ASM3P5821A Datasheet, PDF (1/7 Pages) Alliance Semiconductor Corporation – Low Power EMI Reduction IC

October 2003
rev 1.0
ASM3P5821A
Features
FCC approved method of EMI attenuation.
Generates a 1X low EMI spread spectrum clock of
the input frequency.
Input frequency range: 20MHz –34MHz.
Internal loop filter minimizes external components
and board space.
Frequency deviation: -1.5%
Low inherent cycle-to-cycle jitter.
3.3V operating voltage.
TTL or CMOS compatible inputs and outputs.
Ultra-low power CMOS design.
o TBD mA @ 3.3V, 25MHz
o TBD mA @ 3.3V, 31MHz
Pinout compatible with Cypress CY25811.
Products are available for industrial temperature
range.
Available in 8-pin SOIC and TSSOP.
Product Description
The ASM3P5821A is a versatile spread spectrum
frequency modulator designed specifically for input clock
frequencies in the range of 20MHz – 34MHz. The
ASM3P5821A can generate an EMI reduced clock from
crystal, ceramic resonator, or system clock. The
ASM3P5821A offers a percentage deviation of –1.5%.
The ASM3P5821A reduces electromagnetic interference
(EMI) at the clock source, allowing system wide reduction
of EMI of down stream clock and data dependent
signals. The ASM3P5821A allows significant system cost
savings by reducing the number of circuit board layers
ferrite beads, shielding and other passive components
that are traditionally required to pass EMI regulations.
The ASM3P5821A uses the most efficient and optimized
modulation profile approved by the FCC and is
implemented in a proprietary all digital method.
The ASM3P5821A 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 ASM3P5821A is targeted towards EMI management
for high speed digital applications such as PC peripheral
devices, consumer electronics and embedded controller
systems.
Block Diagram
XIN
XOUT
Crystal
Oscillator
Frequency
Divider
Feedback
Divider
Modulation
Phase
Detector
VDD
PLL
Loop
Filter
VCO
Output
Divider
MODOUT
VSS
Alliance Semiconductor
2575, Augustine Drive • Santa Clara, CA • Tel: [phone] • Fax: [phone] • www.alsc.com
Notice: The information in this document is subject to change without notice.