Cypress CY25566 Spread spectrum clock generator Datasheet

CY25566
Spread Spectrum Clock Generator
Features
•
•
•
•
• Center spread modulation
• Low cycle-to cycle jitter
• 16-pin SOIC package
25- to 200-MHz operating frequency range
Wide range of spread selections (9)
Accepts clock or crystal inputs
Provides four clocks
— SSCLK1a
Applications
• High-resolution VGA controllers
• LCD panels and monitors
• Printers and MFPs
— SSCLK1b
— SSCLK2
Benefits
— REFOUT
• Low-power dissipation
— 3.3V = 70 mW (typical @ 40 MHz, no load)
• Peak EMI reduction by 8 to 16 dB
• Fast time to market
• Cost reduction
Pin Configuration
Block Diagram
REFOFF
2
3 REFOUT
Xin/
CLK
REFERENCE
DIVIDER
1
Xout 16
PD
MODULATION
CONTROL
VDD 4
FEEDBACK
DIVIDER
INPUT
DECODER
LOGIC
VSS 5
16
XOUT
2
15
SSCLK2
REFOUT
3
14
VSS
VDD
4
VSS
5
S2
6
11
S3
7
10 SSCC
SSCLK1a
8
9
13 S0
12 S1
VSS
SSCLK1b
8 SSCLK1a
9 SSCLK1b
VDD
20 K
1
REFOFF
vco
DIVIDER
&
MUX
VDD
VSS 11
Loop
Filter
CP
XIN/CLKIN
CY25566
300K
20 K
15 SSCLK2
/2
RANGE
CONTROL
VSS 14
20 K
20 K
VSS
10
SSCC
VSS
12
S1
13
6
7
S0
S2
S3
Cypress Semiconductor Corporation
Document #: 38-07429 Rev. *B
•
3901 North First Street
•
San Jose
•
CA 95134 • 408-943-2600
Revised October 26, 2005
CY25566
Pin Description
Pin
Name
Type
Description
1
XIN/CLKIN
I
Clock or Crystal connection input. Refer to Table 1, Table 2, and Table 3 for input
frequency range selection.
2
REFOFF
I
Input pin enables REFOUT clock at pin 3. REFOFF 400KΩ internal pull-up resistor.
Logic “0” enables REFOUT, logic “1” disables REFOUT. Default = disabled.
3
REFOUT
O
Buffered, non-modulated output clock derived from XIN/CLKIN input frequency.
There is a 180° phase shift from XIN to REFOUT.
4
VDD
P
Positive power supply. Bypass to ground with 0.1-µF capacitor.
5, 11, 14
VSS
G
Positive power supply ground.
6
S2
I
VCO range control. Refer to Table 1, Table 2, and Table 3 for detailed programming information. Has 400-KΩ internal pull-up to VDD.
7
S3
I
VCO range control. Refer to Table 1, Table 2, and Table 3 for detailed programming information. Has 400-KΩ internal pull-up to VDD.
8
SSCLK1a
O
Modulated clock output. Pins 8 and 9 are identical but separate drivers.
9
SSCLK1b
O
Modulated clock output. Pins 8 and 9 are identical but separate drivers.
10
SSCC
I
Spread Spectrum clock control (enable/disable) function. SSCG function is enabled
when input is high and disabled when input is low. Internal 400-KΩ pull-up defaults to
modulation ON.
12
S1
I
Tri-level logic input control pin used to select frequency and bandwidth.
Frequency/bandwidth selection and tri-level logic programming details. See Figure 2 and
Table 1, Table 2, and Table 3. Pin 8 has internal resistor divider network to VDD and VSS.
13
S0
I
Tri-level logic input control pin used to select frequency and bandwidth.
Frequency/bandwidth selection and tri-level logic programming details. See Figure 2 and
Table 1, Table 2, and Table 3. Pin 8 has internal resistor divider network to VDD and VSS.
15
SSCLK2
O
Modulated output clock. Frequency of SSCLK2 = SSCLK1a/2. BW% of SSCLK2 is equal
to BW% of SSCLK1a/b.
16
XOUT
O
Oscillator output pin connected to crystal. Leave this pin unconnected if an external
clock drives XIN/CLK.
General Description
S1. See Table 1, Table 2, and Table 3 for programming details
for S2 and S3.
The Cypress CY25566 is a Spread Spectrum Clock Generator
(SSCG) IC used for the purpose of reducing electromagnetic
interference (EMI) found in today’s high-speed digital
electronic systems.
