Analog Devices Inc./Maxim Integrated MAX6349WHUT+

Overview

The MAX6349WHUT+ from Maxim Integrated is a 150mA low-dropout linear voltage regulator with integrated microprocessor reset circuit, preset to +1.8V output and -10% reset threshold (W variant), housed in SOT23-6 package. It delivers 25µA quiescent current, 180mV dropout at 100mA, and features manual reset input (MR), open-drain active-low RESET output, and reverse leakage protection - designed for battery-powered portable electronics requiring reliable power sequencing and brownout detection.

For engineers reviewing the MAX6349WHUT+ datasheet, MAX6349WHUT+ pinout, MAX6349WHUT+ application, or MAX6349WHUT+ equivalent, this page provides verified technical context, exact pin functions, real-world use cases in handheld instruments and USB devices, and validated alternative parts with documented functional differences.

Technical Context

The MAX6349WHUT+ integrates a P-channel MOSFET LDO regulator core with a precision 1.23V internal reference shared by both regulation and reset functions. Its reset supervisor monitors VOUT continuously and asserts RESET when output falls below 90% of nominal (1.62V for 1.8V output), holding assertion for ≥100ms after recovery.

It implements manual reset via MR pin - a TTL/CMOS-compatible active-low input with 20kΩ internal pullup to OUT, 1µs minimum pulse width, and 500ns MR-to-RESET delay. Unlike the MAX6329, it lacks shutdown but adds deterministic reset initiation independent of supply fault conditions.

Key Specifications

Pinout & Package

MAX6349WHUT+ uses a 6-pin SOT23-6 package with exposed pad (not electrically connected). GND serves dual role as circuit ground and thermal path; soldering to large copper area improves thermal dissipation by up to 30%.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar LDO-with-reset applications.

Compared with MAX6329WHUT+, the MAX6349WHUT+ trades shutdown capability for deterministic manual reset initiation - critical for field service and production test. Versus TPS3808G18DBVR, it integrates regulation and supervision in one die, reducing footprint by 40% and eliminating inter-IC timing skew.

Availability

MAX6349WHUT+ is available at Aetrix Electronics and suitable for hand-held instruments, USB devices, PCMCIA cards, and cordless telephones requiring stable component supply, long-term lifecycle support, and guaranteed traceable sourcing.

Supply support for MAX6349WHUT+ 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, automotive, and communications applications.

The MAX6329/MAX6349 product line targets battery-powered portable equipment needing micropower regulation with integrated supervisory functions - specifically addressing the need for compact, single-chip power sequencing in space-constrained handheld and peripheral designs.

FAQ

What is the function of the SET pin on the MAX6349WHUT+?

The SET pin on the MAX6349WHUT+ serves as the feedback reference node. When connected directly to GND, it configures the device for its preset +1.8V output. It must not be left floating - incorrect connection disables regulation. The internal 1.23V reference connects to SET, enabling adjustable output via external resistor divider if required, though MAX6349WHUT+ is factory-configured for fixed 1.8V operation.

Does the MAX6349WHUT+ require an external pullup resistor on the RESET pin?

Yes, the MAX6349WHUT+ features an open-drain active-low RESET output, which requires an external pullup resistor to VOUT or another appropriate rail to establish a valid logic-high level. Typical values range from 10kΩ to 100kΩ. Without this pullup, RESET cannot transition high, preventing proper microprocessor release after power stabilization or manual reset release.

Can the MAX6349WHUT+ operate with input voltage below 2.5V?

No, the MAX6349WHUT+ has a specified input voltage range of +2.5V to +5.5V per Absolute Maximum Ratings and Electrical Characteristics tables. Operation below 2.5V violates datasheet limits and may result in unregulated output, undefined reset behavior, or failure to maintain 1.8V output - especially near dropout where VIN < VOUT + 180mV (i.e., <1.98V) causes regulation loss.

How does the MR pin behave during normal operation of the MAX6349WHUT+?

During normal operation, the MR pin on the MAX6349WHUT+ remains inactive (high) due to its internal 20kΩ pullup to OUT. It draws negligible current (<100nA) and has no effect on regulation or reset state unless actively driven low. If unused, MR may be left unconnected or tied to OUT; no external pullup is required beyond the internal one.

What thermal considerations apply to the MAX6349WHUT+ in continuous 150mA operation?

In continuous 150mA operation at VIN = 5.5V, the MAX6349WHUT+ dissipates ~555mW (P = IOUT × (VIN − VOUT)). With θJA = 140°C/W and TA = +85°C, junction temperature reaches ~163°C - exceeding the 150°C absolute maximum. To sustain 150mA, reduce VIN, improve PCB copper area under GND, or limit duty cycle. Derating to 100mA at 5.5V keeps TJ ≈ 135°C with standard layout.