DATASHEET
ICS7151A-50
SPREAD SPECTRUM CLOCK GENERATOR
Description
Features
The ICS7151A-50 is a clock generator for EMI
(Electromagnetic Interference) reduction. Spectral peaks
are attenuated by modulating the system clock frequency.
Down or center spread profiles are selectable. Down
spread will not exceed the maximum frequency of an
unspread clock, and center spread does not change the
average operating frequency of the system
•
•
•
•
•
•
IDT offers many other clocks for computers and computer
peripherals. Consult IDT when you need to remove crystals
and oscillators from your board.
Operating voltage of 3.3 V ±0.3 V
Packaged in 8-pin SOIC
Available in Pb (lead) free package
Input frequency range of 16.5 to 33.4 MHz
Output frequency ranges of 8.3 to 16.7 MHz
Provides a spread spectrum clock output (±0.5%, ±1.5%
center spread; -1.0%, -3.0% down spread)
• Multiplication rate of x1/2
• Advanced, low-power CMOS process
• Pin compatible with the Fujitsu MB88151-500
NOTE: EOL for non-green parts to occur on 5/13/10
per PDN U-09-01
Block Diagram
VDD
S1:0
2
PLL Clock
Synthesis
and Spread
Spectrum
Circuitry
ENS
XIN
CKOUT
Clock Buffer/
Crystal
Ocsillator
XOUT
External caps required with crystal for
accurate tuning of the clock
IDT™ / ICS™ SPREAD SPECTRUM CLOCK GENERATOR
GND
1
ICS7151A-50
REV B 110409
ICS7151A-50
SPREAD SPECTRUM CLOCK GENERATOR
SSCG
Pin Assignment
Spread Direction and Percentage
Select Table
XIN
1
8
XOUT
GND
2
7
S0
3
S1
4
VDD
S1
Pin 4
S0
Pin 3
Spread
Direction
Spread
Percentage (%)
6
ENS
0
0
Center
±1.5
5
CKOUT
0
1
Center
±0.5
1
0
Down
-1.0
1
1
Down
-3.0
8 pin (150 mil) SOIC
ENS
(note 1)
Modulation
0
No Modulation
1
Modulation
Notes:
1. Pin 1 has a pull-up resistor.
Pin Descriptions
Pin
Number
Pin
Name
Pin Type
Pin Description
1
XIN
Input
Crystal pin/clock input pin.
2
GND
Power
Connect to ground.
3
S0
Input
Select pin 0. Spread modulation select.
4
S1
Input
Select pin 1. Spread modulation select.
5
CKOUT
Output
6
ENS
Input
Modulation enable. Internal pull-up resistor.
7
VDD
Power
Connect to +3.3 V.
8
XOUT
Output
Crystal connection pin.
Clock output.
IDT™ / ICS™ SPREAD SPECTRUM CLOCK GENERATOR
2
ICS7151A-50
REV B 110409
ICS7151A-50
SPREAD SPECTRUM CLOCK GENERATOR
SSCG
External Components
Crystal caps (pF) = (CL - 6) x 2
The ICS7151A-50 requires a minimum number of external
components for proper operation.
In the equation, CL is the crystal load capacitance. So, for a
crystal with a 16 pF load capacitance, two 20 pF [(16-6) x 2]
capacitors should be used.
Decoupling Capacitor
A decoupling capacitor of 0.01µF must be connected
between GND and VDD on pins 2 and 7, as close to these
pins as possible. For optimum device performance, the
decoupling capacitor should be mounted on the component
side of the PCB. Avoid the use of vias in the decoupling
circuit.
Spread Spectrum Profile
The ICS7151A-50 low EMI clock generator uses a triangular
frequency modulation profile for optimal down stream
tracking of zero delay buffers and other PLL devices. The
frequency modulation amplitude is constant with variations
of the input frequency.
Series Termination Resistor
Series termination should be used on the clock output. To
series terminate a 50Ω trace (a commonly used trace
impedance) place a 27Ω resistor in series with the clock line,
as close to the clock output pin as possible. The nominal
impedance of the clock output is 25Ω.
Frequency
Modulation Rate
PCB Layout Recommendations
For optimum device performance and lowest output phase
noise, the following guidelines should be observed.
Time
1) The 0.01µF decoupling capacitor should be mounted on
the component side of the board as close to the VDD pin as
possible. No vias should be used between the decoupling
capacitor and VDD pin. The PCB trace to VDD pin should
be kept as short as possible, as should the PCB trace to the
ground via.
