ASM3P2508A Datasheet | Alliance Semiconductor Corporation

Features Generates an EMI optimized clocking signal at output. Input frequency - 14.31818 MHz. Frequency outputs: o o 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 3.3V ± 0.3V. Available in 8-pin SOIC Package. Available in mercial and Industrial Temperature ranges. 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 pared 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 72MHz/48MHz 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 / 48MHz 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 Product Description The ASM3P2508A is a versatile spread spectrum frequency modulator. The ASM3P2508A reduces electromagnetic interference (EMI) at the clock source. location selects a 48 MHz clock output. However, the I2C block, crystal oscillator, and the PLL block generating 120MHz would be always running. Block Diagram XIN XOUT Crystal Oscillator PLL 1 FOUT1CLK (120 MHz) SCL SDA I2C Interface PLL 2 FOUT2CLK (72 MHz / 48 MHz) Alliance Semiconductor 2575 Augustine Drive - Santa Clara CA - Tel: 408-855-4900 - Fax: 408-855-4999 - .alsc. February 2005 .. ASM3P2508A rev 1.3 Pin Configuration XIN XOUT VDD FOUT1CLK 1 2 8 7 SCL SDA FOUT2CLK 3 4 6 5 Pin Description Pin Name XIN XOUT...