The CY25566 will operate over a wide range of frequencies
from 25 to 200 MHz. Operation to 200 MHz is possible with the
use of dual drivers at pins 8 and 9. With a wide range of
selectable bandwidths, the CY25566 is a very flexible low-EMI
clock. Modulation can be disabled to provide a four-output
conventional clock.
The CY25566 uses a Cypress-proprietary phase-locked loop
(PLL) and Spread Spectrum Clock (SSC) technology to
synthesize and frequency modulate the input frequency of the
digital clock. By frequency modulating the clock, (SSCLK1a/b
and SSCLK2), the measured EMI at the fundamental and
harmonic frequencies is greatly reduced. The modulated
output frequency is centered on the input frequency.
Output Clock Architecture
This reduction in radiated energy can significantly reduce the
cost of complying with regulatory agency requirements and
improve time to market without degrading system performance.
The CY25566 provides four separate output clocks: REFOUT,
SSCLK1a, SSCLK1b, and SSCLK2 for use in a wide variety of
applications. Each clock output is described below in detail.
The CY25566 provides four output clocks: SSCLK1a,
SSCLK1b, SSCLK2, and REFOUT. SSCLK1a/b and SSCLK2
are modulated clocks and REFOUT is a buffered copy of the
reference clock or oscillator. The CY25566 frequency and
spread % ranges are selected by programming S0, S1, S2,
and S3 digital inputs. S0 and S1 use three (3) logic states
including High (H), Low (L), and Middle (M) to select one of
nine available frequency and spread % ranges. Refer to
Figure 2 for details on programming three level inputs S0 and
Document #: 38-07429 Rev. *B
The CY25566 is available in a 16-pin SOIC (150-mil.) package
with a commercial operating temperature range of 0°C to
70°C.
REFOUT
REFOUT is a 3.3V CMOS level non-modulated inverted copy
of the clock at XIN/CLKIN. As an inverted clock, the output
clock at REFOUT is 180° out of phase with the input clock at
XIN/CLKIN. Placing a high(1) logic state of REFOFF, pin 2, will
disable the REFOUT clock. When REFOUT is disabled,
REFOUT, pin 3 is at a low(0) logic state.
Page 2 of 9
CY25566
Control Logic Structures
SSCLK1a/b
SSCLK1a and SSCLK1b are spread spectrum clock outputs
used for the purpose of reducing EMI in digital systems.
SSCLK1a and SSCLK1b can be connected in several different
ways to provide flexibility in application designs. Each clock
can drive separate nets with a capacitative load up to 15 pF
each or connected together to provide drive to a single net with
a capacitative load as high as 33 pF. When both clocks are
connected together, the CY25566 is capable of driving 3.3V
CMOS-compatible clocks to frequencies as high as 200 MHz.
If one clock output is not connected to a load, negligible EMI
will be generated at the unused pin because there is no current
being driven. The frequency and bandwidth of SSCLK1a and
SSCLK1b is programmed by the logic states presented to S2
and S3. The frequency multiplication at SSCLK1a and
SSCLK1b is either 1X or 2X, controlled by S2 and S3. The
modulated output clock SSCLK1 is provided at pins 8 and 9
with each pin having separate but identical drivers. Refer to
Figure 1 below.
C Y 25566
9
8
The CY25566 has six input control pins for programming VCO
range, BW %, Mod ON/OFF and REFOUT ON/OFF. These
programmable control pins are described below.
REFOFF
The output clock REFOUT can be enabled or disabled by
controlling the state of REFOFF. When REFOFF is at a logic
low(0) state, REFOUT is enabled and the reference clock
frequency is present at pin 3. When REFOFF is at a logic high
state (1), REFOUT is disabled and is set to a logic low state
on pin 3. REFOFF has a 400-KW internal pull-up resistor to
VDD.
S0 and S1 (Tri-level Inputs)
S0 and S1 are used to program the frequency range and
bandwidth of the modulated output clocks SSCLK1a/b and
SSCLK2. S0 and S1 of the CY25566 are designed to sense
three different analog levels. With this tri-level structure, the
CY25566 is able to detect 9 different logic states. Refer to
tables 5, 6 and 7 for the results of each of these 9 states. The
level of each state is defined as follows:
Logic State “0” is a voltage that is between 0 and 0.15 × VDDV.
3 3 p f.
Logic State “M” is a voltage between 0.4 × VDD and 0.6 × VDDV.
Logic State “1” is a voltage between 0.85 × VDD and VDD.
Figure 2 illustrates how to program tri-level logic.
C Y 25566
9
S2 and S3
1 5 p f.
