Analog Devices Inc./Maxim Integrated DS1875RT+

Overview

DS1875RT+ from Maxim Integrated is a PON triplexer and SFP controller IC designed for burst-mode optical transceivers. It integrates APC loop control, temperature-indexed laser bias/modulation DACs, 10-channel ADC monitoring (including internal temperature sensor), four DAC outputs, PWM-based APD bias generation up to 90V, and full SFF-8472 diagnostics - enabling compact, compliant BPON/GPON/EPON triplexer modules.

For engineers reviewing the DS1875RT+ datasheet, DS1875RT+ pinout, DS1875RT+ application, or DS1875RT+ equivalent, this page delivers verified functional role, validated pin assignments, confirmed operating range (–40°C to +95°C), real-world diagnostic capabilities (RSSI with 29dB electrical dynamic range), and precise alternative part guidance for optical module design.

Technical Context

The DS1875RT+ implements dual closed-loop control: one APC loop using BMD input with factory-calibrated lookup tables for laser bias and modulation current vs. temperature, and a separate PWM-controlled feedback loop for APD bias with selectable switching frequencies (131.25/262.5/525/1050 kHz) and boost/buck capability. Its analog monitoring architecture supports simultaneous sampling of eight external voltage inputs (MON1–MON8), VCC, and internal die temperature with 13-bit ADC resolution and programmable full-scale ranges.

It features I²C-compatible interface (400 kHz fast-mode) with password-protected nonvolatile memory (120 bytes at main address, 128 bytes protected by second password, plus 256 bytes at A0h slave address), maskable fault shutdown via TX-F and FETG outputs, and comprehensive quick-trip alarm detection on MON3 with hysteresis configuration - all synchronized to burst-enable timing (BEN) for PON compliance.

Key Specifications

Pinout & Package

DS1875RT+ is housed in a 38-pin TQFN package (5mm × 7mm × 0.8mm) with exposed thermal pad (EP). The package supports high-density optical module layouts and efficient heat dissipation during APD bias generation.

Key Features

Applications

Equivalent & Alternatives

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

Compared with DS1875RT+, the DS1873 offers fewer monitoring resources and lower diagnostic fidelity, while the MAX3643 serves only as a companion driver - neither provides full functional equivalence, making DS1875RT+ the sole integrated solution for new SFP/PON triplexer designs requiring complete burst-mode control and SFF-8472 compliance.

Availability

DS1875RT+ is available at Aetrix Electronics and suitable for BPON/GPON/EPON optical triplexers, SFP/SFP+ transceiver modules, APD bias controllers, and laser safety monitoring systems requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.

Supply support for DS1875RT+ 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 communications, computing, and industrial applications.

The DS1875RT+ belongs to Maxim's optical networking controller product line, engineered specifically to integrate burst-mode timing, laser/APD control, and SFF-8472 diagnostics into compact pluggable modules for passive optical networks.

FAQ

What is the primary function of the DS1875RT+ in optical transceiver modules?

The DS1875RT+ serves as a fully integrated PON triplexer and SFP controller IC. It manages laser bias and modulation via APC loops with temperature lookup tables, generates APD bias using a configurable PWM controller, monitors 10 analog signals (including internal temperature), and implements full SFF-8472 diagnostic functionality - all in a single 38-pin TQFN package. This eliminates the need for multiple discrete components in BPON/GPON/EPON modules.

Does the DS1875RT+ support both boost and buck configurations for APD bias generation?

Yes, the DS1875RT+ PWM controller supports both boost and buck modes for APD bias generation. In boost mode, it can generate up to 90V bias using optional external components (inductor, diode, capacitor). The switching frequency is selectable among 131.25kHz, 262.5kHz, 525kHz, or 1050kHz to optimize efficiency and transient response. Feedback (FB) and compensation (COMP) pins enable stable closed-loop regulation in either topology.

How does the DS1875RT+ ensure compliance with SFF-8472 diagnostic requirements?

The DS1875RT+ natively implements all mandatory SFF-8472 diagnostic functions: real-time monitoring of temperature, VCC, TX bias, TX output power, and RX input power via its 10-channel ADC and RSSI circuitry; I²C interface for host communication; and standardized memory map with alarm/warning flags. Its factory-calibrated internal temperature sensor (±3.0°C error), 29dB RSSI dynamic range, and maskable fault outputs (TX-F, FETG) meet specification requirements for digital diagnostic monitoring interfaces.

What are the memory protection features of the DS1875RT+?

The DS1875RT+ includes three tiers of password-protected nonvolatile memory: 120 bytes protected by Password-1, 128 bytes protected by Password-2 in the main device address, and 256 additional bytes located at the A0h slave address. These regions store calibration data, vendor-specific settings, and operational parameters. Access requires correct password entry via I²C, preventing unauthorized modification of critical coefficients used in APC, modulation, and RSSI calculations.

Can the DS1875RT+ operate across the full industrial temperature range without derating?

Yes, the DS1875RT+ is fully specified and tested for continuous operation from –40°C to +95°C. All key parameters - including ADC accuracy (±0.50%FS), DAC error (±1.25%FS), thermometer error (±3.0°C), supply current (5.5–10mA), and I²C timing - are guaranteed across this range. The device uses internal factory calibration and temperature-indexed LUTs to maintain performance without external compensation or firmware adjustment.