Analog Devices Inc./Maxim Integrated MAX1806EUA25+T

Overview

MAX1806EUA25+T from Maxim Integrated is a 2.5V fixed-output, 500mA low-dropout linear regulator with ±1% output voltage accuracy, 175mV dropout at full load, and 210μA ground current. It features an active-low power-OK (POK) output, 0.02μA shutdown current, and thermal/short-circuit protection. Designed for space-constrained portable systems, it powers core logic rails in USB hubs and docking stations.

For engineers reviewing the MAX1806EUA25+T datasheet, MAX1806EUA25+T pinout, MAX1806EUA25+T application, or MAX1806EUA25+T equivalent, key selection criteria include guaranteed 500mA output under 175mV dropout, preset 2.5V output with ±1% accuracy over -40°C to +85°C, POK monitoring capability, and compatibility with 1μF input / 10μF low-ESR output capacitors.

Technical Context

The MAX1806EUA25+T integrates a P-channel MOSFET pass transistor with 0.4Ω R_DS(ON), enabling low dropout and eliminating base-drive current loss typical of PNP-based regulators. Its dual-mode feedback architecture automatically selects internal preset regulation (2.5V) when SET is grounded, using a precision 800mV reference and error amplifier.

Power-OK functionality relies on a comparator monitoring V_OUT against 93% of nominal voltage, driving an open-drain POK output that requires an external 100kΩ pullup to OUT. Thermal shutdown activates at +170°C with 20°C hysteresis, and current limiting caps output at 1.4A typical during short-circuit events.

Key Specifications

Pinout & Package

The MAX1806EUA25+T uses an 8-pin Power-μMAX package (1.3W rating) with an exposed metal thermal pad on the underside for enhanced heat dissipation. The package requires soldering the pad and Pin 5 (GND) to a large PCB ground plane or thermal via array.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TPS76325DBVR and MCP1702T-2502E/MB, the MAX1806EUA25+T delivers 100% higher output current with 40% lower dropout and integrated POK monitoring-enabling single-chip power management for demanding 2.5V rails where reliability and headroom are critical.

Availability

MAX1806EUA25+T is available at Aetrix Electronics and suitable for notebook computers, USB hubs, and docking stations requiring stable component supply, long-term manufacturability, and RoHS-compliant packaging.

Supply support for MAX1806EUA25+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 industrial, communications, computing, and consumer applications.

The MAX1806 belongs to Maxim's μMAX low-dropout regulator family, engineered for portable electronics requiring high output current, ultra-low quiescent current, and compact packaging in battery-powered systems.

FAQ

What is the maximum input voltage for the MAX1806EUA25+T?

The MAX1806EUA25+T supports an absolute maximum input voltage of +6V on IN and SHDN pins, but its operational input range is +2.25V to +5.5V. Exceeding +5.5V may trigger undervoltage lockout or cause permanent damage. For reliable 2.5V output regulation, VIN must remain ≥2.675V (2.5V + 175mV dropout) across all load and temperature conditions. The device includes input undervoltage lockout (1.85V to 2.15V threshold) to prevent unstable startup.

Does the MAX1806EUA25+T require external components to operate in fixed 2.5V mode?

Yes, the MAX1806EUA25+T requires two external capacitors for stable operation in fixed 2.5V mode: a 1μF ceramic capacitor between IN and GND, and a 10μF low-ESR (≤0.1Ω) capacitor between OUT and GND. The SET pin must be connected to GND to activate preset mode. No resistors or additional circuitry are needed-the 2.5V output is factory-trimmed and internally regulated. Placement of both capacitors within 5mm of their respective pins is critical for transient response and PSRR performance.

How does the POK output function on the MAX1806EUA25+T?

The POK output on the MAX1806EUA25+T is an open-drain N-channel driver that pulls low when V_OUT falls below 93% of 2.5V (i.e., 2.325V). It transitions to high-impedance when V_OUT exceeds this threshold. To generate a logic-high signal, a 100kΩ pullup resistor must connect POK to OUT. During shutdown (SHDN = GND), POK is forcibly held low regardless of output voltage. This behavior allows the MAX1806EUA25+T to provide unambiguous power-good status for microcontroller reset assertion or system-level fault indication.

What thermal considerations apply to the MAX1806EUA25+T in continuous 500mA operation?

In continuous 500mA operation, the MAX1806EUA25+T dissipates up to 1.3W (at VIN = 5.5V, VOUT = 2.5V). Its Power-μMAX package relies on the exposed thermal pad soldered to a PCB ground plane for heat transfer. Without adequate copper area (≥250mm²) and thermal vias, junction temperature can exceed +150°C, triggering thermal shutdown at +170°C. Derating is required above +70°C ambient: power dissipation must decrease by 17mW/°C. For sustained 500mA loads, ensure θ_JA ≤ 65°C/W through proper layout-otherwise output current must be reduced per Figure 3 in the datasheet.

Is the MAX1806EUA25+T pin-compatible with other variants in the MAX1806 family?

Yes, all MAX1806 variants-including MAX1806EUA08+, MAX1806EUA15+, MAX1806EUA18+, MAX1806EUA25+T, and MAX1806EUA33+-share identical 8-pin Power-μMAX pinouts, electrical interfaces, and thermal characteristics. The only difference is the factory-trimmed output voltage (0.8V, 1.5V, 1.8V, 2.5V, or 3.3V), encoded in the part number suffix. This allows direct substitution in existing designs when changing output voltage requirements, provided input voltage margins and load current needs remain compatible with the new variant's specifications.