CY25901 Datasheet | Cypress

Features - - - - - - - Supports clock requirements for Spread Spectrum 40-MHz Spread Spectrum clock output Reference clock output Two spread bandwidths: 1%, 3% External clock or Cera-Lock input 3.3V operation 8-pin SOIC package Description The CY25901 clock generator provides a low-electromagnetic interference (EMI) clock output. It features Spread Spectrum technology, a modulation technique designed specifically for reducing EMI at the fundamental frequency and its harmonics. Table 1. Function Table CLKOUT (Spread Spectrum) SSSEL 0 1 X (don’t care) SSON 0 0 1 REFOUT XIN XIN XIN CY25901SC = XIN ± 0.35% (0.7% center) = XIN ± 1.20% (2.4% center) = XIN (No Spread) CY25901SC-1 = XIN ± 0.5% (1.0% center) = XIN ± 1.5% (3.0% center) = XIN (No Spread) Block Diagram Pin Configuration XIN Oscillator XOUT REFOUT CLKOUT VDD VSS XIN 1 2 3 4 8 7 6 5 SSON# REFOUT SSSEL XOUT SSON SSSEL PLL CLKOUT SSCG Cypress Semiconductor Corporation Document #: 38-07521 Rev. - - - 3901 North First Street - San Jose, CA 95134 - 408-943-2600 Revised February 18, 2003 Pin Description Pin No. 1 2 3 4 5 6 7 8 Name CLKOUT VDD VSS XIN XOUT SSSEL REFOUT SSON# I/O O PWR PWR I O I O I Power Supply. mon Ground. Oscillator Buffer Input. Connect to an external parallel resonant crystal or externally generated reference clock. Oscillator Buffer Output. Connect to an external parallel resonant crystal. Do not connect when an externally generated reference clock is applied at XIN. Spread Spectrum Select Input. See Table 1. internally pulled up. Buffered Output of XIN. Spread Spectrum Enable Input. When asserted low, Spread Spectrum is enabled. Internally pulled down. radiated energy over the spectrum. This technique is achieved by modulating the clock around or below the center of its reference frequency by a certain percentage (which also determines the energy distribution bandwidth). The SSCG function is enabled when SSON pin is set to low. Resulting in a spread bandwidth that is...