Analog Devices Inc./Maxim Integrated DS1841X

Overview

DS1841X from Maxim Integrated is a 7-bit, nonvolatile, I²C-compatible logarithmic digital resistor with integrated temperature sensor and 72-byte NV lookup table (LUT), delivering temperature-compensated resistance from 3.7kΩ to 22kΩ across -40°C to +100°C. It features 128 wiper tap points, 3.6kΩ fixed series resistor (RS), and operates from 2.7V to 5.5V supply for optical transceiver bias control and linear compensation circuits.

For engineers reviewing the DS1841X datasheet, DS1841X pinout, DS1841X application, or DS1841X equivalent, key selection considerations include its LUT-driven wiper update mode, signed/unsigned LUT value handling in Adder vs. LUT Mode, I²C slave address configuration via A0/A1 pins, and guaranteed ±5°C temperature sensor accuracy over full industrial range.

Technical Context

The DS1841X implements dual operational modes-LUT Mode and LUT Adder Mode-selected by Control Register 1 bits (Update Mode = 1, Adder Mode = 0 or 1). In LUT Mode, the wiper register (WR) loads only the LUTVAL indexed by internal temperature; in LUT Adder Mode (default), WR loads LUTVAL + IVR with signed two's complement LUT entries enabling offset compensation.

Its on-chip 8-bit temperature sensor provides 1°C resolution in signed two's complement format, updated every 16ms (tFRAME), and drives a 72-byte NV LUT covering -40°C to +100°C in ~2°C windows with 1°C hysteresis per slot. The I²C interface supports Fast-Mode up to 400kHz and allows up to four devices on one bus via A0/A1 address pins.

Key Specifications

Pinout & Package

DS1841X is housed in a 3mm × 3mm, 10-pin TDFN-EP package with exposed paddle (EP) requiring connection to GND. Pin 9 (N.C.) is unconnected; EP must be soldered to ground plane for thermal and electrical integrity.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar temperature-compensated resistor applications.

Compared with DS1841X, MAX5477 lacks autonomous temperature-driven operation and demands external sensing and processing, while AD5175 provides sensor data but no built-in LUT execution-both require significant firmware overhead that DS1841X eliminates via hardware-accelerated closed-loop compensation.

Availability

DS1841X is available at Aetrix Electronics and suitable for optical transceivers, DC-DC converter feedback networks, instrumentation gain stages, and laser diode bias control requiring stable component supply with guaranteed long-term availability and traceable sourcing.

Supply support for DS1841X 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, mixed-signal, and digital ICs for industrial, communications, and computing applications.

The DS1841X belongs to Maxim's temperature-aware programmable resistor product line, engineered specifically to replace mechanical potentiometers in thermally sensitive analog control loops without MCU dependency.

FAQ

What is the default operating mode of the DS1841X after power-up?

The DS1841X powers up in LUT Adder Mode (Update Mode = 1, Adder Mode = 1) as configured in factory-default Control Register 1 (03h = 03h). In this mode, the wiper register (WR) loads the sum of the Initial Value Register (IVR) and the LUT value (LUTVAL) indexed by temperature. This enables signed offset compensation and is ideal for applications requiring baseline resistance adjustment plus thermal drift correction. The DS1841X remains in this mode until explicitly reconfigured via I²C writes to CR1.

How does the DS1841X handle temperature hysteresis in its LUT indexing?

The DS1841X implements 1°C hysteresis per 2°C temperature window in its 72-byte LUT (addresses 80h–C7h) to prevent wiper chattering near boundary temperatures. For example, if the measured temperature crosses from -38°C to -37°C, the LUTAR index transitions only after crossing the hysteresis threshold-e.g., from -38°C to -36°C-ensuring stable wiper positioning during slow thermal drift. This behavior is hardwired and requires no configuration; the DS1841X automatically applies hysteresis during each tFRAME (16ms) temperature conversion cycle.

Can the DS1841X be used without programming its NV LUT?

Yes, the DS1841X functions immediately after power-up using factory-default LUT contents (all 00h) and IVR = 00h. In LUT Mode, this results in a fixed wiper position (00h) regardless of temperature; in LUT Adder Mode, it yields WR = 00h + 00h = 00h. To enable temperature compensation, the LUT must be programmed via I²C with application-specific resistance-vs-temperature profiles. The DS1841X supports full NV LUT writes at any time, and changes persist through power cycles-no external memory or host intervention is needed once programmed.

What is the maximum allowable current through the RW terminal of the DS1841X?

The DS1841X specifies a maximum wiper current (IWIPER) of 3mA under steady-state conditions, with absolute maximum rating of 3mA. Exceeding this limit risks resistor element degradation or parametric shift. The device guarantees 2mA wiper current capability across full temperature and voltage range. When used in feedback networks driving op-amps or DC-DC error amplifiers, ensure total current through RW–RGND path-including bias currents and leakage-stays below 2mA for long-term reliability. The DS1841X datasheet confirms IWIPER = 2mA (typical) and 3mA (max) in DC Electrical Characteristics.

Does the DS1841X support standard I²C repeated START conditions?

Yes, the DS1841X fully supports I²C repeated START conditions as defined in the I²C specification. Its SDA and SCL interfaces comply with Fast-Mode timing requirements, including tHD:STA ≥ 0.6μs and tSU:STA ≥ 0.6μs, enabling seamless integration into multi-byte read sequences-such as reading both Temperature Result (0Ch) and Supply Voltage (0Eh) registers in one transaction. Repeated STARTs are essential for efficient register access without bus release, and the DS1841X acknowledges them identically to standard STARTs, ensuring compatibility with all standard I²C masters and protocol analyzers.