APPROVED PRODUCT
FS781/82/84
LOW EMI SPECTRUM SPREAD CLOCK
Features
•
•
•
•
•
•
•
•
•
Spread Spectrum Clock Generator (SSCG)
with 1x, 2x and 4x Outputs
6 to 82 MHz operating frequency range.
Modulates external clocks including crystals,
crystal oscillators and ceramic resonators.
Programmable modulation with simple
R-C external loop filter (LF)
Center Spread Modulation.
3 - 5 Volt power supply.
TTL/CMOS compatible outputs.
Low short term jitter.
Low Power Dissipation;
3.3 VDC = 37 mw - typical
5.0 VDC = 115 mw - typical
•
Available in 8 pin SOIC and TSSOP
packages.
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Desktop/Notebook Computers
Printers, Copiers and MFP
Scanners and Fax
LCD Displays and Monitors
CD-ROM, VCD and DVD
Automotive and Embedded Systems
Networking, LAN/WAN
Digital Cameras and Camcorders
Modems
Benefits
•
•
•
•
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Programmable EMI Reduction
Fast Time to Market
Lower cost of compliance
No degradation in Rise/Fall times
Lower component and PCB layer count
Applications
Product Description
The Cypress FS781/2/4
are Spread Spectrum Clock Generator ICs (SSCG) designed for the purpose of reducing
Electro Magnetic Interference (EMI) found in today’s high-speed digital systems.
The FS781/2/4 SSCG
clocks use an IMI proprietary technology to modulate the input clock frequency, FS
OUT
by
modulating the frequency of the digital clock. By modulating the reference clock the measured EMI at the
fundamental and harmonic frequencies of FSOUT is greatly reduced. This reduction in radiated energy can
significantly reduce the cost of complying with regulatory requirements without degrading digital waveforms.
The Cypress FS781/2/4
clocks are very simple and versatile devices to use. By programming the two range
select lines, S0 and S1, any frequency from 6 to 82 MHz operating range can be selected. The FS781/2/4 are
designed to operate over a very wide range of input frequencies and provides 1x, 2x and 4x modulated clock
outputs.
The FS78x devices
have a simple frequency selection table that allows operation from 6 MHz to 82 MHz in four
separate ranges. The bandwidth of the frequency spread at FSOUT is determined by the values of the loop filter
components. The modulation rate is determined internally by the input frequency and the selected input frequency
range.
The Bandwidth
of these products can be programmed from as little as 0.6% up to as much as 4.0% by selecting
the proper loop filter value. Refer to the Loop Filter Selection chart on page 6 for recommended values. Due to a
wide range of application requirements, an external loop filter (LF) is used on the FS78x products. The user can
select the exact amount of frequency modulation suitable for the application. Using a fix internal loop filter would
severely limit the use of a wide range of modulation bandwidths (Spread %) to a few discrete values.
Refer to FS791/2/4 products for applications requiring 80 to 140 MHz frequency range.
Cypress Semiconductor Corporation
525 Los Coches St.
Milpitas, CA 95035. Tel: 408-263-6300, Fax: 408-263-6571
http://www.cypress.com
Document#: 38-07029 Rev. **
05/07/2001
Page 1 of 13
APPROVED PRODUCT
FS781/82/84
LOW EMI SPECTRUM SPREAD CLOCK
Block Diagram
Loop Filter
4(6)
250 K
Xin
1(3)
Reference
Divider
8 pF
Phase
Detector
VCO
10 pF.
Xout
Modulation
Control
2(4)
8 pF
VCO / N
VDD
8(2)
Power Contol
Logic
VDD Input Control Logic
Output
Divider
and
Mux
VSS
6(8)
FSOUT
5(7)
3(5)
7(1)
(TSSOP Pin #)
VSS
S1
S0
Figure 1. Block Diagram
Ordering Information
Product Number
FS781BZB
FS782BZB
FS784BZB
FS781BT
FS781BT
FS781BT
Marking Example:
FM-OUT Scaling
1xFin
2xFin
4xFin
1xFin
2xFin
4xFin
Date Code
FS781BZB
Lot Number
Package Type
8 Pin 150 mil SOIC
8 Pin 150 mil SOIC
8 Pin 150 mil SOIC
8 Pin 169 mil TSSOP
8 Pin 169 mil TSSOP
8 Pin 169 mil TSSOP
Production Flow
Commercial, 0 to 70°C
Commercial, 0 to 70°C
Commercial, 0 to 70°C
Commercial, 0 to 70°C
Commercial, 0 to 70°C
Commercial, 0 to 70°C
FS78xBZB
Flow
(“B” Flow not indicated on TSSOP package)
Packages
Z = SOIC (150 Mil)
T = TSSOP (169 Mil)
