Cypress Semiconductor CY25818 Manuale utente
Spread Spectrum Clock Generato
r
CY25818/19
Cypress Semiconductor Corporation • 198ChampionCourt • San Jose,CA 95134-1709 • 408-943-2600
Document #: 38-07362 Rev. *B Revised April 11, 2006
Features
• 8- to 32-MHz input frequency range
• CY25818: 8–16 MHz
• CY25819: 16–32 MHz
• Separate modulated and unmodulated clocks
• Accepts clock, crystal, and resonator inputs
• Down spread modulation
• Power-down function
• Low-power dissipation
— CY25818 = 33 mW-typ @ 8 MHz
— CY25818 = 56 mW-typ @ 16 MHz
— CY25819 = 36 mW-typ @ 16 MHz
— CY25819 = 63 mW-typ @ 32 MHz
• Low cycle-to-cycle jitter
— SSCLK = 250 ps-typ
— REFOUT = 275 ps-typ
• Available in 8-pin (150-mil) SOIC package
Applications
• Printers and MFPs
• LCD panels and notebook PCs
• Digital copiers
•PDAs
• Automotive
• CD-ROM, VCD, and DVD
• Networking and LAN/WAN
•Scanners
•Modems
• Embedded digital systems
Benefits
• Peak electromagnetic interference (EMI) reduction by
8–16 dB
• Fast time to market
• Cost reduction
REFERENCE
DIVIDER PD and
CP LF
VCO
DIVIDER
and
MUX
INPUT
DECODER
1
8
300K
MODULATION
CONTROL
3 6
S0 PD#
XIN/CLKIN
XOUT
VDD 7
VSS 2
4SSCLK
5REFCLK
VCO
COUNTER
2
1
3
4
8
7
6
5
XIN/CLKIN
Vss
S0
SSCLK
XOUT
Vdd
PD#
REFCLK
CY25818
CY25819
8 Pin SOIC
8-pin SOIC
Block Diagram Pin Configuration
[+] Feedback
CY25818/19
Document #: 38-07362 Rev. *B Page 2 of 7
.
Overview
The Cypress CY25818/19 products are Spread Spectrum
Clock Generator (SSCG) ICs used for the purpose of reducing
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 8–16 MHz for the CY25818 and
16–32 MHz for the CY25819. Both products accept external
clock, crystal, or ceramic resonator inputs.
The CY25818/19 provide separate modulated (SSCLK) and
unmodulated reference (REFCLK) clock outputs which are the
same frequency as the input clock frequency. Down spread
frequency modulation can be selected by the user, based on
three discrete values of Spread%. A separate power down
function is also provided.
The CY25818/19 products are available in an 8-pin SOIC
(150-mil) package with a commercial operating temperature
range of 0–70°C. Contact Cypress for availability of –40 to
+85°C industrial temperature range operation or TSSOP
package versions. Refer to the CY25568, CY25811,
CY25812, and CY25814 products for other functions such as
clock multiplication of 1×, 2×, or 4× to generate a wide range
of Spread Spectrum output clocks from 4 to 128 MHz.
Input Frequency Range and Selection
CY25818/19 input frequency range is 8–32 MHz. This range
is divided into two segments, as given in Table 1.
Spread% Selection
CY25818/19 SSCG products provide Down-Spread frequency
modulation. The amount of Spread% is selected by using
3-Level S0 digital input. Spread% values are given in Table 2.
Pin Description
Pin Name Description
1 XIN/CLK Clock, Crystal, or Ceramic Resonator Input Pin.
2 Vss Power Supply Ground.
3 S0 Digital Spread% Control Pin. 3-Level input (H-M-L). Default = M.
4 SSCLK Modulated Spread Spectrum Output Clock. The output frequency is referenced to input frequency. Refer
to Table 2 for the amount of modulation (Spread%).
5REFCLK
Unmodulated Reference Clock Output. The unmodulated output frequency is the same as the input
frequency.
