Analog Devices Inc./Maxim Integrated DS1877T+T&R

Overview

DS1877T+T&R from Maxim Integrated is a dual-receiver SFP controller IC designed for SFF-8472-compliant optical transceiver modules. It integrates four ADC channels (temperature, VCC, RSSI1, RSSI2), two 10-bit delta-sigma DACs with 72-entry temperature-indexed LUTs, and comprehensive LOS detection for two independent Rx channels - enabling full digital monitoring and control in compact SFP/SFP+ pluggable modules used in fiber-optic datacom systems.

For engineers reviewing the DS1877T+T&R datasheet, DS1877T+T&R pinout, DS1877T+T&R application, or DS1877T+T&R equivalent, this device delivers SFF-8472 compliance, dual-channel RSSI monitoring with differential inputs, I²C interface at up to 400kHz, -40°C to +95°C operation, and 28-pin TQFN-EP packaging - critical for high-density, thermally constrained SFP module designs requiring precise analog telemetry and fault signaling.

Technical Context

The DS1877T+T&R implements a shared 13-bit ADC with round-robin sampling across four analog inputs (internal temp sensor, VCC, RSSI1, RSSI2), each with programmable full-scale range and offset. Its dual quick-trip comparators independently monitor RSSI1 and RSSI2 against user-defined thresholds to assert LOS1/LOS2 and drive LOSOUT.

It features two independent 10-bit delta-sigma DAC outputs (DAC1/DAC2) referenced to REFIN, each controlled by a dedicated 72-entry temperature LUT for closed-loop calibration. Communication occurs via I²C at standard/fast mode (up to 400kHz), with slave addresses at A0h (auxiliary EEPROM), A2h (Rx1), and B2h (Rx2) - enabling discrete channel access within dual-Rx SFP architecture.

Key Specifications

Pinout & Package

DS1877T+T&R is housed in a 28-pin thin quad flat no-lead package with exposed pad (TQFN-EP, 5mm × 5mm × 0.75mm), RoHS-compliant and lead-free. The exposed pad must be connected to GND for thermal and electrical performance.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar SFP controller applications.

Compared with MAX3665ETL+, DS1877T+T&R adds dual-Rx telemetry, LUT-based DACs, and multi-address I²C - enabling true channel-isolated control. Against DS1878T+T&R, it omits CDR circuitry, reducing BOM cost and power while retaining full SFF-8472 monitoring fidelity for 1G/2.5G/4G applications.

Availability

DS1877T+T&R is available at Aetrix Electronics and suitable for SFP module manufacturing, optical transceiver design, and industrial fiber-optic sensor integration requiring stable component supply, full SFF-8472 compliance, and extended temperature operation.

Supply support for DS1877T+T&R includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Maxim Integrated (now part of Analog Devices) is a semiconductor company specializing in precision analog, mixed-signal, and power management ICs for industrial, communications, and computing applications.

The DS1877T+T&R belongs to Maxim's SFP/SFP+ controller product line, engineered specifically to meet SFF-8472 Rev 12.2 requirements for dual-receiver optical modules - emphasizing telemetry accuracy, fault response speed, and secure configuration in space- and thermal-constrained pluggable form factors.

FAQ

What is the primary function of the DS1877T+T&R in an SFP module?

The DS1877T+T&R serves as the core digital controller and analog monitor for dual-receiver SFP/SFP+ modules. It implements full SFF-8472 compliance by digitizing temperature, VCC, and two differential RSSI inputs via a 13-bit ADC; generating two temperature-compensated 10-bit DAC outputs; detecting loss-of-signal on both receivers; and communicating with the host via I²C at addresses A2h and B2h. Its design enables complete telemetry and control without external analog components.

Does the DS1877T+T&R support differential RSSI inputs, and what is their voltage range?

Yes, the DS1877T+T&R supports two fully differential analog inputs: RSSI1P/N (Pins 14/17) and RSSI2P/N (Pins 12/13). Each pair has a common-mode input range from GND to VCC and a full-scale differential range of 1.25V. The inputs are high-impedance (35–65kΩ) and support both internal and external calibration - allowing direct connection to ROSA outputs without signal conditioning.

How does the DS1877T+T&R handle temperature compensation for its DAC outputs?

The DS1877T+T&R uses two independent 72-entry lookup tables (LUTs), one for DAC1 and one for DAC2, each indexed by the on-die temperature sensor reading. During operation, the device reads the temperature, selects the corresponding LUT entry, and applies that digital value to the delta-sigma modulator. This enables precise, real-time compensation of laser bias or TIA gain drift across the -40°C to +95°C range - critical for maintaining optical power stability in uncooled SFP modules.

What I²C slave addresses does the DS1877T+T&R use, and why are multiple addresses needed?

The DS1877T+T&R uses three I²C slave addresses: A0h (256-byte auxiliary EEPROM), A2h (Rx1 telemetry and control registers), and B2h (Rx2 telemetry and control registers). This multi-address architecture allows the host microcontroller to access channel-specific data (e.g., RSSI1 vs. RSSI2 thresholds, DAC1 vs. DAC2 LUTs) independently - essential for synchronized dual-Rx operation and avoiding register contention in time-critical SFP applications.

Is the DS1877T+T&R pin-compatible with other Maxim SFP controllers like the DS1878?

Yes, the DS1877T+T&R is pin-compatible with the DS1878T+T&R - both use the identical 28-pin TQFN-EP (5mm × 5mm) package and share identical pin functions, power requirements, and I²C interface behavior. However, the DS1878 adds integrated 10GbE CDR functionality and extended memory mapping for SFP+; the DS1877T+T&R omits CDR to reduce cost and power for applications where CDR is implemented externally or unnecessary.