Revisions
Device Number
Cypress Semiconductor Corporation
525 Los Coches St.
Milpitas, CA 95035. Tel: 408-263-6300, Fax: 408-263-6571
http://www.cypress.com
Document#: 38-07029 Rev. **
05/07/2001
Page 2 of 13
APPROVED PRODUCT
FS781/82/84
LOW EMI SPECTRUM SPREAD CLOCK
Pin Configuration
Xin
Xout
S1
LF
1
2
3
4
FS78x
8
7
6
5
VDD
S0
FSOUT
VSS
S0
VDD
Xin
Xout
1
2
3
4
FS78x
8
7
6
5
FSOUT
VSS
LF
S1
8 Pin SOIC Package
8 Pin TSSOP Package
Pin Description
Pin No.
1/2
Pin Name
Xin / Xout
I/O
I/O
TYPE
Analog
Description
Pins form an on-chip reference oscillator when connected to
terminals of an external parallel resonant crystal. Xin may be
connected to TTL/CMOS external clock source. If Xin connected
to external clock other than crystal, leave Xout (pin 2)
unconnected.
Digital control inputs to select input frequency range and output
frequency scaling. Refer to Tables 7 & 8 for selection. S0 has
internal pulldown. S1 has internal pullup.
Loop Filter. Single ended tri-state output of the phase detector. A
two-pole passive loop filter is connected to Loop Filter (LF).
Modulated Clock Frequency Output. The center frequency is the
same as the input reference frequency for FS781. Input
frequency is multiplied by 2x and 4x for FS782 and FS784
respectively.
Positive Power Supply.
Power Supply Ground
Table 1
7/3
S0 / S1
I
CMOS/TTL
4
6
LF
FSOUT
I
O
Analog
CMOS/TTL
8
5
VDD
VSS
P
P
Power
Power
Output Frequency Selection
Product Number
FS781
FS782
FS784
FSOUT Frequency Scaling
1x
2x
4x
Description
1x Modulated Frequency of Input Clock
2x Modulated Frequency of Input Clock
4x Modulated Frequency of Input Clock
Table 2. FSOUT SSCG (Modulated Output Clock) Product Selection
Cypress Semiconductor Corporation
525 Los Coches St.
Milpitas, CA 95035. Tel: 408-263-6300, Fax: 408-263-6571
http://www.cypress.com
Document#: 38-07029 Rev. **
05/07/2001
Page 3 of 13
APPROVED PRODUCT
FS781/82/84
LOW EMI SPECTRUM SPREAD CLOCK
This device contains circuitry to protect the inputs against damage due to high static voltages or electric fields;
however, precautions should be taken to avoid application of any voltage higher than the absolute maximum rated
voltages to this circuit. For proper operation, Vin and Vout should be constrained to the range, VSS < (Vin or
Vout) < VDD. All digital inputs are tied high or low internally. Refers to electrical specifications for operating
supply range.
Absolute Maximum Ratings
Item
Operating Voltage
Input, relative to VSS
Output, relative to VSS
AVDD relative to DVDD
AVSS relative to DVSS
Temperature, Operating
Temperature, Storage
Symbol
VDD
VIRvss
VORvss
∆Vpp
∆Vss
TOP
TST
Min
3.0
-0.3
-0.3
-100
-100
0
- 65
Table 3
Max
6.0
VDD +0.3
VDD +0.3
+100
+100
+ 70
+ 150
Units
VDC
VDC
VDC
mV
mV
0
C
0
C
Electrical Characteristics
Characteristic
Symbol
Min
Typ
Max
Input Low Voltage
VIL
-
-
0.3 * VDD
Input High Voltage
VIH
0.7 * VDD
-
-
Input Low Current
IIL
-
-
100
Input High Current
IIH
-
-
100
Output Low Voltage IOL= 10mA, VDD = 5V
VOL
-
-
0.4
Output High Voltage IOH = 10mA, VDD = 5V
VOH
VDD-1.0
-
-
Output Low Voltage IOL= 6mA, VDD = 3.3V
VOL
-
-
0.4
Output High Voltage IOH = 5mA,VDD = 3.3V
VOH
2.4
-
-
Resistor, Pull Down (Pin-7)
Rpd
60K
125K
200K
Resistor, Pull Up (Pin-3)
Rpu
60K
125K
200K
Input Capacitance (Pin-1)
C
xin
-
8
-
Output Capacitance (Pin-2)
C
xout
-
10
-
5 Volt Dynamic Supply Current (C
L =
No Load)
ICC
-
38
-
3.3 Volt Dynamic Supply Current (C
L =
No Load)
ICC
-
20
-
Short Circuit Current (FSOUT)