6 PD# Power-Down Control Pin. Default = H (Vdd).
7 Vdd Positive Power Supply.
8XOUT
Clock, Crystal, or Ceramic Resonator Output Pin. Leave this pin unconnected if an external clock is used
at XIN pin.
Table 1. Input and Output Frequency Selection
Product Input/Output Frequency Range
CY25818 8–16 MHz
CY25819 16–32 MHz
Table 2. Spread% Selection
XIN (MHz) Product S0 = 1 S0 = 0 S0 = M
Down (%) Down (%) Down (%)
8–10 CY25818 –3.0 –2.2 –0.7
10–12 CY25818 –2.7 –1.9 –0.6
12–14 CY25818 –2.5 –1.8 –0.6
14–16 CY25818 –2.3 –1.7 –0.5
16–20 CY25819 –3.0 –2.2 –0.7
20–24 CY25819 –2.7 –1.9 –0.6
24–28 CY25819 –2.5 –1.8 –0.6
28–32 CY25819 –2.3 –1.7 –0.5
[+] Feedback
CY25818/19
Document #: 38-07362 Rev. *B Page 3 of 7
3-Level Digital Inputs
S0 digital input is designed to sense three logic levels desig-
nated as HIGH “1,” LOW “0,” and MIDDLE “M.” With this
3-Level digital input logic, the 3-Level logic is able to detect
three different logic levels.
The S0 pin includes an on-chip 20K (10K/10K) resistor divider.
No external application resistors are needed to implement
3-Level logic, as follows.
Logic Level “0”: 3-Level logic pin connected to GND.
Logic Level “M”: 3-Level logic pin left floating (no connection.)
Logic Level “1”: 3-Level logic pin connected to Vdd.
Figure 1 illustrates how to implement 3-Level Logic.
Modulation Rate
Spread Spectrum Clock Generators utilize frequency
modulation (FM) to distribute energy over a specific band of
frequencies. The maximum frequency of the clock (fmax) and
minimum frequency of the clock (fmin) determine this band of
frequencies. The time required to transition from fmin to fmax
and back to fmin is the period of the Modulation Rate, Tmod.
The Modulation Rates of SSCG clocks are generally referred
to in terms of frequency, and fmod = 1/Tmod.
The input clock frequency, fin, and the internal divider
determine the Modulation Rate.
In the case of CY25818/19 devices, the (Spread Spectrum)
Modulation Rate, fmod, is given by the following formula:
fmod = fIN/DR
where fmod is the Modulation Rate, fIN is the Input Frequency,
and DR is the Divider Ratio, as given in Table 3.
Maximum Ratings[1, 2]
Supply Voltage (Vdd): ..................................................+ 5.5V
Input Voltage Relative to Vdd:..............................Vdd + 0.3V
Input Voltage Relative to Vss:...............................Vss + 0.3V
Operating Temperature:................................... 0°C to + 70°C
Storage Temperature:................................ –65°C to + 150°C
LOGIC
LOW (0) LOGIC
MIDDLE (M) LOGIC
HIGH (H)
S0
to VDD
S0
UNCONNECTED
S0
to VSS
VDD
VSS Figure 1. 3-Level Logic
Table 3. Modulation Rate Divider Ratios
Product Input Frequency Range Divider Ratio (DR)
CY25818 8–16 MHz 256
CY25819 16–32 MHz 512
Table 4. DC Electrical Characteristics Vdd = 3.3V ±10%, TA= 0°C to +70°C and CL = 15 pF (unless otherwise noted)
Parameter Description Conditions Min. Typ. Max. Unit
Vdd Power Supply Range 2.97 3.3 3.63 V
VINH Input HIGH Voltage S0 Input 0.85 Vdd Vdd Vdd V
VINM Input MIDDLE Voltage S0 Input 0.40 Vdd 0.50 Vdd 0.60 Vdd V
VINL Input LOW Voltage S0 Input 0.0 0.0 0.15 Vdd V
VOH1 Output HIGH Voltage IOH = 4 ma, SSCLK and REFCLK 2.4 – – V
VOH2 Output HIGH Voltage IOH = 6 ma, SSCLK and REFCLK 2.0 – – V
VOL1 Output LOW Voltage IOL = 4 ma, SSCLK Output – – 0.4 V
VOL2 Output LOW Voltage IOL = 10 ma, SSCLK Output – – 1.2 V
CIN1 Input Capacitance XIN (Pin 1) and XOUT (Pin 8) 6.0 7.5 9.0 pF
CIN2 Input Capacitance All Digital Inputs 3.5 4.5 6.0 pF
IDD1 Power Supply Current FIN=8 MHz, no load – 10.0 12.5 mA
IDD3 Power Supply Current FIN=32 MHz, no load – 19.0 23.0 mA
IDD4 Power Supply Current PD# = Vss – 150 250 mA
[+] Feedback
CY25818/19
Document #: 38-07362 Rev. *B Page 4 of 7
Characteristics Curves
The following curves demonstrate the characteristic behavior
of the CY25818/19 when tested over a number of environ-
mental and application specific parameters. These are typical
performance curves and are not meant to replace any
parameter specified in Table 4 and Table 5.
