CY25100 Cypress Semiconductor, CY25100 Datasheet - Page 2

• Manufacturer Part Number: CY25100
• Description: Field- and Factory-Programmable Spread Spectrum Clock Generator for EMI Reduction
• Manufacturer: Cypress Semiconductor

Document #: 38-07499 Rev. *D
Pin Description
General Description
The CY25100 is a Spread Spectrum Clock Generator (SSCG)
IC used for the purpose of reducing 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
time-to-market without degrading system performance.
The CY25100 uses a factory/field-programmable configu-
ration memory array to synthesize output frequency, spread%,
crystal load capacitor, reference clock output on/off, spread
spectrum on/off function and PD#/OE options.
Table 1.
1
2
3
4
5
6
7
8
Pin Name
Function
Program
Value
Pin#
Unit
Pin
Pin
agency
ENTER DATA ENTER DATA
Frequency
XIN and
3 and 2
XOUT
Input
MHz
VDD
XOUT
XIN/CLKIN
PD#/OE
VSS
REFCLK
SSCLK
SSON#
(EMC)
XIN and XOUT
Capacitance
Name
requirements
Total Xtal
3 and 2
Load
pF
3.3V power supply.
Crystal output. Leave this pin floating if external clock is used.
Crystal input or reference clock input.
Power-down pin: Active LOW. If PD# = 0, the PLL and Xtal are powered down,
and outputs are weakly pulled low.
Output Enable pin: Active HIGH. If OE = 1, SSCLK and REFCLK are enabled.
User has the option of choosing either PD# or OE function.
Power supply ground.
Buffered reference output.
Spread spectrum clock output.
Spread spectrum control. 0 = Spread on. 1 = Spread off.
Frequency
and
ENTER
Output
SSCLK
DATA
MHz
7
improve
0.25% Intervals)
Spread Percent
ENTER DATA
(0.5% – 5%,
The spread% 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%. Contact the factory for smaller or
larger spread % amounts if required.
The input to the CY25100 can be either a crystal or a clock
signal. The input frequency range for crystals is 8–30 MHz,
and for clock signals is 8–166 MHz.
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. The frequency
modulated SSCLK output can be programmed from 3–200
MHz.
The CY25100 products are available in an 8-pin SOIC and
TSSOP packages with commercial and industrial operating
temperature ranges.
SSCLK
%
7
Description
Reference
REFOUT
On or Off
ENTER
Output
DATA
6
Select PD# or OE
Power-down or
Output Enable
ENTER DATA
PD#/OE
4
CY25100
Modulation
Page 2 of 11
Frequency
SSCLK
31.5
kHz
7