1.0625Gbps to 10.32Gbps, Integrated, Low-Power SFP+ Limiting Amplifier and VCSEL Driver

The MAX3798 is a highly integrated limiting amplifier and VCSEL driver designed for 1x/2x/4x/8x Fibre Channel transmission systems at data rates up to 8.5Gbps as well as for 10GBASE-SR transmission systems at a data rate of 10.3125Gbps. Operating from a single +3.3V supply, this low-power integrated limiting amplifier and VCSEL driver IC enables a platform design for SFP MSA as well as for SFP+ MSA-based optical transceivers. The high-sensitivity limiting amplifier limits the differential input signal generated by a transimpedance amplifier into a CML-level differential output signal. The compact VCSEL driver provides a modulation and a bias current for a VCSEL diode. The optical average power is controlled by an average power control (APC) loop implemented by a controller that interfaces to the VCSEL driver through a 3-wire digital interface. All differential I/Os are optimally back-terminated for a 50Ω transmission line PCB design.

The use of a 3-wire digital interface reduces the pin count while enabling advanced Rx (mode selection, LOS threshold, LOS squelch, LOS polarity, CML output level, signal path polarity, slew-rate control, deemphasis, and fast mode-select change time) and Tx settings (modulation current, bias current, polarity, programmable deemphasis, eye-crossing adjustment, and eye safety control) without the need for external components. The MAX3798 provides multiple current and voltage DACs to allow the use of low-cost controller ICs.

The MAX3798 is packaged in a lead-free, 5mm x 5mm, 32-pin TQFN package.

Applications

* 10GBASE-LR SFP+ Optical Transceiver (1310nm VCSEL) * 10GBASE-LRM SFP+ Optical Transceiver (1310nm VCSEL) * 10GBASE-SR SFP+ Optical Transceiver * 1x/2x/4x/8x SFF/SFP/SFP+ MSA Fibre Channel (FC) Optical Transceiver

* Low Power Dissipation of 320mW at 3.3V Power Supply

* Up to 10.32Gbps (NRZ) Operation

* 3mVP-P Receiver Sensitivity at 10.32Gbps

* 4psP-P DJ at Receiver Output at 8.5Gbps 8B/10B

* 4psP-P DJ at Receiver Output at 10.32Gbps 231 - 1 PRBS

* 26ps Rise and Fall Time at Rx/Tx Output

* Mode Select for High-Gain Mode and High-Bandwidth Mode

* CML Output Slew-Rate Adjustment for High-Gain Mode

* CML Output with Continuous Level Adjustment

* CML Output Squelch

* Polarity Select for Rx and Tx

* LOS Assert Level Adjustment

* LOS Polarity Select

* Modulation Current Up to 12mA Into 100Ω Differential Load

* Bias Current Up to 15mA

* Integrated Eye Safety Features

* Selectable Deemphasis at Rx Output

* 3-Wire Digital Interface

* Eye-Crossing Adjustment of Modulation Output

* Programmable Deemphasis at Tx Output

* Fast Mode-Select Change Time of 10µs