Notes:
1. Single Power Supply: The voltage on any input or I/O pin cannot exceed the power pin during power-up.
2. Operation at any Absolute Maximum Rating is not implied.
Table 5. Timing Electrical Characteristics Vdd = 3.3V ±10%, TA= 0°C to +70°C and CL= 15 pF (unless otherwise noted)
Parameter Description Conditions Min. Typ. Max. Unit
ICLKFR1 Input Frequency Range CY25818 8 – 16 MHz
ICLKFR2 Input Frequency Range CY25819 16 – 32 MHz
trise1 Clock Rise Time SSCLK and REFCLK, 0.4V to 2.4V 2.0 3.0 4.0 ns
tfall1 Clock Fall Time SSCLK and REFCLK, 0.4V to 2.4V 2.0 3.0 4.0 ns
CDCin Input Clock Duty Cycle XIN 20 50 80 %
CDCout Output Clock Duty Cycle SSCLK and REFCLK @ 1.5V 45 50 55 %
CCJss Cycle-to-Cycle Jitter SSCLK; FIN = FOUT = 8–32 MHz 250 350 ps
CCJref Cycle-to-Cycle Jitter REFCLK; FIN = FOUT = 8–32 MHz 275 375 ps
200
210
220
230
240
250
260
270
280
290
300
8 121620242832
Frequency (MHz)
CCJ (ps)
REFCLK CY25818
SSCLK CY25818
REFCLK CY25819
SSCLK CY25819
Figure 2. CCJ (ps) vs. Frequency (MHz)
1.75
2
2.25
2.5
2.75
-40 -25 -10 5 20 35 50 65 80 95 110 125
Temp (C)
BW %
12 MHz
32.0MHz
Figure 3. Bandwidth% vs. Temperature
10
11
12
13
14
15
16
17
18
19
20
8 121620242832
Frequency (MHz)
IDD(mA
)
CY25819
16 - 32 MHz
CY25818
8 - 16 MHz
Figure 4. IDD (mA) vs. Frequency (MHz)
1.8
1.9
2
2.1
2.2
2.3
2.4
2.5
2.6
2.7
2.8
2.9
3
3.1
2.8 2.9 3 3.1 3.2 3.3 3.4 3.5 3.6 3.7
VDD (volts)
BW (%)
CY25819@32 MHz
CY25818@8.0 MHz
Figure 5. Bandwidth% vs. Vdd
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CY25818/19
Document #: 38-07362 Rev. *B Page 5 of 7
SSCG Profiles
CY25818/19 SSCG products use a non-linear “optimized”
frequency profile as shown in Figure 6 and Figure 7. The use
of Cypress proprietary “optimized” frequency profile maintains
flat energy distribution over the fundamental and higher order
harmonics. This results in additional EMI reduction in
electronic systems.