2) To minimize EMI, the 27Ω series termination resistor (if
needed) should be placed close to the clock output.
3) An optimum layout is one with all components on the
same side of the board, minimizing vias through other signal
layers. Other signal traces should be routed away from the
ICS7151A-50. This includes signal traces just underneath
the device, or on layers adjacent to the ground plane layer
used by the device.
Crystal Information
The crystal used should be a fundamental mode (do not use
third overtone), parallel resonant. Crystal capacitors should
be connected from pins X1 to ground and X2 to ground to
optimize the initial accuracy. The value of these capacitors
is given by the following equation:
IDT™ / ICS™ SPREAD SPECTRUM CLOCK GENERATOR
3
ICS7151A-50
REV B 110409
ICS7151A-50
SPREAD SPECTRUM CLOCK GENERATOR
SSCG
Absolute Maximum Ratings
Stresses above the ratings listed below can cause permanent damage to the ICS7151A-50. These ratings, which
are standard values for IDT commercially rated parts, are stress ratings only. Functional operation of the device at
these or any other conditions above those indicated in the operational sections of the specifications is not implied.
Exposure to absolute maximum rating conditions for extended periods can affect product reliability. Electrical
parameters are guaranteed only over the recommended operating temperature range.
Item
Rating
Supply Voltage, VDD
-0.5 to 4.0 V
All Inputs and Outputs (referenced to GND)
-0.5 V to VDD+0.5 V
Ambient Operating Temperature
-40 to +85° C
Storage Temperature
-55 to +125° C
Junction Temperature
-40 to +125° C
Soldering Temperature
260° C
Overshoot (VIOVER)
VDD + 1.0 V (tOVER < 50 ns)
Undershoot (VIUNDER)
GND - 1.0 V (tUNDER < 50 ns)
Overshoot/Undershoot
tUNDER < 50 ns
VIOVER < VDD + 1.0 V
VDD
Input pin
tOVER < 50 ns
GND
VIUNDER < GND - 1.0 V
Recommended Operation Conditions
Parameter
Min.
Ambient Operating Temperature
-40
Power Supply Voltage (measured in respect to GND)
+3.0
IDT™ / ICS™ SPREAD SPECTRUM CLOCK GENERATOR
4
Typ.
3.3
Max.
Units
+85
°C
3.6
V
ICS7151A-50
REV B 110409
ICS7151A-50
SPREAD SPECTRUM CLOCK GENERATOR
SSCG
DC Electrical Characteristics
Unless stated otherwise, VDD = 3.3 V ±0.3 V, Ambient Temperature -40 to +85° C
Parameter
Symbol
Operating Voltage
VDD
Supply Current
IDD
Conditions
Min.
Typ.
Max.
Units
3.0
3.3
3.6
V
10
14
mA
16.5
33.4
MHz
No load, at 3.3 V,
output = 24 MHz
Input Frequency
Input High Voltage
VIH
XIN, S0, S1, ENS
VDD * 0.8
VDD + 0.3
V
Input Low Voltage
VIL
XIN, S0, S1, ENS
0.0
VDD * 0.20
V
Output High Voltage
VOH
CKOUT, IOH = -4 mA
2.0
Output Low Voltage
VOL
CKOUT, IOL = 4 mA
0.4
V
Input Capacitance
CIN
XIN, S0, S1, ENS
16
pF
CKOUT, 8.3 to 66.7
MHz
15
pF
CKOUT, 66.7 to 100
MHz
10
pF
CKOUT, 100 to 133.4
MHz
7
pF
400
kΩ
Load Capacitance
Input Pull-up Resistor
CL
ENS
RPU
V
100
240
AC Electrical Characteristics
Unless stated otherwise, VDD = 3.3 V ±0.3 V, Ambient Temperature -40 to +85° C
Parameter
Symbol
Conditions
Min.
Typ.
Max.