ISC
-
25
-
BW% Variations, 3.30V**
BW
-20
0
+20
BW% Variations, 5.00V**
BW
-30
0
+30
Test measurements performed at VDD = 3.3V and 5.0V
±10%,
Xin = 48 MHz, Ta = 0°C to 70°C
**BW% Variations in % from the BW% values give in Loop Filter Value Tables.
Table 4
Units
VDC
VDC
µA
µA
VDC
VDC
VDC
VDC
Ω
Ω
pF
pF
mA
mA
mA
%
%
Cypress Semiconductor Corporation
525 Los Coches St.
Milpitas, CA 95035. Tel: 408-263-6300, Fax: 408-263-6571
http://www.cypress.com
Document#: 38-07029 Rev. **
05/07/2001
Page 4 of 13
APPROVED PRODUCT
FS781/82/84
LOW EMI SPECTRUM SPREAD CLOCK
Timing Characteristics
Characteristic
Output Rise Time Measured at 10% - 90% @ 5 VDC
Output Fall Time Measured at 10% - 90% @ 5 VDC
Output Rise Time Measured at 0.8V - 2.0V @ 5 VDC
Output Fall Time Measured at 0.8V - 2.0 V @ 5 VDC
Output Rise Time Measured at 10% - 90% @ 3.3 VDC
Output Fall Time Measured at 10% - 90% @ 3.3 VDC
Output Rise Time Measured at 0.8V - 2.0V @ 3.3 VDC
Output Fall Time Measured at 0.8V - 2.0 V @ 3.3 VDC
Output Duty Cycle
FSOUT, Cycle to Cycle Jitter, 48 MHz @ 3.30 VDC
(Pin 6)
FSOUT, Cycle to Cycle Jitter, 48 MHz @ 5.0 VDC
(Pin 6)
FSOUT, Cycle to Cycle Jitter, 72 MHz @ 3.30 VDC
(Pin 6)
FSOUT, Cycle to Cycle Jitter, 72 MHz @ 5.0 VDC
(Pin 6)
Table 5
Symbol
tTLH
tTHL
tTLH
tTHL
tTLH
tTHL
tTLH
tTHL
TsymF1
CCJ
CCJ
CCJ
CCJ
Min
2.0
1.7
0.50
0.50
2.6
2.0
0.8
0.78
45
-
-
-
-
Typ
2.2
2.0
0.65
0.65
2.65
2.1
0.95
0.85
50
320
310
270
390
Max
2.5
2.2
0.75
0.75
2.9
2.2
1.1
0.9
55
370
360
325
440
Units
ns
ns
ns
ns
ns
ns
ns
ns
%
pS
pS
pS
pS
Measurements performed at VDD = 3.3 and 5.0V
±
10%, Ta = 0°C to 70°C, CL = 15pF, Xin = 48 MHz.
Range Selection Table
S1
(pin 3)
0
0
1
1
S0
(pin 7)
0
1
0
1
Fin (MHz)
(pin 2/3)
6 - 16
16 - 32
32 - 66
66 - 82
Modulation
FS781
Rate
FSOUT (pin 6)
Fin/120
6 – 16 MHz
Fin/240
16 – 32 MHz
Fin/480
32 – 66 MHz
Fin/720
66– 82 MHz
Table 6
FS782
FSOUT (pin 6)
12 – 32 MHz
32 – 64 MHz
64 – 82 MHz
N/A
FS784
FSOUT (pin 6)
32 – 64 MHz
64 – 82 MHz
N/A
N/A
Cypress Semiconductor Corporation
525 Los Coches St.
Milpitas, CA 95035. Tel: 408-263-6300, Fax: 408-263-6571
http://www.cypress.com
Document#: 38-07029 Rev. **
05/07/2001
Page 5 of 13
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