VSC7969 データシートの表示（PDF） - Vitesse Semiconductor

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VSC7969

3.125Gb/s Integrated Transimpedance and Limiting Amplifier with Signal Detect

Vitesse Semiconductor 

VITESSE

SEMICONDUCTOR CORPORATION

3.125Gb/s Integrated Transimpedance

and Limiting Amplifier with Signal Detect

Advance Product Information

VSC7969

Circuit Description

The VSC7969 data path consists of several stages: transimpedance input stage, limiting amplifier, and out-

put driver. The transimpedance amplifier accepts current from a photodetector connected to the input pad ‘IN’

and converts the input current to a differential output voltage. The signal then travels to the second stage limit-

ing amplifier which provides DC restoration, eliminating the DC component of the input signal. The linear pho-

tocurrent monitor and signal detect function is also provided by this stage. The final stage consists of an output

driver with a differential pair connected to VCC via 50Ω internal pull-up resistors. The overall effective differ-

ential transimpedance of the VSC7969 is typically 27kΩ. The limited output single-ended voltage swing is typ-

ically 250mVp-p.

Design Guidelines

Power Supply

The VSC7969 is supplied by a single supply voltage; for +3.3V operation, the supply votlage should be

applied to only VCCS. For +5V operation, the supply voltage should be applied to only VCCD.

Data Outputs

The outputs of the VSC7969 need to be AC-coupled. This capacitor will determine the low frequency cut-

off for the system, which is directly related to the receiver’s deterministic jitter. For ATM/SONET or other

applications using PRBS NRZ data, select a capacitor of at least 0.1µF or greater, which provides less than

32kHz low frequency cutoff. For Fibre Channel, Gigabit Ethernet, or other applications requiring 8B/10B data

coding, select a capacitor of at least 0.01µF or greater, which provides less than 320kHz low frequency cutoff.

The outputs can be used single-ended or differential. For best performance, differential operation is recom-

mended. If single-ended operation is necessary, the unused output should be AC-coupled and terminated with

an impedance equal to the load on the pin in use.

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

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

Internet: www.vitesse.com

G52355-0, Rev 2.0

02/09/01

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