VITESSE

SEMICONDUCTOR CORPORATION

Preliminary Data Sheet

VSC7940

SONET/SDH 3.125Gb/s

Laser Diode Driver with Automatic Power Control

G52357-0, Rev 3.2

Page 13

05/11/01

© VITESSE SEMICONDUCTOR CORPORATION • 741 Calle Plano • Camarillo, CA 93012

Tel: (800) VITESSE • FAX: (805) 987-5896 • Email: prodinfo@vitesse.com

Internet: www.vitesse.com

Select Resistors for MODMON and BIASMON

Assuming the modulation and bias currents never exceed 120mA, the following equations provide values

MODMON would indicate a modulation current of:

Wire Bonding

For best performance, gold ball-bonding techniques are recommended. Wedge bonding is not recom-

mended. For best performance and to minimize inductance keep wire bond lengths short.

PCB Layout Guidelines

Use high frequency PCB layout techniques with solid ground planes to minimize crosstalk and EMI. Keep

high speed traces as short as possible for signal integrity. The output traces to the laser diode must be short to

minimize inductance. Short output traces will provide best performance.