Rainbow-electronics MAX3622 Manuel d'utilisateur télécharger pdf (Page 7)

Interfacing with LVPECL Outputs

The equivalent LVPECL output circuit is given in Figure

7. This output is designed to drive a pair of 50Ω trans-

mission lines terminated with 50Ω to V

= V

- 2V. If

a separate termination voltage (V

) is not available,

other termination methods can be used such as shown

in Figures 5 and 6. Unused outputs should be disabled

and may be left open. For more information on LVPECL

terminations and how to interface with other logic fami-

lies, refer to Maxim Application Note

HFAN-01.0:

Introduction to LVDS, PECL, and CML

Interface Models

Figure 7 and Figure 8 show examples of interface models.

MAX3622

X_IN

X_OUT

27pF

25MHz

CRYSTAL

= 18pF)

33pF

Figure 4. Crystal, Capacitors Connection

Low-Jitter, Precision Clock Generator

with Two Outputs

_______________________________________________________________________________________ 7

MAX3622

82Ω

= 50Ω

82Ω

130Ω 130Ω

+3.3V

HIGH

IMPEDANCE

Figure 5. Thevenin Equivalent of Standard PECL Termination

MAX3622

150Ω

100Ω

= 50Ω

HIGH

IMPEDANCE

150Ω

0.1μF

NOTE: AC-COUPLING IS OPTIONAL.

0.1μF

Figure 6. AC-Coupled PECL Termination

ESD

STRUCTURES

Figure 7. Simplified LVPECL Output Circuit Schematic

10Ω

ESD

STRUCTURES

QA_C

GNDO_A

DISABLE

DDO_A

Figure 8. Simplified LVCMOS Output Circuit Schematic

1 2 3 4 5 6 7 8 9

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Rainbow-electronics MAX3622 Manuel d'utilisateur Page 7

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