ASM3P2579A Datasheet, PDF (1/7 Pages) Alliance Semiconductor Corporation – Low Power Peak EMI Reducing Solution

ASM3P2579A
Peak EMI
Reducing Solution
Features
• Generates an EMI optimized clock signal at the
output.
• Integrated loop filter components.
• Operates with a 3.3 / 2.5V Supply.
• Operating current less than 4mA.
• CMOS design.
• Input frequency range: 12MHz to 30MHz for 2.5V
12MHz to 30MHz for 3.3V
• Generates a 1X low EMI spread spectrum clock of
the input frequency.
• Spread Spectrum Enable Control.
• Frequency deviation: ±1% @ 24MHz
• Available in 6L-TSOP (6L-TSOT-23).
Product Description
The ASM3P2579A is a versatile spread spectrum
frequency modulator designed specifically for a wide
range of clock frequencies. The ASM3P2579A reduces
electromagnetic interference (EMI) at the clock source,
allowing system wide reduction of EMI of all clock
dependent signals. The ASM3P2579A 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.
-The ASM3P2579A uses the most efficient and optimized
modulation profile approved by the FCC and is
implemented by using a proprietary all digital method.
The ASM3P2579A 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 ASM3P2579A is targeted towards all portable
devices like MP3 players and digital still cameras.
Key Specifications
Description
Supply voltages
Cycle-to-Cycle Jitter
Output Duty Cycle
Modulation Rate Equation
Frequency Deviation
Specification
VDD = 3.3V/2.5V
±200pS (Typ)
45/55% (worst case)
FIN/640
±1% @ 24MHz
Block Diagram
VDD
SSON
XIN
XOUT
Crystal
Oscillator
Frequency
Divider
Feedback
Divider
Modulation
Phase
Detector
Loop
Filter
PLL
VCO
Output
Divider
ModOUT
VSS
©2010 SCILLC. All rights reserved.
JANUARY 2010 – Rev. 2
Publication Order Number:
ASM3P2579/D