ASM3P2190A Datasheet, PDF (1/7 Pages) Alliance Semiconductor Corporation – Peak Reducing EMI Solution

November 2003
rev 1.0
ASM3P2190A
Peak Reducing EMI Solution
Features
• Generates an EMI optimized clocking
signal at the output.
• Selectable output frequency range.
• Single 1.25% or 2.4% down spread
output.
• Integrated loop filter components.
• Operates with a 3.3V supply.
• Low-power CMOS design.
• Available in 8-pin SOIC and 8-pin
TSSOP packages.
Product Description
The ASM3P2190A is a versatile spread spectrum
frequency modulator designed specifically for a
wide range of clock frequencies. The
ASM3P2190A reduces electromagnetic
interference (EMI) at the clock source, allowing
system wide reduction of EMI of down stream
clock and data dependent signals. The
ASM3P2190A allows significant system cost
savings by reducing the number of circuit board
layers and shielding that are traditionally required
to pass EMI regulations.
The ASM3P2190A modulates the output of a
single PLL in order to “spread” the bandwidth of a
synthesized clock, thereby decreasing 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 clock generators. Lowering
EMI by increasing a signal’s bandwidth is called
spread spectrum clock generation.
The ASM3P2190A uses the most efficient and
optimized modulation profile approved by the
FCC and is implemented by using a proprietary
all-digital method.
Applications
The ASM3P2190A is targeted towards notebook
LCD displays, other displays using an LVDS
interface, PC peripheral devices and embedded
systems.
Key Specifications
Description
Supply voltages
Frequency range
Cycle-to-cycle jitter
Selectable spread percentage
Output duty cycle
Output rise and fall time
Specification
V_DD = 3.3V ± 5%
6 MHz ≤ 30 MHz
325 ps (typical)
-1.25% or –2.4%
40/60% (worst case)
5ns (maximum)
Simplified Block Diagram
X1
X2
3.3V
Spread spectrum output
(EMI suppressed)
Pin Diagram
CLKIN / X1 1
8 NC
NC / X2
GND
2
7 ^FS1
ASM3P2190A
3
6 ^VDD
SS% 4
5 CLKOUT
Alliance Semiconductor
2595, Augustine Drive • Santa Clara • CA 95054 • Tel [phone] • Fax [phone] • www.alsc.com
Notice: The information in this document is subject to change without notice.