Application Schematic
Notes:
3. XIN = 16.0 MHz; S0 = 1; SSCLK = 16.0 MHz; BW = –2.14%.
4. Xin = 32.0MHz; S0 = 1; SSCLK = 32.0 MHz; BW = -2.15%
Figure 6. CY25818Spread Spectrum Profile
(Frequency vs. Time)[3]
Figure 7. CY25819 Spread Spectrum Profile
(Frequency vs. Time)[4]
Vdd
1
8
14.3 MHz
or
27.0 MHz
Vss S0
XIN
XOUT
SSCLK
Vdd
CY25818
CY25819
3
4
0.1 uF
C3
C2
C3
27 pF
27 pF
14.3 MHz (CY25818)
27.0 MHz (CY25819)
REFCLK 5
2
7
PD#
6
Figure 8. Typical Application Schematic
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CY25818/19
Document #: 38-07362 Rev. *B Page 6 of 7
© Cypress Semiconductor Corporation, 2006. The information contained herein is subject to change without notice. Cypress Semiconductor Corporation assumes no responsibility for the use
of any circuitry other than circuitry embodied in a Cypress product. Nor does it convey or imply any license under patent or other rights. Cypress products are not warranted nor intended to be
used for medical, life support, life saving, critical control or safety applications, unless pursuant to an express written agreement with Cypress. Furthermore, Cypress does not authorize its
products for use as critical components in life-support systems where a malfunction or failure may reasonably be expected to result in significant injury to the user. The inclusion of Cypress
products in life-support systems application implies that the manufacturer assumes all risk of such use and in doing so indemnifies Cypress against all charges.
Package Drawing and Dimensions
All product and company names mentioned in this document may be the trademarks of their respective holders.
Ordering Information
Part Number Package Type Product Flow
CY25818SC 8-pin SOIC Commercial, 0°to 70°C
CY25818SCT 8-pin SOIC–Tape and Reel Commercial, 0°to 70°C
CY25819SC 8-pin SOIC Commercial, 0°to 70°C
CY25819SCT 8-pin SOIC–Tape and Reel Commercial, 0°to 70°C
Lead-free
CY25818SXC 8-pin SOIC Commercial, 0°to 70°C
CY25818SXCT 8-pin SOIC–Tape and Reel Commercial, 0°to 70°C
CY25819SXC 8-pin SOIC Commercial, 0°to 70°C
CY25819SXCT 8-pin SOIC–Tape and Reel Commercial, 0°to 70°C
SEATING PLANE
PIN1ID
0.230[5.842]
0.244[6.197]
0.157[3.987]
0.150[3.810]
0.189[4.800]
0.196[4.978]
0.050[1.270]
BSC
0.061[1.549]
0.068[1.727]
0.004[0.102]
0.0098[0.249]
0.0138[0.350]
0.0192[0.487]
0.016[0.406]
0.035[0.889]
0.0075[0.190]
0.0098[0.249]
1. DIMENSIONS IN INCHES[MM] MIN.
MAX.
0°~8°
0.016[0.406]
0.010[0.254] X 45°
2. PIN1IDISOPTIONAL,
ROUND ON SINGLE LEADFRAME
RECTANGULAR ON MATRIX LEADFRAME
0.004[0.102]
8 Lead (150 Mil) SOIC - S08
14
58
3. REFERENCE JEDEC MS-012
PART #
S08.15 STANDARD PKG.
SZ08.15 LEAD FREE PKG.
4. PACKAGE WEIGHT 0.07gms
8-lead (150-Mil) SOIC S8
51-85066-*C
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CY25818/19
Document #: 38-07362 Rev. *B Page 7 of 7
Document History Page
Document Title: CY25818/19 Spread Spectrum Clock Generator
Document Number: 38-07362
REV. ECN NO. Issue
Date Orig. of
Change Description of Change
** 112462 03/21/02 OXC New Data Sheet
*A 122701 12/28/02 RBI Added power up requirements to maximum rating information.
*B 448097 See ECN RGL Add Lead-free devices
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