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P2781 Schematic ( PDF Datasheet ) - ON Semiconductor

Teilenummer P2781
Beschreibung General Purpose EMI Reduction IC
Hersteller ON Semiconductor
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Gesamt 8 Seiten
P2781 Datasheet, Funktion
P2781/82/84
General Purpose EMI
Reduction IC
Features
Provides up to 15dB of EMI suppression
FCC approved method of EMI attenuation
Generates a 1X, 2X, and 4X low EMI spread spectrum
clock of the input frequency
Input frequency range from 3 to 78MHz
External loop filter for spread % adjustment
Spreading ranges from ±0.25% to ±5.0%
Ultra low cycle-to-cycle jitter
Zero-cycle slip
3.3V operating voltage range
Ultra-low power CMOS design
P278xA is available in an 8 pin SOIC Package
Product Description
The P278xA is a versatile spread spectrum frequency
modulator designed specifically for digital camera and 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 result 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 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
©2010 SCILLC. All rights reserved.
JANUARY 2010 – Rev. 2
VSS
Publication Order Number:
P2781/82/84






P2781 Datasheet, Funktion
P2781/82/84
AC Electrical Characteristics
Symbol
Parameter
fIN Input frequency: P278xA
P2781A
fOUT Output frequency:
P2782A
P2784A
tLH
P278xA
Output rise time (measured at 0.8V to 2.0V,
25pF scope probe loading)
tHL
P278xA
Output fall time (measured at 2.0V to 0.8V, 25
pF scope probe loading)
tJC
P2781A
Jitter (cycle-to-cycle, ±6sigma, 1000 sweeps,
±0.5% spread, I/O frequency = 16MHz)
tD
P2781A
Output duty cycle deviation (error from 50%
duty cycle, 25pF scope probe loading)
F
P278xA
Frequency deviation tolerance from BW%
stated in the Loop Filter Selection Table
Min
3
3
6
12
±1 @ 3MHz
-20
Typ
1
1
±250
Max
78
78
156
312
Unit
MHz
nS
nS
pS
±2 @ 82MHz %
0 +20 %
www.DataSheet4U.com
Rev. 2 | Page 6 of 8 | www.onsemi.com

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