ASM3P2508A Datasheet, PDF (1/8 Pages) Alliance Semiconductor Corporation – Peak EMI Reducing Solution

ASM3P2508A
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Peak EMI Reducing
Solution
Description
The ASM3P2508A is a versatile spread spectrum frequency
modulator. The ASM3P2508A reduces electromagnetic interference
(EMI) at the clock source. The ASM3P2508A allows significant
system cost savings by reducing the number of circuit board layers and
shielding that are required to pass EMI regulations. The
ASM3P2508A 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.
The ASM3P2508A has a feature to power down the 72 MHz /
48 MHz output by writing data into specific registers in the device via
I2C. By writing a ‘0’ into bit 1 of Byte 0, the PLL block generating
72 MHz / 48 MHz can be powered down. Writing ‘0’ into bit ‘7’ of
Byte 1 selects an output of 72 MHz on FOUT2CLK while a ‘1’ at the
same location selects a 48 MHz clock output. However, the I2C block,
crystal oscillator, and the PLL block generating 120 MHz would be
always running.
Features
• Generates an EMI Optimized Clocking Signal at Output
• Input Frequency − 14.31818 MHz
• Frequency Outputs:
− 120 MHz (modulated) − Default
− 72 MHz (modulated) or 48 MHz (modulated) Selectable via I2C
• ±1% Centre Spread
• Modulation Rate: 40 KHz
• Byte Write via I2C
• Supply Voltage Range 3.3 V ± 0.3 V
• Available in 8−pin SOIC Package
• Available in Commercial and Industrial
• Temperature Ranges
• These Devices are Pb−Free, Halogen Free/BFR Free and are RoHS
Compliant
This document contains information on a product under development. ON Semiconductor
reserves the right to change or discontinue this product without notice.
http://onsemi.com
SOIC−8
S SUFFIX
CASE 751BD
PIN CONFIGURATION
1
XIN
V_SS
XOUT
SCL
V_DD
SDA
FOUT1CLK
FOUT2CLK
(Top View)
ORDERING INFORMATION
See detailed ordering and shipping information in the package
dimensions section on page 8 of this data sheet.
© Semiconductor Components Industries, LLC, 2011
1
August, 2011 − Rev. P3
Publication Order Number:
ASM3P2508A/D