ASM3P2879A Datasheet, PDF (1/12 Pages) Alliance Semiconductor Corporation – Low Power Peak Reducing EMI Solution

January 2007
rev 1.5
ASM3P2879A
Low Power Peak Reducing EMI Solution
Features
• Generates an EMI optimized clock signal at the
output.
• Integrated loop filter components.
• Operates with a 3.3V /2.5V Supply.
• Operating current less than 4mA.
• Low power CMOS design.
• 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% @ 24MHz
• Available in 6-pin TSOT-23, 8-pin SOIC and 8-pin
TSSOP packages.
Product Description
The ASM3P2879A is a versatile spread spectrum
frequency modulator designed specifically for a wide
range of clock frequencies. The ASM3P2879A reduces
electromagnetic interference (EMI) at the clock source,
allowing system wide reduction of EMI of all clock
dependent signals. The ASM3P2879A allows significant
system cost savings by reducing the number of circuit
board layers ferrite beads, shielding that are traditionally
required to pass EMI regulations.
Block Diagram
VDD
The ASM3P2879A uses the most efficient and optimized
modulation profile approved by the FCC and is
implemented by using a proprietary all digital method.
The ASM3P2879A 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 ASM3P2879A is targeted towards all portable
devices with very low power requirements like MP3
players, Notebooks and digital still cameras.
Key Specifications
Description
Supply voltages
Cycle-to-Cycle Jitter
Output Duty Cycle
Modulation Rate Equation
Frequency Deviation
Specification
VDD = 2.5V / 3.3V
200pS (Max)
45/55%
F_IN/640
±1% @ 24MHz
XIN
XOUT
Crystal
Oscillator
REFOUT
Frequency
Divider
Feedback
Divider
Modulation
Phase
Detector
Loop
Filter
PLL
VCO
Output
Divider
ModOUT
VSS
PulseCore Semiconductor Corporation
1715 S. Bascom Ave Suite 200, Campbell, CA 95008 • Tel: [phone] • Fax: [phone]
www.pulsecoresemi.com
Notice: The information in this document is subject to change without notice.