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Environmental and IR Compliance

Table 5. Environmental Compliance

Parameter

Condition

Mechanical Shock

MIL-STD-883 Method 2002

Mechanical Vibration

MIL-STD-883 Method 2007

Temperature Cycle

MIL-STD-883 Method 1010

Solderability

MIL-STD-883 Method 2003

Fine and Gross Leak

Fine and Gross Leak

MIL-STD-883 Method 1014

Resistance to Solvents

MIL-STD-202 Method 215

Moisture Sensitivity Level

Moisture Sensitivity Level

MSL1

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LVPECL Application Diagrams

The VM-822 incorporates a standard LVPECL output scheme, which are un-terminated emitters as shown in Figure 8. There are numerous application

notes on terminating and interfacing LVPECL logic and the two most common methods are a single resistor to ground, Figure 9, and a pull-up/pull-down

scheme as shown in Figure 10. An AC coupling capacitor is optional, depending on the application and the input logic requirements of the next stage.

Figure 11. Single Resistor Termination Scheme

Figure 12. Pull-Up Pull Down Termination

Resistor values are typically 140 ohms for 3.3V operation

and 82.5ohms 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 250 ohms

100

LVDS

Driver

LVDS

Receiver

100

LVDS

Driver

Receiver

Figure 13. LVDS to LVDS Connection, Internal 100ohm

Figure 14. LVDS to LVDS Connection

External 100ohm and AC blocking caps

Some LVDS structures have an internal 100 ohm resistor on the

input and do not need additional components.

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.

LVDS Application Diagrams

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 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.

140Ω

140Ω