Units
Oscillation Frequency
fX
Fundamental
oscillation
16.5
33.4
MHz
Input Frequency
fIN
XIN
16.5
33.4
MHz
CKOUT, 2-frequency
division
8.3
16.7
MHz
XIN, 16.5 to 33.4 MHz
40
60
%
CKOUT, 1.5 V
40
60
%
CKOUT, 0.4 to 2.4 V,
load capacitance 15 pF
0.5
TBD
3.0
V/ns
TBD
200
ps
5
ms
Output Frequency
fOUT
Input Clock Duty Cycle
Output Clock Duty Cycle
tDCC
Output Slew Rate
50
Cycle to Cycle Jitter
tJC
No load, standard
deviation
Lock Time
tLK
CKOUT
2
CKOUT=TBD
33
Modulation Frequency
fMOD
IDT™ / ICS™ SPREAD SPECTRUM CLOCK GENERATOR
5
kHz
ICS7151A-50
REV B 110409
ICS7151A-50
SPREAD SPECTRUM CLOCK GENERATOR
SSCG
Input Frequency (fIN = 1/tIN)
tIN
0.8 VDD
CKIN
Output Slew Rate
2.4 V
0.4 V
CKOUT
tr
tf
SR = (2.4 - 0.4) /tr, SR = (2.4 - 0.4) /tf
Thermal Characteristics
Parameter
Thermal Resistance Junction to
Ambient
Thermal Resistance Junction to Case
IDT™ / ICS™ SPREAD SPECTRUM CLOCK GENERATOR
Symbol
Conditions
Min.
Typ.
Max. Units
θJA
Still air
150
° C/W
θJA
1 m/s air flow
140
° C/W
θJA
3 m/s air flow
120
° C/W
40
° C/W
θJC
6
ICS7151A-50
REV B 110409
ICS7151A-50
SPREAD SPECTRUM CLOCK GENERATOR
SSCG
Package Outline and Package Dimensions (8-pin SOIC, 150 Mil. Body)
Package dimensions are kept current with JEDEC Publication No. 95
Millimeters
8
Symbol
E
Min
A
A1
B
C
D
E
e
H
h
L
α
H
INDEX
AREA
1 2
D
Inches*
Max
Min
1.35
1.75
0.10
0.25
0.33
0.51
0.19
0.25
4.80
5.00
3.80
4.00
1.27 BASIC
5.80
6.20
0.25
0.50
0.40
1.27
0°
8°
Max
.0532
.0688
.0040
.0098
.013
.020
.0075
.0098
.1890
.1968
.1497
.1574
0.050 BASIC
.2284
.2440
.010
.020
.016
.050
0°
8°
*For reference only. Controlling dimensions in mm.
A
h x 45
A1
C
-Ce
SEATING
PLANE
B
L
.10 (.004)
C
*Ordering Information
Part / Order Number
Marking
Shipping Packaging
Package
Temperature
7151AM-50*
7151AM-50T*
7151AM-50LF
7151AM-50LFT
7151AMI-50*
7151AMI-50T*
7151AMI-50LF
7151AMI-50LFT
7151AM50
7151AM50
151AM50L
151AM50L
151AMI50
151AMI50
51AMI50L
51AMI50L
Tubes
Tape and Reel
Tubes
Tape and Reel
Tubes
Tape and Reel
Tubes
Tape and Reel
8-pin SOIC
8-pin SOIC
8-pin SOIC
8-pin SOIC
8-pin SOIC
8-pin SOIC
8-pin SOIC
8-pin SOIC
0 to +70° C
0 to +70° C
0 to +70° C
0 to +70° C
-40 to +85° C
-40 to +85° C
-40 to +85° C
-40 to +85° C
NOTE: EOL for non-green parts to occur on 5/13/10 per PDN U-09-01
Parts that are ordered with a "LF" suffix to the part number are the Pb-Free configuration and are RoHS compliant.
While the information presented herein has been checked for both accuracy and reliability, Integrated Device Technology (IDT) assumes
no responsibility for either its use or for the infringement of any patents or other rights of third parties, which would result from its use. No
other circuits, patents, or licenses are implied. This product is intended for use in normal commercial applications. Any other applications
such as those requiring extended temperature range, high reliability, or other extraordinary environmental requirements are not
recommended without additional processing by IDT. IDT reserves the right to change any circuitry or specifications without notice. IDT
does not authorize or warrant any IDT product for use in life support devices or critical medical instruments.
IDT™ / ICS™ SPREAD SPECTRUM CLOCK GENERATOR
7
ICS7151A-50
REV B 110409
ICS7151A-50
SPREAD SPECTRUM CLOCK GENERATOR
SSCG
Revision History
Rev.
Originator
Date
A
J. Sarma
10/20/05
Rev A; new device/datasheet.
11/04/09
Added EOL note for non-green parts.
B
Description of Change
IDT™ / ICS™ SPREAD SPECTRUM CLOCK GENERATOR
8
ICS7151A-50
REV B 110409
ICS7151A-50
SPREAD SPECTRUM CLOCK GENERATOR
SSCG
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