DATASHEET
SPREAD SPECTRUM CLOCK GENERATOR
Description
The ICS7152A-02 and -11 are clock generators for EMI
(Electromagnetic Interference) reduction (see below for
frequency ranges and multiplier ratios). 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.
ICS7152A
Features
•
•
•
•
•
•
•
•
•
•
VDD
Operating voltage of 3.3 V ±0.3 V
Packaged in 8-pin SOIC
Input frequency range of 16.6 to 134.0 MHz
Output frequency range of 16.6 to 134.0 MHz
Provides a spread spectrum clock output (±0.5%, ±1.5%
center spread; -1.0%, -3.0% down spread)
Low cycle-to-cycle jitter - less than 100 ps
Advanced, low-power CMOS process
Industrial and commercial temperature ranges
Pb (lead) free package, RoHS compliant
Pin compatible with Fujitsu MB88152-102 and -111
Block Diagram
SEL
FREQ
XENS
XIN
PLL Clock
Synthesis
and Spread
Spectrum
Circuitry
Clock Buffer/
Crystal
Ocsillator
CKOUT
XOUT
External caps required with crystal for
accurate tuning of the clock
GND
Product Lineup
Product
Input Frequency Range
Modulation Type
Modulation Enable Pin
ICS7152AM-02, ICS7152AMI-02
ICS7152AM-11, ICS7152AMI-11
40.0 MHz to 134.0 MHz
16.6 MHz to 67.0 MHz
Down spread
Center spread
Yes
IDT™ / ICS™
SPREAD SPECTRUM CLOCK GENERATOR
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ICS7152A
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ICS7152A
SPREAD SPECTRUM CLOCK GENERATOR
SSCG
Pin Assignment
XIN
XOUT
GND
SEL
1
2
3
4
8
7
6
5
8 pin (150 mil) SOIC
XENS
FREQ
VDD
CKOUT
Spread Direction and Percentage
Select Table
SEL
Pin 4
Spread
Direction
Spread
Percentage (%)
Part Number
0
Center
Down
±0.5
-1.0
±1.5
-3.0
ICS7152AM-11
ICS7152AM-02
ICS7152AM-11
ICS7152AM-02
1
Center
Down
Modulation Enable Select Table
XENS
Pin 8
0
1
Modulation
Modulation
No modulation
Frequency Select Table
FREQ
Pin 7
Frequency
0
16.6 to 40 MHz
40 to 80 MHz
ICS7152AM-11
ICS7152AM-02
ICS7152AM-11
ICS7152AM-02
1
33 to 67 MHz
66 to 134 MHz
Pin Descriptions
Pin
Number
Pin
Name
Pin Type
Pin Description
1
2
3
4
5
6
7
8
XIN
XOUT
GND
SEL
CKOUT
VDD
FREQ
XENS
Input
Output
Power
Input
Output
Power
Input
Input
Crystal/clock input pin.
Crystal.
Connect to ground.
Spread modulation select.
Clock output.
Connect to +3.3 V.
Frequency select.
Modulation enable select.
IDT™ / ICS™
SPREAD SPECTRUM CLOCK GENERATOR
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SPREAD SPECTRUM CLOCK GENERATOR
SSCG
External Components
The ICS7152A requires a minimum number of external
components for proper operation.
Crystal caps (pF) = (C
L
- 6) x 2
In the equation, C
L
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 3 and 6, 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 ICS7152A 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
.
Modulation Rate
PCB Layout Recommendations
For optimum device performance and lowest output phase
noise, the following guidelines should be observed.
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
ICS7152A. This includes signal traces just underneath the
device, or on layers adjacent to the ground plane layer used
by the device.
Frequency
Time
Crystal Information
The crystal used should be a fundamental mode, 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
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SPREAD SPECTRUM CLOCK GENERATOR
SSCG
Absolute Maximum Ratings
Stresses above the ratings listed below can cause permanent damage to the ICS7152A. 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
Supply Voltage, VDD
All Inputs and Outputs (referenced to GND)
Ambient Operating Temperature
Storage Temperature
Junction Temperature
Soldering Temperature
Overshoot (V
IOVER
)
Undershoot (V
IUNDER
)
-0.5 to 4.0 V
Rating
-0.5 V to VDD+0.5 V
-40 to +85° C
-55 to +125° C
-40 to +125° C
260° C
VDD + 1.0 V (t
OVER
< 50 ns) max
GND - 1.0 V (t
UNDER
< 50 ns) min
Overshoot/Undershoot
t
UNDER
< 50 ns
V
IOVER
< V
DD
+ 1.0 V
V
DD
GND
V
IUNDER
< GND - 1.0 V
Input pin
t
OVER
< 50 ns
Recommended Operation Conditions
Parameter
Ambient Operating Temperature
Power Supply Voltage (measured in respect to GND)
Min.
-40
+3.0
Typ.
3.3
Max.
+85
3.6
Units
°
C
V
IDT™ / ICS™
SPREAD SPECTRUM CLOCK GENERATOR
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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
Operating Voltage
Supply Current
Symbol
VDD
IDD
Conditions
No load, at 3.3 V,
output = 24 MHz
SEL, FREQ, XENS
XIN, Input slew rate
3 V/ns, 16.6 to 100
MHz
XIN, Input slew rate
3 V/ns, 100 to 134
MHz
SEL, FREQ, XENS
XIN, Input slew rate
3 V/ns, 16.6 to 100
MHz
XIN, Input slew rate
3 V/ns, 100 to 134
MHz
Min.
3.0
Typ.
3.3
10
Max.
3.6
14
VDD + 0.3
VDD + 0.3
Units
V
mA
V
V
VDD x 0.8
VDD x 0.8
Input High Voltage
V
IH
VDD x 0.9
VDD + 0.3
V
GND
GND
VDD x 0.20
VDD x 0.20
V
V
Input Low Voltage
V
IL
GND
VDD x 0.10
V
Output High Voltage
Output Low Voltage
Input Capacitance
V
OH
V
OL
C
IN
CKOUT, I
OH
= -4 mA
CKOUT, I
OL
= 4 mA
XIN, SEL, XENS
CKOUT, 16.6 to 67
MHz
VDD - 0.5
GND
VDD
0.4
16
15
10
7
25
V
V
pF
pF
pF
pF
Ω
Load Capacitance
C
L
CKOUT, 67 to 100
MHz
CKOUT, 100 to 134
MHz
Output Impedance
Z
O
CKOUT, 16.6 to 134
MHz
IDT™ / ICS™
SPREAD SPECTRUM CLOCK GENERATOR
5
ICS7152A
REV E 051310
