Analog Devices Inc./Maxim Integrated MAX1818EUT25+T

Overview

The MAX1818EUT25+T from Maxim Integrated is a 2.5V fixed-output, 500mA low-dropout linear regulator featuring ±1% output voltage accuracy, 120mV dropout at full load, and 125μA ground current independent of load. It integrates an active-low open-drain POK (power-ok) output, 0.1μA shutdown current, thermal shutdown at +170°C, and short-circuit protection. Designed for space-constrained portable systems, it powers core logic rails in notebook computers and USB hubs where stable low-voltage regulation under battery droop is critical.

For engineers reviewing the MAX1818EUT25+T datasheet, MAX1818EUT25+T pinout, MAX1818EUT25+T application, or MAX1818EUT25+T equivalent, key selection criteria include guaranteed 500mA output with <120mV dropout at 2.5V output, preset 2.5V operation without external resistors, SOT23-6 package thermal limits (800mW at +70°C), and POK threshold at 93% of nominal VOUT for microcontroller power sequencing.

Technical Context

The MAX1818EUT25+T employs an internal P-channel MOSFET pass transistor with 0.25Ω R_DS(ON), enabling low dropout and eliminating base-drive current loss typical of PNP-based regulators. Its Dual Mode™ architecture selects between factory-trimmed 2.5V output (SET tied to GND) and adjustable mode via external resistor divider (SET floating).

Regulation relies on a 1.25V internal reference compared against feedback from either internal resistive divider (for preset mode) or external SET node. The POK output asserts low when V_OUT falls below 93% of 2.5V (i.e., 2.325V), with open-drain N-channel structure requiring external pull-up to OUT or V_OUT.

Key Specifications

Pinout & Package

Package: 6-pin SOT23-6 (U6F-6), 800mW power dissipation at +70°C, RoHS-compliant.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar low-dropout linear regulator applications.

Compared with TPS76325DBVR and MCP1825-2502E/DB, the MAX1818EUT25+T uniquely combines 500mA capability, 120mV dropout, integrated POK, and shutdown control in a 6-pin SOT23-enabling higher efficiency, tighter sequencing, and smaller solution size in battery-critical portable designs.

Availability

MAX1818EUT25+T is available at Aetrix Electronics and suitable for notebook computers, USB hubs, cellular telephones, base stations, and docking stations requiring stable component supply across industrial temperature ranges (-40°C to +85°C).

Supply support for MAX1818EUT25+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) designs precision analog, mixed-signal, and power management ICs for demanding industrial, communications, and consumer applications.

The MAX1818 product line delivers ultra-low-quiescent-current LDOs with integrated power monitoring for battery-powered portable electronics, emphasizing extended runtime, small footprint, and robust fault protection.

FAQ

What output voltage does the MAX1818EUT25+T deliver, and how is it set?

The MAX1818EUT25+T delivers a factory-trimmed, fixed 2.5V output with ±1% accuracy at 100mA and ±3% over full temperature and load range. This is achieved by tying the SET pin to GND, selecting the internal feedback divider. No external resistors are required. The "25" suffix in MAX1818EUT25+T explicitly denotes the 2.5V preset configuration per Maxim's Selector Guide.

Does the MAX1818EUT25+T include power-good monitoring, and how does it interface?

Yes, the MAX1818EUT25+T features an active-low open-drain POK (power-ok) output on Pin 2. It asserts low when V_OUT falls below 93% of nominal (2.325V) and goes high-impedance when regulation is restored. To generate a logic-high signal, connect a 100kΩ pull-up resistor from POK to OUT. This allows direct interfacing with microcontroller reset or interrupt inputs without additional level-shifting circuitry.

What is the maximum continuous output current and thermal limit of the MAX1818EUT25+T?

The MAX1818EUT25+T guarantees 500mA RMS output current. Its thermal protection activates at +170°C junction temperature with +20°C hysteresis, causing pulsed output during sustained overload. At +70°C ambient, the SOT23-6 package dissipates up to 800mW; derating is 10mW/°C above +70°C. For continuous 500mA operation at 2.5V output, VIN must remain ≤ 3.0V to stay within safe power limits.

How does the shutdown function work on the MAX1818EUT25+T, and what is its current draw?

The MAX1818EUT25+T enters ultra-low-power shutdown when the SHDN pin (Pin 3) is pulled low. In this state, the output disconnects from the input, OUT becomes high-impedance, POK is forced low, and total supply current drops to 0.1μA maximum. SHDN accepts voltages up to +6V regardless of VIN or VOUT, simplifying interface with higher-voltage system supervisors. Normal operation resumes when SHDN is pulled high (≥1.6V).

What capacitor values and types are required for stable operation of the MAX1818EUT25+T?

For stable operation, the MAX1818EUT25+T requires a 1μF ceramic capacitor between IN and GND, and a 3.3μF low-ESR (<0.1Ω) ceramic capacitor between OUT and GND. For 2.5V output, the 3.3μF value is sufficient; use 4.7μF for outputs below 2.0V. These capacitors must be placed as close as possible to the respective pins to minimize trace inductance. Larger values (e.g., 10μF) improve PSRR and transient response but are not mandatory for basic stability.