Analog Devices Inc./Maxim Integrated MAX6389XS31D3+T

Overview

MAX6389XS31D3+T from Maxim Integrated is a low-power, open-drain active-low microprocessor supervisory circuit with factory-set 3.08V reset threshold, 140ms minimum VCC reset timeout, and auxiliary RESET IN input for dual-voltage monitoring. It operates from +1.0V to +5.5V supply, consumes only 3μA at +1.8V, and guarantees valid reset output down to VCC = 1V. Used in battery-powered instrumentation and dual-rail embedded systems requiring precise brownout detection.

For engineers reviewing the MAX6389XS31D3+T datasheet, MAX6389XS31D3+T pinout, MAX6389XS31D3+T application, or MAX6389XS31D3+T equivalent, key selection criteria include its 3.08V ±2.5% threshold accuracy over –40°C to +125°C, 140ms reset timeout, open-drain output requiring external pullup, and dedicated RESET IN comparator referenced to +1.27V for secondary voltage supervision.

Technical Context

The MAX6389XS31D3+T integrates a precision bandgap reference and comparator to monitor VCC against a fixed 3.08V threshold, asserting open-drain RESET when VCC falls below that level. Its internal timer enforces a guaranteed minimum 140ms reset assertion after VCC recovers above threshold.

A separate high-impedance RESET IN input compares external voltage to an internal +1.27V reference; reset triggers if either VCC < 3.08V or RESET IN < 1.27V. This dual-comparator architecture enables independent monitoring of core and I/O rails without external components.

Key Specifications

Pinout & Package

MAX6389XS31D3+T is housed in a RoHS-compliant 4-pin SC70 package (outline 21-0098), measuring 2.0mm × 2.1mm × 0.95mm, suitable for space-constrained PCB layouts in portable and automotive modules.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX6389XS31D3+T, the LT31D3 variant offers identical functionality in a thermally robust µDFN package, while TPS3808G33DBVR simplifies design for single-supply applications but sacrifices dual-rail capability and open-drain configurability.

Availability

MAX6389XS31D3+T is available at Aetrix Electronics and suitable for portable instrumentation, automotive body electronics, industrial PLC I/O modules, and battery-powered sensor nodes requiring stable component supply and long-term lifecycle support.

Supply support for MAX6389XS31D3+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, automotive, and computing applications.

The MAX6381–MAX6390 family delivers ultra-low-power, high-accuracy reset supervision for microprocessor-based systems operating across extended temperature ranges and multiple voltage domains.

FAQ

What is the exact reset threshold voltage of MAX6389XS31D3+T and how is it specified over temperature?

The MAX6389XS31D3+T has a factory-set nominal reset threshold of 3.08V, with tolerance of ±2.5% over the full operating temperature range of –40°C to +125°C. This specification is guaranteed by design and applies to both VCC monitoring and the internal reference used for RESET IN comparison. The threshold remains stable with a tempco of 60ppm/°C, ensuring predictable behavior across thermal extremes in automotive and industrial deployments.

Does MAX6389XS31D3+T require an external pullup resistor on the RESET pin, and what value is recommended?

Yes, MAX6389XS31D3+T features an open-drain active-low RESET output and requires an external pullup resistor. A 10kΩ to 100kΩ resistor to the target logic rail (e.g., 3.3V or 5V) is typical. The device can sink up to 3.2mA at VCC ≥ 4.5V, so the pullup must be sized to ensure VOL ≤ 0.4V under worst-case load. For most applications, 47kΩ provides optimal noise immunity and power efficiency without compromising rise time.

How does the RESET IN function work on MAX6389XS31D3+T, and what is its reference voltage?

The RESET IN input on MAX6389XS31D3+T compares the applied voltage to an internal +1.27V reference. When the voltage at RESET IN falls below this threshold, the device asserts RESET regardless of VCC status. To monitor a secondary supply (e.g., 2.5V), connect a resistor divider between that rail and GND, with the midpoint fed to RESET IN. The MAX6389XS31D3+T's ±1nA input leakage enables accurate scaling using high-value resistors without loading error.

What is the minimum supply voltage at which MAX6389XS31D3+T guarantees correct RESET output logic state?

MAX6389XS31D3+T guarantees valid RESET output logic state down to VCC = 1.0V. Below this, the internal comparators and timer may not operate reliably. This feature ensures deterministic reset behavior during deep brownout events - for example, allowing a microcontroller to execute last-chance data save routines before complete power collapse. The open-drain output remains functional (though sinking capability degrades) as VCC approaches 1V.

Is MAX6389XS31D3+T qualified for automotive applications, and what packaging indicates this qualification?

No, MAX6389XS31D3+T is not automotive-qualified. Its ordering suffix "+T" denotes RoHS-compliant packaging only. Automotive-grade versions carry the "/V" suffix (e.g., MAX6389XS31D3/V+T) and undergo AEC-Q100 stress testing. The MAX6389XS31D3+T is rated for –40°C to +125°C operation but lacks the additional screening, traceability, and failure-rate validation required for automotive safety-critical systems.