LVPECL Application Diagrams
Figure 7. Standard PECL Output Configuration Figure 8. Single Resistor Termination Scheme
Figure 9. Pull-Up Pull Down Termination
Resistor values are typically 120 to 240 ohms
for 3.3V operation.
Resistor values are typically 82 to 120 ohms
for 2.5V operation.
Resistor values are typically for 3.3V operation
For 2.5V operation, the resistor to ground is 62
ohms and the resistor to supply is 240 ohms
The VCC6 incorporates a standard PECL output scheme, which are un-terminated emitters as shown in Figure 7. There are numerous application notes on
terminating and interfacing PECL logic and the two most common methods are a single resistor to ground, Figure 8, and a pull-up/pull-down scheme as
shown in Figure 9. An AC coupling capacitor is optional, depending on the application and the input logic requirements of the next stage.
LVDS Application Diagrams
VCC
LVDS
Driver
LVDS
Receiver
LVDS
Driver
Receiver
100ȍ
100ȍ
OUT+
OUT-
Figure 11. LVDS to LVDS Connection, Internal 100ohm
Some LVDS structures have an internal 100 ohm resistor on the
input and do not need additional components.
Figure 12. LVDS to LVDS Connection
External 100ohm and AC blocking caps
Some input structures may not have an internal 100 ohm
resistor on the input and will need an external 100ohm
resistor for impedance matching. Also, the input may have
an internal DC bias which may not be compatible with
LVDS levels, AC blocking capacitors can be used.
Figure 10 Standard LVDS
Output Configuration
One of the most important considerations is terminating the Output and Complementary Outputs equally. An unused output should not be left un-termi-
nated, and if it one of the two outputs is left open it will result in excessive jitter on both. PC board layout must take this and 50 ohm impedance matching
into account. Load matching and power supply noise are the main contributors to jitter related problems.
Environmental and IR Compliance
Table 4. Environmental Compliance
Parameter
Mechanical Shock
Mechanical Vibration
Temperature Cycle
Solderability
Condition
MIL-STD-883 Method 2002
MIL-STD-883 Method 2007
MIL-STD-883 Method 1010
MIL-STD-883 Method 2003
MIL-STD-883 Method 1014
MIL-STD-883 Method 2015
MSL1
Fine and Groossss LLeeaakk
Resistance to Solvents
Moisture Sensitivity Level
Contact Pads
Gold over Nickel
Vectron International • 267 Lowell Road, Hudson, NH 03051 • Tel: 1-88-VECTRON-1 • http://www.vectron.com
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