3.3 V, 4.25 Gbps,

Limiting Amplifier

Data Sheet

ADN2892

Rev. C

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FEATURES

Input sensitivity: 3.5 mV p-p

70 ps rise/fall times

CML outputs: 750 mV p-p differential

Bandwidth selectable for multirate 1×/2×/4× FC modules

Optional LOS output inversion

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: 160 mW

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

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

SFP reference design available

APPLICATIONS

1×, 2×, and 4× FC transceivers

SFP/SFF/GBIC optical transceivers

GbE transceivers

Backplane receivers

GENERAL DESCRIPTION

The ADN2892 is a 4.25 Gbps limiting amplifier with integrated

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

strength indicator (RSSI). This part is optimized for Fibre

Channel (FC) and Gigabit Ethernet (GbE) optoelectronic

conversion applications. The ADN2892 has a differential input

sensitivity of 3.5 mV p-p and accepts up to a 2.0 V p-p

differential input overload voltage. The ADN2892 has current

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

The ADN2892 has a selectable low-pass filter with a −3 dB

cutoff frequency of 1.5 GHz. By setting BW_SEL to Logic 0, the

filter can limit the relaxation oscillation of a low cost CD laser

used in a legacy 1 Gbps FC transmitter. The limited BW also

reduces the rms noise and in turn improves the receiver optical

sensitivity for a lower data rate application, such as 1× FC and

GbE.

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.

Additional features include a programmable loss-of-signal

(LOS) detector and output squelch. The ADN2892 is available

in a 3 mm × 3 mm, 16-lead LFCSP.

FUNCTIONAL BLOCK DIAGRAM

LPF

ADN2892

AVCC

AVEE

BW_SEL

SQUELCH

DRVCC

DRVEE

RSSI/LOS

DETECTOR

ADN2882

OUTP

OUTN

PIN

NIN

50

Ω

50

Ω

3.5k

Ω

50

Ω

50

Ω

PD_VCC

PD_CATHODE

LOS

RSSI_OUT

V+

10k

Ω

ADuC7020

THRADJ

LOS_INV

Figure 1. RSSI Function Capable—Applications Setup Block Diagram