MAX3945ETE+T

Overview

The MAX3945ETE+T is a +3.3V, multirate limiting amplifier designed for Fibre Channel and Ethernet transmission systems operating at data rates from 1.0625Gbps to 11.3Gbps. It converts transimpedance amplifier signals into CML-level differential outputs with optimal back-termination for 50Ω PCB traces. The device features dual-path limiting with programmable filtering to optimize sensitivity and suppress relaxation oscillations. It incorporates two loss-of-signal circuits and a programmable time mask. A 3-wire digital interface enables control of LOS threshold, polarity, output level, and input filters without external components.

Feature Summary

• Dual-path architecture supports low-rate (1.0625Gbps to 4.25Gbps) and high-rate (up to 11.3Gbps) operation with selectable input filters
• Integrated 3-wire digital interface controls LOS parameters, CML output levels, deemphasis, and polarity settings
• Programmable loss-of-signal detection offers both Rx input-based and RSSI monitor-based modes with adjustable thresholds
• Low power dissipation of 130mW enables single-module design compliance with SFP+ specifications

Applications

• 1x/2x/4x/8x SFF/SFP/SFP+ MSA Fibre-Channel Optical Transceiver
• 10GBASE-SR/LR SFP+ Optical Transceiver
• 10G PON ONU

Procurement Notes

Verify the specific ordering suffix against the manufacturer's current documentation to ensure correct temperature range and package configuration. Confirm that the exposed pad connection requirements are met during assembly to maintain thermal performance and electrical grounding as specified in the datasheet.

Selection Notes

Select this component when designing optical transceivers requiring support for multiple data rates up to 11.3Gbps. Ensure the system design accommodates the 3mm x 3mm 16-pin TQFN package dimensions and provides adequate thermal relief for the exposed pad. Verify compatibility with the host controller's 3-wire interface timing specifications.

Part Context

This part belongs to the Maxim Integrated family of high-speed optical receiver amplifiers. It is specifically engineered to complement laser drivers in transmit/receive chipsets for short-reach and long-reach optical networking applications. The device addresses the need for flexible signal conditioning in dense small form-factor pluggable modules.

Replacement Considerations

No official substitute part numbers are confirmed in the provided documentation.

FAQ

How is the offset-correction loop configured?

An external capacitor connected between the CAZ pin and ground sets the cutoff frequency. It is approximately 2kHz when RATE_SEL = 0 and 0.7kHz when RATE_SEL = 1. The loop can be disabled via the digital interface.

What are the two modes for Loss-of-Signal detection?

The MAX3945 supports Rx input-based LOS detection, which compares differential input amplitude against a threshold, and RSSI monitor-based LOS detection, which compares the voltage at the RPMIN pin against a threshold.

How does the device handle false LOS signals after light loss?

A programmable LOS output masking time feature masks false input signals caused by glitches or relaxation oscillations. This time can be set from 0 to 4500Fs in 35Fs steps using the SET_LOSTIMER register.