Analog Devices Inc./Maxim Integrated DS1856E-020+T&R

Overview

DS1856E-020+T&R from Maxim Integrated is a dual, temperature-controlled, nonvolatile variable resistor IC with integrated 12-bit analog monitoring (VCC, MON1–MON3, internal temperature), password-protected EEPROM, and SFF-8472-compliant diagnostics for optical transceivers. It delivers two 256-position linear resistors (20kΩ nominal), factory-calibrated monitors with ±0.5% FS accuracy, and 2-wire serial interface operating from 3.3V or 5V supply across –40°C to +95°C.

For engineers reviewing the DS1856E-020+T&R datasheet, DS1856E-020+T&R pinout, DS1856E-020+T&R application, or DS1856E-020+T&R equivalent, this device serves as a system-level calibration and diagnostic hub in pluggable optical modules-requiring precise resistor temperature compensation, multi-channel voltage/temperature alarm flagging, and secure memory access control.

Technical Context

The DS1856E-020+T&R implements a dual-resistor architecture where each 20kΩ resistor's value is determined by a temperature-indexed look-up table (80h–C7h), updated every 2°C over –40°C to +102°C. Resistor positions are stored in EEPROM and retain settings after power loss.

Its analog monitoring subsystem includes a direct-to-digital temperature sensor (±3.0°C error), four 12-bit ADC channels (VCC, MON1–MON3) with programmable full-scale ranges, and automatic alarm/warning flag generation against user-defined high/low thresholds-all accessible via 2-wire interface at up to 400kHz (Fast-mode).

Key Specifications

Pinout & Package

DS1856E-020+T&R is housed in a 16-pin TSSOP package (4.4mm × 5.0mm, 0.65mm pitch), lead-free and tape-and-reel compatible.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar dual-resistor monitoring applications.

Compared with DS1856E-020+T&R, the DS1856E-050+T&R offers identical functionality at higher resistance, while the DS1859E-020+T&R sacrifices integrated temperature sensing and MON3 to reduce cost and complexity - making DS1856E-020+T&R the optimal choice for SFF-8472-compliant, self-contained calibration in compact optical modules.

Availability

DS1856E-020+T&R is available at Aetrix Electronics and suitable for optical transceivers, RF power amplifiers, instrumentation systems, and industrial control loops requiring stable component supply, long-term calibration retention, and SFF-8472 diagnostic compliance.

Supply support for DS1856E-020+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, designs precision analog and mixed-signal ICs for communications, computing, and industrial applications with emphasis on integration, reliability, and standards compliance.

The DS1856E-020+T&R belongs to Maxim's optical monitoring and calibration product line, engineered specifically to meet SFF-8472 requirements for pluggable transceivers - combining resistive trimming, multi-channel monitoring, and secure memory in a single 16-pin package.

FAQ

What is the resistor tolerance and temperature coefficient of DS1856E-020+T&R?

The DS1856E-020+T&R exhibits ±2 LSB absolute linearity and ±1 LSB relative linearity across its 256 positions. Its temperature coefficient is specified at 50 ppm/°C, measured over the full –40°C to +95°C operating range. Position 00h resistance falls between 0.20kΩ and 0.55kΩ, while position FFh ranges from 15kΩ to 25kΩ at +25°C - all verified per DS1856 datasheet Table "ANALOG RESISTOR CHARACTERISTICS".

Does DS1856E-020+T&R support both 3.3V and 5V supply rails?

Yes, DS1856E-020+T&R operates from 2.85V to 5.5V, fully supporting both 3.3V and 5V systems without external level shifters. Its digital I/O (SDA/SCL) meets VIH ≥ 0.7×VCC and VIL ≤ 0.3×VCC across this range, and analog monitors maintain ±0.5% FS accuracy regardless of supply voltage - confirmed in the "RECOMMENDED OPERATING CONDITIONS" and "DC ELECTRICAL CHARACTERISTICS" sections of the DS1856 datasheet.

How does the temperature compensation mechanism work in DS1856E-020+T&R?

DS1856E-020+T&R uses an internal direct-to-digital temperature sensor to index into two dedicated 72-byte look-up tables (Table 04 for Resistor 0, Table 05 for Resistor 1), each mapping a unique 256-position value to every 2°C increment from –40°C to +102°C. The device automatically selects the appropriate resistor setting based on measured temperature - no host MCU intervention is required once tables are programmed, enabling true autonomous compensation.

Can DS1856E-020+T&R be used without password protection enabled?

Yes, DS1856E-020+T&R defaults to User Access mode at power-up, allowing full read access to monitoring registers (VCC, MON1–MON3, temperature), alarm flags, and resistor position values. Password protection only restricts write access to configuration bytes, thresholds, and EEPROM - all critical monitoring functions remain fully operational without entering PW1 or PW2, as defined in the "Password Protection" section of the DS1856 datasheet.

What is the maximum update rate for monitored parameters in DS1856E-020+T&R?

The DS1856E-020+T&R updates all five monitored channels (VCC, MON1, MON2, MON3, temperature) in round-robin fashion every 47–60ms (tframe), as specified in the "ANALOG VOLTAGE MONITORING" section. This frame rate is fixed and cannot be accelerated; however, alarm/warning flags are asserted within one frame period of an out-of-limit condition, ensuring timely fault response in optical module applications.