3.3 V, 4.25 Gbps,
Data Sheet
Rev. C Document Feedback
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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
50Ω
50Ω
3.5kΩ
V
REF
50Ω
50Ω
PD_VCC
PD_CATHODE
LOS
RSSI_OUT
V+
10kΩ
ADuC7020
THRADJ
LOS_INV
04986-001
Figure 1. RSSI Function Capable—Applications Setup Block Diagram
