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VX-722 Dual Frequency HPLL VCXO

LVPECL Applica on Diagrams

LVDS Applica on Diagrams

Figure 6 - Single Resistor Termina on Scheme

Figure 7 - Pull Up Pull Down Termina on

Resistor values are typically 120 to 240 ohms for 3.3V opera on and 82 to 120 ohms for 2.5V

opera on.

Resistor values are typically for 3.3V opera on

For 2.5V opera on, the resistor to ground is 62 ohms and the resistor to supply is 240 ohms

There are numerous applica on notes on termina ng and interfacing PECL logic and the two most common methods are a single resistor to ground, Figure 6,

and a pull-up/pull-down scheme as shown in Figure 7. An AC coupling capacitor is oponal, depending on the applica on and the input logic requirements of

the next stage.

One of the most important considera ons is termina ng the Output and Complementary Outputs equally. An unused output should not be le un-

terminated, and if one of the two outputs is le open it will result in excessive ji er 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 ji er related problems.

Some LVDS structures have an internal 100 ohm resistor on the

input and do not need addional components.

One of the most important considera ons is termina ng the Output and Complementary Outputs equally. An unused output should not be le un-

terminated, and if one of the two outputs is le open it will result in excessive ji er 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 ji er related problems.

Figure 8 - LVDS to LVDS, internal 100Ω

Figure 9 - LVDS to LVDS, External 100Ω and AC block ing caps

240

240

VC

FS

1

2

3

4

5

6

+3.3V

10nF

1nF

10nF

10nF

130

VC

FS

1

2

3

4

5

6

130

+3.3V

82

82

+3.3V

10nF

1nF

10nF

10nF

100

Receiver

VC

FS

1

2

3

4

5

6

+3.3V

10nF

1nF

100

Receiver

VC

FS

1

2

3

4

5

6

+3.3V

10nF

1nF

10nF

10nF

Rev2: 14 November 2012