Analog Devices Inc./Maxim Integrated MAX6390XS31D4

Overview

The MAX6390XS31D4 from Maxim Integrated is a low-power microprocessor supervisory circuit with open-drain active-low reset output, factory-set 3.08V ±2.5% reset threshold, 1120ms VCC reset timeout, and 140ms manual reset timeout. It operates from +1.0V to +5.5V supply, consumes only 3µA at +1.8V, and guarantees valid reset state down to VCC = 1V. Used in battery-powered IoT sensors for reliable brownout detection and manual recovery.

For engineers reviewing the MAX6390XS31D4 datasheet, MAX6390XS31D4 pinout, MAX6390XS31D4 application, or MAX6390XS31D4 equivalent, key selection considerations include its dual-timing reset architecture (1120ms/140ms), SC70-4 open-drain output requiring external pull-up, ±2.5% threshold accuracy over -40°C to +125°C, and compatibility with 1.8V–5.0V logic domains in space-constrained embedded systems.

Technical Context

The MAX6390XS31D4 implements a precision voltage comparator with internal 1.27V reference for RESET IN monitoring and uses a temperature-compensated bandgap reference for VCC threshold detection. Its reset assertion logic combines asynchronous VCC under-voltage detection with synchronous manual reset input debouncing via internal timing control.

Unlike earlier family members, the MAX6390XS31D4 features a dedicated low-value internal MR pullup resistor (1.56kΩ) enabling fast manual reset release and reduced noise susceptibility. Its open-drain RESET output supports wired-OR configurations and level-shifting across mixed-voltage systems without contention.

Key Specifications

Pinout & Package

MAX6390XS31D4 is housed in a lead-free 4-pin SC70 package (X4-1 code), measuring 1.5mm × 1.0mm × 0.8mm, suitable for high-density PCB layouts.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX6326XR31D4 and TPS3808G33DBVR, the MAX6390XS31D4 uniquely balances ultra-small SC70-4 packaging, dual-timing reset control, and aggressive MR pullup strength-making it optimal for compact, manually serviceable, battery-sensitive designs where precise 3.08V trip point is required.

Availability

MAX6390XS31D4 is available at Aetrix Electronics and suitable for industrial PLC modules, battery-powered environmental sensors, automotive body control units, and medical wearable data loggers requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for MAX6390XS31D4 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 and mixed-signal ICs for power, sensing, and interface applications in industrial, automotive, and communications markets.

The MAX6390XS31D4 belongs to the MAX6381–MAX6390 family of low-power µP supervisory circuits engineered specifically for reliable reset generation in space-constrained, wide-temperature, and ultra-low-power embedded systems.

FAQ

What is the exact reset threshold voltage of the MAX6390XS31D4?

The MAX6390XS31D4 has a factory-set reset threshold of 3.08V, with guaranteed accuracy of ±2.5% over the full operating temperature range (-40°C to +125°C). This value corresponds to the "31" suffix in the part number and is optimized for monitoring nominal 3.3V power rails while allowing for typical tolerance drift.

Does the MAX6390XS31D4 require an external pull-up resistor on the RESET pin?

Yes, the MAX6390XS31D4 features an open-drain active-low RESET output, which requires an external pull-up resistor to the target logic voltage (e.g., 1.8V, 3.3V, or 5V). The value is typically 10kΩ–100kΩ; lower values improve rise time but increase static current, while higher values reduce current but risk noise susceptibility.

What are the timing differences between VCC reset and manual reset on the MAX6390XS31D4?

The MAX6390XS31D4 provides asymmetric timing: VCC reset timeout is 1120ms minimum, while manual reset (MR) timeout is 140ms minimum. This design ensures robust power-up sequencing while enabling rapid user-initiated recovery-critical for field-serviceable equipment where operators must trigger resets without waiting for full boot cycles.

Can the MAX6390XS31D4 operate reliably at VCC = 1.0V?

Yes, the MAX6390XS31D4 guarantees correct RESET output logic state down to VCC = 1.0V, as confirmed in the Electrical Characteristics table. This allows deterministic reset assertion during deep brownout events, ensuring the microcontroller remains held in reset until power fully collapses-preventing erratic behavior or flash corruption.

What is the internal pull-up resistance on the MR pin of the MAX6390XS31D4?

The MR pin of the MAX6390XS31D4 has an internal pull-up resistor of 1.56kΩ to VCC, significantly lower than the 63kΩ found in earlier MAX6384–MAX6386 variants. This stronger pull-up reduces susceptibility to noise and enables faster release from manual reset, supporting reliable operation in electrically noisy industrial environments.