Document
May 2008 rev 0.1
PCS3P622Z05B/C PCS3P622Z09B/C
Low Frequency Timing-Safe™ Peak EMI reduction IC
www.DataSheet4U.com
General Features
• • • Low Frequency Clock distribution with TimingSafe™ Peak EMI Reduction Input frequency range: 4MHz - 20MHz Multiple low skew Timing-safe™ Outputs: PCS3P622Z05: 5 Outputs PCS3P622Z09: 9 Outputs • • • • External Input-Output Delay Control option Supply Voltage: 3.3V±0.3V Commercial and Industrial temperature range Packaging Information: ASM3P622Z05: 8 pin SOIC, and TSSOP ASM3P622Z09:16 pin SOIC, and TSSOP • True Drop-in Solution for Zero Delay Buffer, ASM5P2305A / 09A
designed to distribute low frequency Timing-Safe™ clocks with Peak EMI reduction. PCS3P622Z05 is an eight-pin version, accepts one reference input and drives out five low-skew Timing-Safe™ clocks. PCS3P622Z09 accepts one reference input and drives out nine low-skew TimingSafe™clocks. PCS3P622Z05/09 has a DLY_CTRL for adjusting the Input-Output clock delay, depending upon the value of capacitor connected at this pin to GND. PCS3P622Z05/09 operates from a 3.3V supply and is available in two different packages, as shown in the ordering information table, over commercial and Industrial temperature range.
Application
PCS3P622Z05/09 is targeted for use in Displays and memory interface systems.
Functional Description
PCS3P622Z05/09 is a versatile, 3.3V Zero-delay buffer
General Block Diagram
PLL CLKIN
DLY_CTRL CLKOUT1 CLKOUT2 CLKIN
PLL
MUX
DLY_CTRL CLKOUTA1 CLKOUTA2 CLKOUTA3
CLKOUT3
CLKOUTA4 S2 S1 CLKOUTB1 Select Input Decoding CLKOUTB2 CLKOUTB3
PCS3P622Z05B/C
CLKOUT4
PCS3P622Z09B/C
CLKOUTB4
PulseCore Semiconductor Corporation 1715 S. Bascom Ave Suite 200 Campbell, CA 95008 • Tel: 408-879-9077 • Fax: 408-879-9018 www.pulsecoresemi.com
Notice: The information in this document is subject to change without notice.
May 2008 rev 0.1
Spread Spectrum Frequency Generation
The clocks in digital systems are typically square waves with a 50% duty cycle and as frequencies increase the edge rates also get faster. Analysis shows that a square wave is composed of fundamental frequency and harmonics. The fundamental frequency and harmonics generate the energy peaks that become the source of EMI. Regulatory agencies test electronic equipment by measuring the amount of peak energy radiated from the equipment. In fact, the peak level allowed decreases as the frequency increases. The standard methods of reducing EMI are to use shielding, filtering, multi-layer
PCS3P622Z05B/C PCS3P622Z09B/C
www.DataSheet4U.com PCBs etc. These methods are expensive. Spread
spectrum clocking reduces the peak energy by reducing the Q factor of the clock. This is done by slowly modulating the clock frequency. The PCS3P622Z05/09 uses the center modulation spread spectrum technique in which the modulated output frequency varies above and below the reference frequency with a specified modulation rate. With center modulation, the average frequency is the same as the unmodulated fre.