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P2781 데이터시트 PDF




Alliance Semiconductor에서 제조한 전자 부품 P2781은 전자 산업 및 응용 분야에서
광범위하게 사용되는 반도체 소자입니다.


 

PDF 형식의 P2781 자료 제공

부품번호 P2781 기능
기능 General Purpose EMI Reduction IC
제조업체 Alliance Semiconductor
로고 Alliance Semiconductor 로고


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P2781 데이터시트, 핀배열, 회로
July 2005
P2781/82/84
rev 1.5
General Purpose EMI Reduction IC
Features
ƒ Provides up to 15dB of EMI suppression
ƒ FCC approved method of EMI attenuation
ƒ Generates a 1X, 2X, and 4X low EMI spread
spectrum clock of the input frequency
ƒ Input frequency range from 3 to 78MHz
ƒ External loop filter for spread % adjustment
ƒ Spreading ranges from ±0.25% to ±5.0%
ƒ Ultra low cycle-to-cycle jitter
ƒ Zero-cycle slip
ƒ 3.3V operating voltage range
ƒ 10 mA output drives
ƒ TTL or CMOS compatible outputs
ƒ Ultra-low power CMOS design
ƒ P278XA is available in 8 pin SOIC and TSSOP
Packages
ƒ Available for industrial and automotive
temperature ranges.
Product Description
other digital video and imaging applications. The P278xA
reduces electromagnetic interference (EMI) at the clock
source, which provides system wide reduction of EMI of
all clock dependent signals. The P278xA allows
significant system cost savings by reducing the number of
circuit board layers and shielding that are traditionally
required to pass EMI regulations.
The P278xA uses the most efficient and optimized
modulation profile approved by the FCC. The P278xA
modulates the output of a single PLL in order to “spread”
the bandwidth of a synthesized clock and, more
importantly, decreases the peak amplitudes of its
harmonics. This results in significantly lower system EMI
compared to the typical narrow band signal produced by
oscillators and most frequency generators. Lowering EMI
by increasing a signal’s bandwidth is called spread
spectrum clock generation.
Applications
The P278xA is a versatile spread spectrum frequency
modulator designed specifically for digital camera and
The P278xA is targeted towards MFP, xDSL, fax modem,
set-top box, USB controller, DSC, and embedded systems.
Block Diagram
FS0 FS1 LF
VDD
XIN /CLKIN
XOUT
Crystal
Oscillator
www.DataSheet4U.com
Frequency
Divider
Feedback
Divider
Modulation
PLL
Phase
Detector
VCO
Output
Divider
ModOUT
VSS
Alliance Semiconductor
2575, Augustine Drive Santa Clara, CA Tel: 408.855.4900 Fax: 408.855.4999 www.alsc.com
Notice: The information in this document is subject to change without notice.




P2781 pdf, 반도체, 판매, 대치품
July 2005
P2781/82/84
rev 1.5
Spread Spectrum Selection
The P278xA performs Zero Cycle Slip when set at low percentage spreading. This allows no occurrence of system timing
error. The optimal setting should minimize system EMI to the fullest without affecting system performance. The spreading is
described as a percentage deviation of the center frequency.
(Note: the center frequency is the frequency of the external reference input on CLKIN, Pin 1.)
The P2781A is designed for PC peripheral, networking, notebook PC, and LCD monitor applications. It is optimized for
operation between 3 to 78MHz range. In the following application schematic example, the P2781A spread percentage
selection is determined by the external LF value specified in the Loop Filter Selection Table. The Input Frequency Selection
Table specifies the input frequency range. The external LF allows the user to fine tune the spread percentage to optimize the
EMI reduction benefits of the spread spectrum.
16 MHz
1 XIN/CLKIN VDD 8
2 XOUT
FS0 7
2.2 K
0.1µF
+3.3V
3 FS1 ModOUT 6
Modulated 16MHz Clock
To target Chip
4 LF
VSS 5
R1
C2 C1 0 Ohm
P2781A
Note: Both logic input pins FS1 and FS0 have to be connected to either VDD or VSS. Do not leave them floating.
www.DataSheet4U.com
General Purpose EMI Reduction IC
Notice: The information in this document is subject to change without notice.
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P2781 전자부품, 판매, 대치품
July 2005
rev 1.5
Package Information
Mechanical Package Outline 8-Pin SOIC Package
P2781/82/84
EH
www.DataSheet4U.com
D
e
B
A2 A
A1
θ
C
L
Symbol
A1
A
A2
B
C
D
E
e
H
L
θ
Dimensions
Inches
Millimeters
Min Max
Min
Max
0.004
0.010
0.10
0.25
0.053
0.069
1.35
1.75
0.049
0.059
1.25
1.50
0.012
0.020
0.31
0.51
0.007
0.010
0.18
0.25
0.193 BSC
4.90 BSC
0.154 BSC
3.91 BSC
0.050 BSC
1.27 BSC
0.236 BSC
6.00 BSC
0.016
0.050
0.41
1.27
0° 8°
Note: Controlling dimensions are millimeters
SOIC - 0.074 grams unit weight
General Purpose EMI Reduction IC
Notice: The information in this document is subject to change without notice.
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관련 데이터시트

부품번호상세설명 및 기능제조사
P2781

General Purpose EMI Reduction IC

Alliance Semiconductor
Alliance Semiconductor
P2781

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ETAL

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