Analog Devices Inc./Maxim Integrated MXD1815UR31+T

Overview

MXD1815UR31+T from Maxim Integrated is a precision low-power microprocessor reset supervisor IC designed for +2.5V/+3.0V/+3.3V digital systems. It provides active-low, open-drain RESET output with factory-trimmed 3.06V reset threshold (±2.5% over temperature), 100ms minimum reset timeout, and operates down to VCC = +1.0V. It is used in portable battery-powered equipment to ensure reliable power-on reset and brownout protection.

For engineers reviewing the MXD1815UR31+T datasheet, MXD1815UR31+T pinout, MXD1815UR31+T application, or MXD1815UR31+T equivalent, key selection criteria include its 3.06V threshold accuracy, 4µA supply current at 3.6V, SOT23-3 package compatibility, and open-drain output with internal 5.5kΩ pullup - critical for interfacing with bidirectional μP reset pins.

Technical Context

The MXD1815UR31+T integrates a precision voltage comparator monitoring VCC against a factory-set 3.06V threshold, with built-in hysteresis and transient immunity to suppress false resets from sub-µs VCC glitches. Its internal timer guarantees ≥100ms reset assertion after VCC rises above threshold, independent of supply ramp rate.

As an open-drain, active-low supervisor, it interfaces directly with microcontrollers requiring external pullup or bidirectional reset handling (e.g., Motorola 68HC11), eliminating need for external resistors. It supports full operation from -40°C to +105°C and maintains valid RESET logic state down to VCC = +1.0V.

Key Specifications

Pinout & Package

MXD1815UR31+T is housed in a 3-pin SOT23 package (JEDEC TO-236AB), with 1.3mm × 2.9mm footprint, 0.95mm height, and gull-wing leads. Pin 1 is RESET (open-drain active-low), Pin 2 is VCC (supply and threshold monitor input), and Pin 3 is GND.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar microprocessor reset supervision applications.

Compared with MXD1815UR31+T, MAX6326UR31+T offers lower quiescent current but sacrifices open-drain interoperability, while TPS3808G33DBVR delivers superior threshold precision at the cost of added external components and reduced low-VCC robustness.

Availability

MXD1815UR31+T is available at Aetrix Electronics and suitable for portable medical monitors, industrial PLC I/O modules, smart meter communication units, and wireless sensor node gateways requiring stable component supply across extended temperature and long product lifecycles.

Supply support for MXD1815UR31+T 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 high-performance analog, mixed-signal, and power management ICs for industrial, communications, and consumer applications.

The MXD1815UR31+T belongs to Maxim's μP reset supervisor product line, engineered for ultra-low-power, precision voltage monitoring in battery-critical and thermally demanding embedded systems.

FAQ

What is the exact reset threshold voltage of MXD1815UR31+T and how tightly is it specified?

The MXD1815UR31+T has a factory-set reset threshold of 3.06V, guaranteed over temperature with ±2.5% accuracy (2.98V to 3.15V) across -40°C to +105°C. This value is laser-trimmed during production and documented in the Electrical Characteristics table under VTH for suffix R31. The MXD1815UR31+T does not require external calibration or adjustment.

Does MXD1815UR31+T include an internal pullup resistor, and what is its nominal value?

Yes, MXD1815UR31+T features an internal pullup resistor on its open-drain RESET pin, with a nominal value of 5.5kΩ (range 3.5kΩ to 7.5kΩ). This eliminates the need for an external pullup when interfacing with microcontrollers that accept open-drain reset inputs, such as the Motorola 68HC11. The MXD1815UR31+T datasheet confirms this in the Electrical Characteristics section under "Internal Pullup Resistor, Open-Drain".

Can MXD1815UR31+T operate reliably when VCC falls below 2.0V?

Yes, MXD1815UR31+T is guaranteed to maintain valid RESET logic state down to VCC = +1.0V, per Absolute Maximum Ratings and Electrical Characteristics. Its internal comparator and timer remain functional, and the open-drain output correctly asserts or deasserts reset even at 1.0V. This behavior is explicitly confirmed for MXD1815UR31+T in the General Description and Electrical Characteristics tables.

What is the minimum reset timeout period for MXD1815UR31+T, and is it fixed or adjustable?

The MXD1815UR31+T provides a fixed minimum reset timeout period of 100ms after VCC rises above the 3.06V threshold. This value is internally generated and non-adjustable; typical values range from 100ms to 250ms depending on temperature and supply conditions. The MXD1815UR31+T does not support external capacitor timing or programmable delay.

Is MXD1815UR31+T pin-compatible with other members of the MXD181x family, and which packages does it use?

Yes, MXD1815UR31+T uses the standard 3-pin SOT23-3 package (U3-1 outline), making it pin-compatible with all MXD181x variants in the U-suffix configuration, including MXD1810URxx+T through MXD1818URxx+T. Footprint and solder pad layout are identical; only reset threshold and output type differ across the family. The MXD1815UR31+T shares the same land pattern (90-0179) and mechanical dimensions.