ASM3P2779A
Peak EMI
Reducing Solution
Features
• Generates an EMI optimized clock signal at the
The ASM3P2779A uses the most efficient and optimized
modulation profile approved by the FCC and is
implemented by using a proprietary all digital method.
output.
• Integrated loop filter components.
• Operates with a 3.3 / 2.5V Supply.
• Operating current less than 4mA.
• CMOS design.
The ASM3P2779A 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.’
• Input frequency range: 13MHz to 30MHz for 2.5V
13MHz to 30MHz for 3.3V
• Generates a 1X low EMI spread spectrum clock of
the input frequency.
• Frequency deviation: ±1% (Typ) @ 16MHz Input
Frequency.
Applications
The ASM3P2779A is targeted towards all portable
devices like MP3 players and digital still cameras.
• Available in 6L-TSOP (6L-TSOT-23).
Product Description
The ASM3P2779A is
Key Specifications
a versatile spread spectrum
Description
Supply voltages
Specification
VDD = 3.3V / 2.5V
frequency modulator designed specifically for a wide
range of clock frequencies. The ASM3P2779A reduces
electromagnetic interference (EMI) at the clock source,
allowing system wide reduction of EMI of all clock
dependent signals. The ASM3P2779A allows significant
system cost savings by reducing the number of circuit
board layers, ferrite beads and shielding that are
traditionally required to pass EMI regulations.
Cycle-to-Cycle Jitter
Output Duty Cycle
±200pS (Typ)
45/55%
Modulation Rate Equation
Frequency Deviation
FIN/640
±1% (Typ) @ 16MHz
Block Diagram
VDD
PD
PLL
Modulation
XIN / CLKIN
XOUT
Crystal
Oscillator
Frequency
Divider
Output
Divider
Phase
Detector
Loop
Filter
VCO
Feedback
Divider
ModOUT
VSS
©2010 SCILLC. All rights reserved.
JANUARY 2010 – Rev. 4
Publication Order Number:
ASM3P2779/D