduction
Fast time to market
Lower cost of compliance
No degradation in rise/fall times
Lower component and PCB layer count
Block Diagram
Loop Filter
4(6)
250 K
Pin Configuration
Xin
Xout
Reference
Divider
1
2
3
4
FS78x
8
7
6
5
VDD
S0
FSOUT
VSS
S1
Phase
Detector
VCO
10 pF.
Xin
1(3)
8 pF
LF
Xout
Modulation
Control
2(4)
8 Pin SOIC Package
8 pF
VCO / N
S0
VDD
8(2)
1
2
3
4
FS78x
8
7
6
5
FSOUT
VSS
LF
S1
Power Contol
Logic
VDD
Input Control Logic
Output
Divider
and
Mux
VSS
VDD
6(8)
FSOUT
Xin
Xout
5(7)
3(5)
7(1)
(TSSOP Pin #)
VSS
S1
S0
8 Pin TSSOP Package
Cypress Semiconductor Corporation
Document #: 38-07029 Rev. *C
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3901 North First Street
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San Jose
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CA 95134 鈥?408-943-2600
Revised December 14, 2002
FS781/82/84相關(guān)型號PDF文件下載
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英文版
Low EMI Spectrum Spread Clock
CYPRESS [C...
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英文版
Low EMI Spectrum Spread Clock
CYPRESS [C...
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英文版
Low EMI Spectrum Spread Clock
CYPRESS [C...
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英文版
MISCELLANEOUS CLOCK GENERATOR|TSSOP|8PIN|PLASTIC
ETC
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英文版
MISCELLANEOUS CLOCK GENERATOR|TSSOP|8PIN|PLASTIC
ETC
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英文版
MISCELLANEOUS CLOCK GENERATOR|TSSOP|8PIN|PLASTIC
ETC
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英文版
MISCELLANEOUS CLOCK GENERATOR|SOP|8PIN|PLASTIC
ETC
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英文版
MISCELLANEOUS CLOCK GENERATOR|SOP|8PIN|PLASTIC
ETC
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英文版
MISCELLANEOUS CLOCK GENERATOR|SOP|8PIN|PLASTIC
ETC
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英文版
MISCELLANEOUS CLOCK GENERATOR|SOP|8PIN|PLASTIC
ETC
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英文版
MISCELLANEOUS CLOCK GENERATOR|SOP|8PIN|PLASTIC
ETC
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英文版
Clocks and Buffers
ETC
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