3.3 V 4.25 Gb/s Limiting Amplifier

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 BWSEL 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 onchip 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.

Applications

* 1×, 2×, and 4× FC transceivers

* SFP/SFF/GBIC optical transceivers

* GbE transceivers

* Backplane receivers

* 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