DATASHEET
SPREAD SPECTRUM CLOCK SYNTHESIZER
Description
The IDT5P50911/2/3/4 is a family of 1.8V/2.5V/3.3V low
power, spread spectrum clock generators capable of
reducing EMI radiation from an input clock. Spread
spectrum technique is capable of reducing the harmonic
frequency amplitude peaks by several dB.
IDT5P50911/2/3/4
Features
•
8-pin DFN package (2x2mm)
8-pin MSOP package (3x4.9mm)
Ordering Information
Output Frequency
5 to 15 MHz - 5P50911NBGI/5P50911DVGI
10 to 30 MHz - 5P50912NBGI/5P50912DVGI
20 to 60 MHz - 5P50913NBGI/5P50913DVGI
40 to 120 MHz - 5P50914NBGI/5P50914DVGI
•
•
•
•
•
Provides a spread spectrum output clock
Crystal input frequency range of 10 to 30 MHz
Output frequency range of 10 to 120 MHz
Center and down spread
Peak reduction by 8 dB to 16 dB typical on 3rd through
19th odd harmonics
•
Low EMI feature can be disabled
•
Operating voltage of 1.8 V, 2.5 or 3.3V
•
RoHS 6 compliant package
Spread Modulation Frequency Table
Part
Number
Output
Multiply
Input
(MHz)
Modulation
(kHz)
Input
(MHz)
Modulation
(kHz)
Modulation
Frequency (kHz)
5P50911
5P50912
5P50913
5P50914
1/2x
1x
2x
4x
10
27
30
81
Input frequency
*27/10000
Block Diagram
VDD
OE
S1:S0
X1
Crystal
Oscillator
X2
Optional tuning
crystal capacitors
PLL Clock
Synthesizer with
Spread Spectrum
Circuitry
CLKOUT
GND
IDT®
SPREAD SPECTRUM CLOCK SYNTHESIZER
1
IDT5P50911/2/3/4
REV D 070214
IDT5P50911/2/3/4
SPREAD SPECTRUM CLOCK SYNTHESIZER
CLOCK SYNTHESIZER
Pin Assignment
X1/ICLK
VDD
OE
S0
4
5
1
8
X2
GND
CLKOUT
S1
8-pin DFN
8 -pin MSOP
Spread Direction and Percentage Select Table
S1
S0
Spread
Direction
Spread
Percentage
0
0
1
1
0
1
0
1
OFF
Center
Center
Down
--
±0.5
±1.5
-0.5
Pin Description
Pin
Number
Pin
Name
X1
Pin Type
XI
Pin Description
1
2
3
4
5
6
7
8
Crystal input. Connect this pin to a crystal.
Voltage supply. Connect to 1.8 V ±0.1 V, 2.5 V ±10% or 3.3 V ±10%,
Output enable. Tri-states CLK output when low. Internal pull-up.
Function select 0 input. Selects spread amount and direction per table above.
Internal pull-down resistor.
Function select 1 input. Selects spread amount and direction per table above.
Internal pull-down resistor.
Clock output. Weal pull-down when OE low.
Connect to ground.
Crystal output. Connect this pin to a crystal.
VDD
OE
S0
S1
CLKOUT
GND
X2
Power
Input
Input
Input
Output
Power
XO
IDT®
SPREAD SPECTRUM CLOCK SYNTHESIZER
2
IDT5P50911/2/3/4
REV D 070214
IDT5P50911/2/3/4
SPREAD SPECTRUM CLOCK SYNTHESIZER
CLOCK SYNTHESIZER
External Components
Decoupling Capacitor
As with any high-performance mixed-signal IC, the
IDT5P50911/2/3/4 must be isolated from system power
supply noise to perform optimally.
A decoupling capacitor of 0.01µF must be connected
between each VDD and the PCB ground plane.
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
IDT5P50911/2/3/4. This includes signal traces just
underneath the device, or on layers adjacent to the ground
plane layer used by the device.
Spread Spectrum Profile
The IDT5P50911/2/3/4 is a low EMI clock generator using
an optimized frequency slew rate algorithm to facilitate down
stream tracking of zero delay buffers and other PLL devices.
The modulation rate is directly relate to the input crystal
frequency.
For input frequency ICLK, then use the modulation
frequency indicated for the part below.
Series Termination Resistor
Clock output traces over one inch should use series
termination. To series terminate a 50 trace (a commonly
used trace impedance), place a 33 resistor in series with
the clock line, as close to the clock output pin as possible.
The nominal impedance of the clock output is 20.
Crystal Load Capacitors
The device crystal connections should include pads for
small capacitors from X1 to ground and from X2 to ground.
These capacitors are used to adjust the stray capacitance of
the board to match the nominally required crystal load
capacitance. Because load capacitance can only be
increased in this trimming process, it is important to keep
stray capacitance to a minimum by using very short PCB
traces (and no vias) between the crystal and device. Crystal
capacitors, if needed, must be connected from each of the
pins X1 and X2 to ground.
The value (in pF) of these crystal caps should equal (C
L
-12
pF)*2. In this equation, C
L
= crystal load capacitance in pF.
Example: For a crystal with a 16 pF load capacitance, each
crystal capacitor would be 8 pF [(16-12) x 2 = 8].
Modulation R
ate
Frequency
Time
Modulation Frequency = Input Frequency/10000
Ex. Input Frequency = 20 MHz
Modulation Frequency = 20 MHz/10000 = 2 kHz
PCB Layout Recommendations
For optimum device performance and lowest output phase
noise, the following guidelines should be observed.
1) The 0.01µF decoupling capacitors 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
capacitors and VDD pins. The PCB trace to VDD pins
should be kept as short as possible, as should the PCB
trace to the ground via.
2) To minimize EMI, the 33 series termination resistor (if
needed) should be placed close to the clock output.
IDT®
SPREAD SPECTRUM CLOCK SYNTHESIZER
3
IDT5P50911/2/3/4
REV D 070214
IDT5P50911/2/3/4
SPREAD SPECTRUM CLOCK SYNTHESIZER
CLOCK SYNTHESIZER
Absolute Maximum Ratings
Stresses above the ratings listed below can cause permanent damage to the IDT5P50911/2/3/4. 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
Ambient Operating Temperature
Storage Temperature
Junction Temperature
Soldering Temperature
-0.5 V to 7.0 V
Rating
-0.5 V to VDD +0.5 V
-40 to +85C
-50 to +150C
125C
260C
Recommended Operation Conditions
Parameter
Ambient Operating Temperature
Power Supply Voltage VDD (measured in respect to GND)
Min.
-40
+1.7
+2.25
+2.97
Typ.
+1.8
+2.5
+3.3
Max.
+85
+1.9
+2.75
+3.63
Units
C
V
V
V
IDT®
SPREAD SPECTRUM CLOCK SYNTHESIZER
4
IDT5P50911/2/3/4
REV D 070214
京公网安备 11010802033920号
EEWORLD
