ASM3P2853A Datasheet, PDF (1/7 Pages) Alliance Semiconductor Corporation – Peak EMI Reducing Solution

ASM3P2853A
Peak EMI Reducing Solution
Features
• Generates an EMI optimized clock signal at output.
• Input frequency: 25MHz.
• Frequency outputs:
o USB Clock (48MHz unmodulated)
o 50MHz (modulated), ±1% centre spread
• Modulation rate: 39KHz.
• Spread Spectrum ON/OFF control
• Supply voltage range 2.5V ± 5%.
• Available in 8-Pin SOIC package.
Product Description
The ASM3P2853A is a versatile spread spectrum
frequency modulator. The ASM3P2853A reduces
electromagnetic interference (EMI) at the clock source.
The ASM3P2853A allows significant system cost savings
by reducing the number of circuit board layers and
shielding that are required to pass EMI regulations. The
ASM3P2853A 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
ASM3P2853A 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
PWDNB
XIN
XOUT
SSONB
Crystal
Oscillator
VSS
PLL1
PLL2
USB Clock
(48MHz
Unmodulated)
50MHz
Modulated
©2010 SCILLC. All rights reserved.
JANUARY 2010 – Rev. 2
Publication Order Number:
ASM3P2853/D