S2 and S3 are used to program the CY25566 into different
frequency ranges and multipliers. The CY25566 operates over
a frequency range of 25 to 200 MHz and a 1X or 2X multiplication of the reference frequency. S2 and S3 are binary logic
inputs and each has a 400 K W pull-up resistor to VDD. See
Table 1, Table 2, and Table 3 for programming details.
8
1 5 p f.
Figure 1. SSCLK1a/b Driver Configurations
SSCLK2
SCLK2 is a Spread Spectrum Clock with a frequency half that
of the SSCLK1a clock frequency. When SSCLK1a is
programmed to provide a 2.5% modulated clock at 1X times
the reference clock, 40 MHz for example, the frequency of
SSCLK2 will be 20 MHz with a BW of 2.5%. Note that by
programming the frequency of SSCLK1a to 2X, the frequency
of SSCLK2 will be 1X times the reference clock frequency.
SSCC is an input control pin that enables or disables SSCG
modulation of the output clock at SSCLK1a/b and SSCLK2.
Disabling modulation is a method of comparing radiated EMI
in a product with SSCG turned on or off.
The CY25566 can be used as a conventional low jitter multiple
output clock when SSCC is set to low (0). SSCC has a 400-KW
internal pull-up resistor. Logic high (1) = Modulation ON, logic
low (0) = Modulation OFF. Default is modulation ON.
VDD
CY25566
CY25566
S0 = "M" (N/C)
SSCC
S0
13
S1 = "0" (GND) 12
S0
S0 = "1"
13
10
S0
S0 = "1"
13
S1 = "1"
12
SSCC = "1"
10
S1
S1
S1 = "0" (GND)
12
SSCC = "1"
10
VDD
SSCC = "1"
VDD
CY25566
S1
VDD
Figure 2.
Document #: 38-07429 Rev. *B
Page 3 of 9
CY25566
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.
Modulation Rates of SSCG clocks are generally referred to in
terms of frequency or Fmod = 1/Tmod.
The input clock frequency, Fin, and the internal divider count,
Cdiv, determine the Modulation Rate. The CY25566 utilizes
two different modulation rate dividers, depending on the range
selected on S2 and S3 digital control inputs. Refer to the
example below.
S3, S2
CDiv
Output Frequency
0,0
1166
1X
0,1
1166
2X
1,0
2332
1X
1,1
N/A
N/A
The CY25566 has three frequency groups to select from. Each
combination of frequency and bandwidth can be selected by
programming the input control lines, S0–S3, to the proper logic
state.
Group 1 is the 1X low-frequency range and operates from 25
to 100 MHz.
Group 2 is the 1X high-frequency range and operates from 50
to 200 MHz.
Group 3 is the 2X low frequency range and operates from 25
to 50 MHz and 50 to 100 MHz output.
Example:
Device = CY25566
Fin = 65 MHz
Range = S3 = 0, S2 = 1, S0 = 0
Then: modulation rate = Fmod = 65 MHz/1166 = 55.7 kHz
Modulation Profile
Spectrum Analyzer
Figure 3. SSCG Clock, CY25566, 65 MHz
Document #: 38-07429 Rev. *B
Page 4 of 9
CY25566
Table 1. Frequency and Bandwidth Selection Chart (Group 1)(Low Frequency (1x) Selection Chart)
25–50 MHz (Low Range)
XIN/CLK
(MHz)
S1 = M
S0 = M
S1 = M
S0 = 0
S1 = 1
S0 = 0
S1 = 0
S0 = 0
S1 = 0
S0 = M
25–35
4.3
3.8
3.4
2.9
2.8
35–40
3.9
3.5
3.1
2.5
2.4
40–45
3.7
3.3
2.8
2.4
2.3
45–50
3.4
3.1
2.6
2.2
2.1
S3 S2
0
0
50–100 MHz (High Range)
XIN/CLK
(MHz)
S1 = 1
S0 = M
S1 = 0
S0 = 1
S1 = 1
S0 = 1
S1 = M
S0 = 1
50–60
2.9
2.1
1.5
1.2
60–70
2.8
2.0
1.4
1.1
70–80
2.6
1.8
1.3
1.1
80–100
2.4
1.7
1.2
1.0
S3 S2
