下载
CY25100
Field and Factory Programmable Spread
Spectrum Clock Generator for EMI Reduction
Cypress Semiconductor Corporation • 198 Champion Court • San Jose, CA 95134-1709 • 408-943-2600
Document Number: 38-07499 Rev. *K Revised November 28, 2014
Field and Fa ctory Programmab le Spread Spectrum Clock Generator for EMI Redu ction
Features
■ Wide Operating Output (SSCLK) Frequency Range
❐ 3 MHz to 200 MHz
■ Programmable Spread Spectrum with nominal 31.5 kHz
Modulation Frequency
❐ Center Spread: ±0.25% to ±2.5%
❐ Down Spread: –0.5% to –5.0%
■ Input frequency range
❐ External Crystal: 8 to 30 MHz Fundamental Crystals
❐ External Reference: 8 to 166 MHz Clock
■ Integrated Phase-Locked Loop (PLL)
■ Field Programmable devices available
■ Programmable Crystal Load Capacitor Tuning Array
■ Low Cycle-to-cycle Jitter
■ Spread Spectrum on/off function
■ Powerdown or Output Enable function
■ Commercial and Industrial temperature ranges
■ 3.3 V operation
■ 8-pin TSSOP and SOIC packages
Functional Description
The CY25100 is a Spread Spectrum Clock Generator (SSCG) IC
used to reduce EMI found in today’s high speed digital electronic
systems.
The device uses a Cypress proprietary PLL and Spread
Spectrum Clock (SSC) technology to synthesize and modulate
the frequency of the input clock. By frequency modulating the
clock, the measured EMI at the fundamental and harmonic
frequencies are greatly reduced. This reduction in radiated
energy can significantly reduce the cost of complying with
regulatory agency (EMC) requirements and improve
time-to-market without degrading system performance.
The CY25100 uses a factory or field-programmable
configuration memory array to synthesize output frequency,
spread percentage, crystal load capacitor, reference clock output
on/off, spread spectrum on/off function, and PD#/OE options.
The spread percentage is programmed to either center spread
or down spread with various spread percentages. The range for
center spread is from ±0.25% to ±2.50%. The range for down
spread is from –0.5% to –5.0%.
The input to the CY25100 can either be a crystal or a clock
signal. The CY25100 has two clock outputs: REFCLK and
SSCLK. The non-spread spectrum REFCLK output has the
same frequency as the input of the CY25100.
For a complete list of related documentation, click here.
Logic Block Diagram
PLL
with
MODULATION
CONTROL
PROGRAMMABLE
CONFIGURATION
OUTPUT
DIVIDERS
and
MUX
3
2
4
8
1 5
7
6
VDD VSS
REFCLK
SSCLK
XOUT
XIN
PD# or OE
SSON#
RFB
C
XOUT
CXIN
页面指南
