IDT8N3SV76 Data Sheet LVPECL-FREQUENCY PROGRAMMABLE VCXO
IDT8N3SV76CCD
REVISION A NOVEMBER 19, 2013 10 ©2013 Integrated Device Technology, Inc.
Parameter Measurement Information, continued
Output Rise/Fall Time
Applications Information
Termination for 3.3V LVPECL Outputs
The clock layout topology shown below is a typical termination for
LVPECL outputs. The two different layouts mentioned are
recommended only as guidelines.
The differential outputs are low impedance follower outputs that
generate ECL/LVPECL compatible outputs. Therefore, terminating
resistors (DC current path to ground) or current sources must be
used for functionality. These outputs are designed to drive 50
transmission lines. Matched impedance techniques should be used
to maximize operating frequency and minimize signal distortion.
Figures 1A and 1B show two different layouts which are
recommended only as guidelines. Other suitable clock layouts may
exist and it would be recommended that the board designers
simulate to guarantee compatibility across all printed circuit and clock
component process variations.
Figure 1A. 3.3V LVPECL Output Termination Figure 1B. 3.3V LVPECL Output Termination
nQ
Q
R1
84
R2
84
3.3V
R3
125
R4
125
Z
o
=50
Z
o
=50
LVPECL Input
3.3V
3.3V
+
_
IDT8N3SV76 Data Sheet LVPECL-FREQUENCY PROGRAMMABLE VCXO
IDT8N3SV76CCD
REVISION A NOVEMBER 19, 2013 11 ©2013 Integrated Device Technology, Inc.
Termination for 2.5V LVPECL Outputs
Figure 2A and Figure 2B show examples of termination for 2.5V
LVPECL driver. These terminations are equivalent to terminating 50
to V
CC
–2V.ForV
CC
= 2.5V, the V
CC
2V is very close to ground
level. The R3 in Figure 2B can be eliminated and the termination is
shown in Figure 2C.
Figure 2A. 2.5V LVPECL Driver Termination Example
Figure 2C. 2.5V LVPECL Driver Termination Example
Figure 2B. 2.5V LVPECL Driver Termination Example
2.5V LVPECL Driver
V
CC
= 2.5V
2.5V
2.5V
50Ω
50Ω
R1
250
Ω
R3
250Ω
R2
62.5
Ω
R4
62.5
Ω
+
2.5V LVPECL Driver
V
CC
= 2.5V
2.5V
50Ω
50Ω
R1
50
Ω
R2
50
Ω
+
2.5V LVPECL Driver
V
CC
= 2.5V
2.5V
50Ω
50Ω
R1
50
Ω
R2
50Ω
R3
18Ω
+
IDT8N3SV76 Data Sheet LVPECL-FREQUENCY PROGRAMMABLE VCXO
IDT8N3SV76CCD
REVISION A NOVEMBER 19, 2013 12 ©2013 Integrated Device Technology, Inc.
Schematic Layout
Figure 3 shows an example of IDT8N3SV76 application schematic.
In this example, the device is operated at V
CC
= 3.3V. As with any
high speed analog circuitry, the power supply pins are vulnerable to
random noise. To achieve optimum jitter performance, power supply
isolation is required.
In order to achieve the best possible filtering, it is recommended that
the
placement of the filter components be on the device side of the
PCB as close to the power pins as possible. If space is limited, the
0.1µF capacitor in each power pin filter should be placed on the
device side of the PCB and the other components can be placed on
the opposite side.
Power supply filter recommendations are a general guideline to be
used
for reducing external noise from coupling into the devices. The
filter performance is designed for a wide range of noise frequencies.
This low-pass filter starts to attenuate noise at approximately 10 kHz.
If a specific frequency noise component is known, such as switching
power supplies frequencies, it is recommended that component
values be adjusted and if required, additional filtering be added.
Additionally, good general design practices for power plane voltage
stability suggests adding bulk capacitance in the local area of all
devices.
The schematic example focuses on functional connections and is not
configur
ation specific. Refer to the pin description and functional
tables in the datasheet to ensure that the logic control inputs are
properly set.
Figure 3. IDT8N3SV76 Application Schematic

8N3SV76LC-0099CDI8

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Description:
IC OSC VCXO 187.5MHZ 6-CLCC
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