FCC approved method of EMI attenuation.
Generates a 1X low EMI spread spectrum clock of
the input frequency.
Input frequency range: 15MHz – 27MHz.
Internal loop filter minimizes external components
and board space.
Frequency deviation: -2.5%
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, 24MHz
Pinout compatible with Cypress CY25811.
Products are available for industrial temperature
Available in 8-pin SOIC and TSSOP.
The ASM3P2821B is a versatile spread spectrum
frequency modulator designed specifically for input clock
frequencies in the range of 15MHz - 27MHz. The
ASM3P2821B can generate an EMI reduced clock from a
ceramic resonator or system clock. The ASM3P2821B
offers a percentage deviation of –2.5%.
The ASM3P2821B reduces electromagnetic interference
(EMI) at the clock source, allowing system wide reduction
of EMI of down stream clock and data dependent
signals. The ASM3P2821B 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 ASM3P2821B uses the most efficient and optimized
modulation profile approved by the FCC and is
implemented in a proprietary all digital method.
The ASM3P2821B 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’.
The ASM3P2821B is targeted towards EMI management
for high speed digital applications such as PC peripheral
devices, consumer electronics and embedded controller
2575, Augustine Drive • Santa Clara, CA • Tel: 408.855.4900 • Fax: 408.855.4999 • www.alsc.com
Notice: The information in this document is subject to change without notice.