CY25811/12/14
Document #: 38-07112 Rev. *E
Page 2 of 11
Functional Description
The CY25811/12/14 products are Spread Spectrum Clock
Generator (SSCG) ICs used for the purpose of reducing
electromagnetic
interference
(EMI)
found
in
today’s
high-speed digital electronic systems.
The devices use a Cypress proprietary phase-locked loop
(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 is greatly reduced.
This reduction in radiated energy can significantly reduce the
cost of complying with regulatory agency requirements and
improve time to market without degrading system perfor-
mance.
The input frequency range is 4 to 32 MHz and accepts clock,
crystal and ceramic resonator inputs. The output clock can be
selected to produce 1x, 2x, or 4x multiplication of the input
frequency with Spread Spectrum Frequency Modulation.
The use of 2x or 4x frequency multiplication eliminates the
need for higher order crystals and enables the user to
generate up to 128-MHz Spread Spectrum Clock (SSC) by
using only first order crystals. This will reduce the cost while
improving the system clock accuracy, performance and
complexity.
Center Spread or Down Spread frequency modulation can be
selected by the user based on four discrete values of
Spread % for each Spread Mode with the option of a
Non-Spread mode for system test and verification purposes.
The CY25811/12/14 products are available in an 8-pin SOIC
(150-mil.) package with a Commercial operating temperature
range of 0 to 70
°C and Industrial Temperature range of –40 to
85°C. Refer to CY25568 for multiple clock output options such
as modulated and unmodulated clock outputs or Power-down
function.
For
Automotive
applications,
refer
to
CY25811/12/14SE data sheet.
Input Frequency Range and Selection
The CY25811/12/14 input frequency range is 4 to 32 MHz.
This range is divided into three segments and controlled by
3-Level FRSEL pin as given in Table 1.
Spread% Selection
The CY25811/12/14 SSCG products provide Center-Spread,
Down-Spread and No-Spread functions. The amount of
Spread% is selected by using 3-Level S0 and S1 digital inputs
and Spread% values are given in Table 2.
Pin Definitions
Pin No.
Name
Type
Description
1Xin/CLK
Crystal, ceramic resonator or clock input pin.
2VSS
Power supply ground.
3S1
Digital Spread% control pin. 3-Level input (H-M-L). Default = M.
4S0
Digital Spread% control pin. 3-Level input (H-M-L). Default = M.
5
SSCLK
Spread Spectrum output clock.
6
FRSEL
Input frequency range selection digital control input. 3-Level input (H-M-L). Default = M.
7VDD
Positive power supply.
8XOUT
Crystal or ceramic resonator output pin.
Table 1. Input Frequency Selection
FRSEL
Input Frequency Range
0
4.0 to 8.0 MHz
1
8.0 to 16.0 MHz
M
16.0 to 32.0 MHz
Table 2. Spread% Selection
XIN
(MHz)
FRSEL
S1 = 0
S0 = 0
S1 = 0
S0 = M
S1 = 0
S0 = 1
S1 = M
S0 = 0
S1 = 1
S0 = 1
S1 = 1
S0 = 0
S1 = M
S0 = 1
S1 = 1
S0 = M
S1 = M
S0 = M
Center
(%)
Center
(%)
Center
(%)
Center
(%)
Down
(%)
Down
(%)
Down
(%)
Down
(%)
No Spread
4-5
0
±1.4
± 1.2
± 0.6
± 0.5
–3.0
–2.2
–1.9
–0.7
0
5-6
0
±1.3
± 1.1
± 0.5
± 0.4
–2.7
–1.9
–1.7
–0.6
0
6-7
0
±1.2
± 0.9
± 0.5
± 0.4
–2.5
–1.8
–1.5
–0.6
0
7-8
0
±1.1
± 0.9
± 0.4
± 0.3
–2.3
–1.7
–1.4
–0.5
0
8-10
1
±1.4
±1.2
± 0.6
± 0.5
–3.0
–2.2
–1.9
–0.7
0
10-12
1
±1.3
±1.1
± 0.5
± 0.4
–2.7
–1.9
–1.7
–0.6
0
12-14
1
±1.2
± 0.9
± 0.5
± 0.4
–2.5
–1.8
–1.5
–0.6
0
14-16
1
±1.1
± 0.9
± 0.4
± 0.3
–2.3
–1.7
–1.4
–0.5
0
16-20
M
±1.4
±1.2
± 0.6
± 0.5
–3.0
–2.2
–1.9
–0.7
0
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