Provides 15dB of EMI suppression FCC approved method of EMI attenuation Generates a 1X low EMI spread spectrum clock of the input frequency Operates between 20MHz and 38MHz input frequency range External loop filter for spread percentage adjustment Spreading ranges from to �2.5% Ultra low cycle-to-cycle jitter Zero-Cycle slip at small deviations 3.3 V Operating Voltage 10 mA output drives TTL or CMOS compatible outputs Low power CMOS design Available in 8-pin SOIC and TSSOP Packages Available for Industrial temperature operating range 85� C)

the clock source, which provides system-wide reduction of EMI of all clock dependent signals. The P2779A allows significant system cost savings by reducing the number of circuit board layers and shielding that are traditionally required to pass EMI regulations. The P2779A uses the most efficient and optimized modulation profile approved by the FCC. The P2779A modulates the output of a single PLL in order to spread the bandwidth of a synthesized clock and, more importantly, decreases 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 frequency generators. Lowering EMI by increasing a signal's bandwidth is called spread spectrum clock generation.

The is a versatile spread spectrum frequency modulator designed specifically for mobile and digital camera and other digital video and imaging applications. The P2779A reduces electromagnetic interference (EMI) at

Alliance Semiconductor 2575, Augustine Drive Santa Clara, CA Tel: 408.855.4900 Fax: 408.855.4999 www.alsc.com

Connect to crystal or clock input. Crystal output. Power-down control pin. Pull low to enable power-down mode. 1 This pin has an internal pull-up resistor. External loop filter for the PLL. By changing the value of the CRC circuit, the percentage spread can be adjusted accordingly. (See Loop Filter Selection Table for detail values.) Ground connection. Connect to system ground. Spread spectrum clock output. Provides a reference clock output of the input frequency. Connect +3.3 V.

The P2779A performs zero cycle slip when set at low percentage spreading. This prevents any occurrence of system timing error. The optimal setting should minimize system EMI to the fullest without affecting system performance. The spreading is described as a percentage deviation of the center frequency. (Note that the center frequency is the frequency of the external reference input on XIN/CLKIN, pin 1.) The P2779A is designed for PC peripheral, networking, notebook PC, and LCD monitor applications. It is optimized for operation from to 38MHz. The P2779A's spread percentage selection is determined by the external LF value specified in the Loop Filter Selection Table. The external LF allows the user to fine tune the spread percentage to optimize the EMI reduction benefits of the spread spectrum.