General Description

The MAX3945 is a +3.3V, multirate, low-power limiting amplifier optimized for Fibre Channel and Ethernet transmission systems at data rates up to 11.3Gbps. The high sensitivity limiting amplifier limits the signal generated by a transimpedance amplifier into a CML-level differential output signal. All differential inputs and outputs (I/O) are optimally back terminated for 50I transmission line PCB design. The MAX3945’s dual-path limiting amplifier has programmable filtering to optimize sensitivity for different data rates and to suppress relaxation oscillations that could occur in some optical systems. The MAX3945 incorporates two loss-of-signal (LOS) circuits and a programmable time mask for the LOS output. A 3-wire digital interface reduces the pin count and enables control of LOS threshold, LOS polarity, LOS mode, CML output level, input offset correction, receive (Rx) polarity, Rx input filter, and Rx deemphasis without the need for external components.

The MAX3945 is packaged in a 3mm x 3mm, 16-pin TQFN package.

Features

♦ 130mW Power Dissipation Enables < 1W SFP+ Modules

♦ Enables Single-Module Design Compliance

   with 1000BASE-SX/LX and 10GBASE-SR/LR Specifications

♦ -25.3dBm Optical Sensitivity at 1.25Gbps Using a 10.32Gbps ROSA

♦ Selectable 1GHz/2.1GHz/2.5GHz/3GHz Input Filters at RATE_SEL = 0 Setting

♦ Supports SFF-8431 SFP+ MSA and SFF-8472 Digital Diagnostic

♦ Total Power Dissipation of 130mW at 3.3V Power Supply with RSSI Monitor-Based LOS

♦ Total Power Dissipation of 154mW at 3.3V Power Supply with Rx Input-Based LOS

♦ 4mVP-P Input Sensitivity at 11.3Gbps

♦ 4psP-P DJ at 11.3Gbps with RATE_SEL = 1

♦ 4psP-P DJ at 8.5Gbps with RATE_SEL = 1

♦ 5psP-P DJ at 4.25Gbps with RATE_SEL = 0, BW1 = 1, BW0 = 1

♦ 9.0psP-P DJ at 1.25Gbps with RATE_SEL = 0, BW1 = 0, BW0 = 0

♦ 26ps Rise and Fall Time with RATE_SEL = 1

♦ 52ps Rise and Fall Time with RATE_SEL = 0

♦ CML Output with Level Adjustment and Squelch Mode

♦ Programmable CML Output Deemphasis

♦ CML Output Polarity Select

♦ LOS Polarity Select

♦ Programmable Masking Time for the LOS Output

♦ LOS Assert/Deassert Level Adjustment

♦ Choice of Rx Input-Based LOS or RSSI Monitor Based LOS

♦ 3-Wire Digital Interface Compatible with Maxim’s SFP+ Family of Products

Applications

   1x/2x/4x/8x SFF/SFP/SFP+ MSA Fibre-Channel

   Optical Transceiver

   10GBASE-SR/LR SFP+ Optical Transceiver

   10G PON ONU