ASM3P2111A Datasheet, PDF (1/8 Pages) Alliance Semiconductor Corporation – Peak EMI Reducing Solution

March 2005
rev 1.3
ASM3P2111A
Peak EMI Reducing Solution
Features
ƒ Generates an EMI optimized clocking signal at
output.
ƒ Input frequency – 25 MHz.
ƒ Frequency outputs:
o 60 MHz (unmodulated)
o 2 x 48 MHz (unmodulated)
o 66.6 MHz (modulated) -1.7% down spread
ƒ Modulation rate: 30 KHz.
ƒ Supply voltage range: 3.3V ± 0.3V.
ƒ Available in 8-pin SOIC Package.
ƒ Commercial and Industrial Temperature range.
The ASM3P2111A allows significant system cost savings
by reducing the number of circuit board layers and
shielding that are required to pass EMI regulations. The
ASM3P2111A modulates the output of 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.
Applications
Product Description
The ASM3P2111A is a versatile spread spectrum
frequency modulator. The ASM3P2111A reduces
electromagnetic interference (EMI) at the clock source.
ASM3P2111A is targeted towards EMI management for
high speed digital applications such as PC peripheral
devices, consumer electronics and embedded controller
systems.
Block Diagram
V_DD
XIN /CLKIN
XOUT
Crystal
Oscillator
48 MHz_1
PLL1
PLL2
60 MHz
48 MHz_1
48 MHz_2
66.6 MHz
Modulated
V_SS
Alliance Semiconductor
2575 Augustine Drive • Santa Clara CA • Tel: [phone] • Fax: [phone] • www.alsc.com