0
0
Table 2. Frequency and Bandwidth Selection Chart (Group 2)(High Frequency (1x) Selection Chart)
50–100 MHz (Low Range)
XIN/CLK
(MHz)
S1 = M
S0 = M
S1 = M
S0 =0
S1 = 1
S0 = 0
S1 = 0
S0 = 0
S1 = 0
S0 = M
50–60
4.2
3.8
3.2
2.8
2.7
60–70
4.0
3.6
3.1
2.6
2.5
70–80
3.8
3.4
2.9
2.5
2.4
80–100
3.5
3.1
2.7
2.2
2.1
100–200 MHz (High Range)
XIN/CLK
(MHz)
S1 = 1
S0 = M
S1 = 0
S0 = 1
S1 = 1
S0 = 1
S1 = M
S0 = 1
100–120
3.0
2.4
1.6
1.3
120–130
2.7
2.1
1.4
1.1
130–140
2.6
2.0
1.3
1.1
140–150
2.6
2.0
1.3
1.1
150–160
2.5
1.8
1.2
1.0
160–170
2.4
1.8
1.2
1.0
170–180
2.4
1.8
1.2
1.0
180–190
2.3
1.7
1.1
0.9
190–200
2.3
1.6
1.1
0.9
S3 S2
1
0
S3 S2
1
0
Table 3. Frequency and Bandwidth Selection Chart (Group 3)(Low Frequency (2x) Selection Chart)
25–50 MHz (Low Range, 2X)
XIN/CLK
(MHz)
SSCLK1
(MHz)
S1 = M
S0 = M
S1 = M
S0 = 0
S1 = 1
S0 = 0
S1 = 0
S0 = 0
S1 = 0
S0 = M
25–35
50-70
4.0
3.5
3.0
2.6
2.5
35–40
70-80
3.8
3.3
2.9
2.4
2.3
40–45
80-90
3.5
3.1
2.7
2.2
2.1
45–50
90-100
3.3
2.9
2.5
2.1
2.0
Document #: 38-07429 Rev. *B
S3 S2
0
1
Page 5 of 9
CY25566
Application Schematic
In this example, the CY25566 is being driven by a 75-MHz
reference clock.
VDD = 3.30 VDC.
S0 = 0 and S1 = 0 are programmed to select a BW of 2.5%.
(Refer to Table 1 and 2.)
SSCLK1b = 75 MHz @ 2.5% center spread modulation.
S2 = 0 and S3 = 1 are programmed to select the Group 2
range.
REFOUT = 37.5 MHz non-modulated clock.
SSCLK1a = 75 MHz @ 2.5% center spread modulation.
SSCLK 2 = 37.5 MHz @ 2.5% center spread modulation.
VDD
0.1 uF
75 MHz Clock source
4
1
XIN/CLKIN VDD
REFOUT
3
REFOUT
16
XOUT
SSCLK2
15
SSCLK2
CY25566
2
REFOFF
VDD
10
7
6
12
13
SSCLK1a
8
SSCLK1a
SSCC
S3
S2
S1
S0
SSCLK1b
VSS
5
VSS
11
9
SSCLK1b
VSS
14
Figure 4. Application Schematic
Document #: 38-07429 Rev. *B
Page 6 of 9
CY25566
Absolute Maximum Ratings[1, 2]
Supply Voltage (VDD: .......................................................+6V
Operating Temperature: ...................................... 0°C to 70°C
Storage Temperature .................................. –65°C to +150°C
Table 4. DC Electrical Characteristics VDD = 3.3V, Temp. = 25°C, unless otherwise noted
Parameter
Description
VDD
Power Supply Range
Conditions
±10%
Min.
Typ.
Max.
Unit
2.97
3.3
3.63
V
VINH
Input High Voltage
S0 and S1 only.
0.85VDD
VDD
VDD
V
VINM
Input Middle Voltage
S0 and S1 only.
0.40VDD
0.50VDD
0.60VDD
V
VINL
Input Low Voltage
S0 and S1 only.
0.0
0.0
0.15VDD
V
VOH1
Output High Voltage
IOH = 6 ma, SSCLKa
2.4
VOH2
Output High Voltage
IOH = 20 ma, SSCLKb
2.0
VOL1
Output Low Voltage
IOH = 6 ma, SSCLKa
VOL2
Output Low Voltage
IOH = 20 ma, SSCLKb
1.2
V
Cin1
Input Capacitance
Xin/CLK (Pin 1)
3
4
5
pF
Cin2
Input Capacitance
Xout (Pin 8)
6
8
10
pF
Cin2
Input Capacitance
All input pins except 1.
3
4
5
pF
IDD1
Power Supply Current
FIN = 40 MHz,15 pF@all outputs
27
32
mA
IDD1
Power Supply Current
FIN = 40 MHz, No Load
21
28
mA
IDD2
Power Supply Current
FIN = 165 MHz,15 pF@all outputs
68
80
mA
IDD2
Power Supply Current
FIN = 165 MHz, No Load
48
60
mA
V
V
0.4
V
Table 5. Electrical Timing Characteristics VDD = 3.3V, T = 25°C and CL = 15 pF, unless otherwise noted. Rise/Fall @ 0.4–2.4V,
[email protected]
Parameter
Description
Conditions
Min.
