3.3 V, 3.2 Gbps,

Limiting Amplifier

ADN2891

Rev. A

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©2005 Analog Devices, Inc. All rights reserved.

FEATURES

GENERAL DESCRIPTION

Input sensitivity: 4 mV p-p

The ADN2891 is a 3.2 Gbps limiting amplifier with integrated

loss-of-signal (LOS) detection circuitry and a received signal

strength indicator (RSSI). This part is optimized for SONET,

Gigabit Ethernet (GbE), and Fibre Channel optoelectronic

conversion applications. The ADN2891 has a differential input

sensitivity of 4 mV p-p and accepts up to a 2.0 V p-p differential

input overload voltage. The ADN2891 supports current mode

logic (CML) outputs with controlled rise and fall times.

80 ps rise/fall times

CML outputs: 700 mV p-p differential

Programmable LOS detector: 3.5 mV to 35 mV

Rx signal strength indicator (RSSI)

SFF-8472-compliant average power measurement

Single-supply operation: 3.3 V

Low power dissipation: 145 mW

Available in space-saving 3 mm × 3 mm, 16-lead LFCSP

By monitoring the bias current through a photodiode, the on-

chip RSSI detector measures the average power received with

2% typical linearity over the entire valid input range of the

photodiode. The on-chip RSSI detector facilitates SFF-8472-

compliant optical transceivers by eliminating the need for

external RSSI detector circuitry.

Extended temperature range: −40°C to +95°C

SFP reference design available

APPLICATIONS

SFP/SFF/GBIC optical transceivers

OC-3/OC-12/OC-48, GbE, Fibre Channel (FC) receivers

Additional features include a programmable loss-of-signal

(LOS) detector and output squelch.

10GBASE-LX4 transceivers

WDM transponders

The ADN2891 is available in a 3 mm × 3 mm, 16-lead LFCSP.

FUNCTIONAL BLOCK DIAGRAM

ADN2880

DRVCC

50

Ω

50

Ω

50

Ω

50

Ω

3k

Ω

PIN

NIN

PD_VCC

PD_CATHODE

ADN2891

RSSI/LOS

DETECTOR

0.01

CAZ1

CAZ2

SQUELCH

AVCC

AVEE

DRVCC

DRVEE

THRADJ

OUTP

LOS

10k

Ω

+V

ADuC7020

RSSI_OUT

OUTN

Figure 1.