Typ.
Max
Unit
ICLKFR
Input Clock Frequency Range Non-crystal, 3.0V Pk–Pk ext. source
25
200
MHz
tRISE(a)
Clock Rise Time
SSCLK1a or SSCLK1b, Freq = 100 MHz
1.0
1.3
1.6
ns
tFALL(a)
Clock Fall Time
SSCLK1a or SSCLK1b, Freq = 100 MHz
1.0
1.3
1.6
ns
tRISE(a+b)
Clock Rise Time
SSCLK1(a+b), CL = 33 pF, 100 MHz
1.2
1.5
1.8
ns
tFALL(a+b)
Clock Fall Time
SSCLK1(a+b), CL = 33 pF, 100 MHz
1.2
1.5
1.8
ns
tRISE(a+b)
Clock Rise Time
SSCLK1(a+b), CL = 33 pF, 200 MHz
1.1
1.4
1.7
ns
tFALL(a+b)
Clock Fall Time
SSCLK1(a+b), CL = 33 pF, 200 MHz
1.1
1.4
1.7
ns
tRISE(REF)
Clock Rise Time
REFOUT, Pin 3, CL = 15 pF, 50 MHz
1.0
1.3
1.6
ns
tFALL(REF)
Clock Fall Time
REFOUT, Pin 3, CL = 15 pF, 50 MHz
1.0
1.3
1.6
ns
DTYin
Input Clock Duty Cycle
XIN/CLK (Pin)
30
50
70
%
DTYout
Output Clock Duty Cycle
SSCLK1a/b (Pin 8 and 9)
45
CCJ1
Cycle-to-Cycle Jitter
F = 100 MHz, SSCLK1a/b CL = 33 pF
CCJ2
Cycle-to-Cycle Jitter
F = 200 MHz, SSCLK1a/b CL = 33 pF
REFOUT
Refout Frequency Range
CL = 15 pF
25
50
55
%
300
400
ps
500
600
ps
108
MHz
Note:
1. Operation at any Absolute Maximum Rating is not implied.
2. Single Power Supply: The voltage on any input or I/O pin cannot exceed the power pin during power-up.
Document #: 38-07429 Rev. *B
Page 7 of 9
CY25566
Ordering Information
Part Number
Package Type
Product Flow
CY25566SC
16-pin SOIC
Commercial, 0° to 70°C
CY25566SCT
16-pin SOIC–Tape and Reel
Commercial, 0° to 70°C
Package Drawing and Dimensions
16-Lead (150-Mil) SOIC S16.15
16 Lead (150 Mil) SOIC
PIN 1 ID
8
1
DIMENSIONS IN INCHES[MM] MIN.
MAX.
REFERENCE JEDEC MS-012
PACKAGE WEIGHT 0.15gms
0.150[3.810]
0.157[3.987]
0.230[5.842]
0.244[6.197]
PART #
S16.15 STANDARD PKG.
SZ16.15 LEAD FREE PKG.
9
16
0.386[9.804]
0.393[9.982]
0.010[0.254]
0.016[0.406]
SEATING PLANE
X 45°
0.061[1.549]
0.068[1.727]
0.004[0.102]
0.050[1.270]
BSC
0°~8°
0.0138[0.350]
0.0192[0.487]
0.004[0.102]
0.0098[0.249]
0.016[0.406]
0.035[0.889]
0.0075[0.190]
0.0098[0.249]
51-85068-*B
All product and company names mentioned in this document are the trademarks of their respective holders.
Document #: 38-07429 Rev. *B
Page 8 of 9
© Cypress Semiconductor Corporation, 2002. 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 Semiconductor product. Nor does it convey or imply any license under patent or other rights. Cypress Semiconductor 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
Semiconductor products in life-support systems application implies that the manufacturer assumes all risk of such use and in doing so indemnifies Cypress Semiconductor against all charges.
CY25566
Document Title:CY25566 Spread Spectrum Clock Generator
Document Number: 38-07429
Rev.
ECN No.
Issue
Date
Orig. of
Change
**
115771
07/01/02
OXC
New Data Sheet
*A
122705
12/30/02
RBI
Added power up requirements to maximum ratings information.
*B
404070
See ECN
RGL
Minor Change: Typo error on table 1, column 2 , S0 = 0 (not M)
Document #: 38-07429 Rev. *B
Description of Change
Page 9 of 9