Analog Devices Inc./Maxim Integrated MAX6389XS46D1

Overview

MAX6389XS46D1 from Maxim Integrated is a single-supply, open-drain active-low microprocessor supervisory circuit with factory-set 4.63V reset threshold, 140ms minimum reset timeout, and auxiliary RESET IN input for dual-voltage monitoring. It operates from +1.0V to +5.5V, consumes only 3µA at +1.8V, and guarantees valid reset output down to VCC = 1V. It is used in portable battery-powered equipment requiring precise brownout detection and secondary supply monitoring.

For engineers reviewing the MAX6389XS46D1 datasheet, MAX6389XS46D1 pinout, MAX6389XS46D1 application, or MAX6389XS46D1 equivalent, key selection criteria include its 4.63V ±2.5% threshold accuracy over –40°C to +125°C, 140ms VCC reset timeout, open-drain output requiring external pull-up, auxiliary RESET IN comparator referenced to +1.27V, and SC70-4 package compatibility with space-constrained embedded systems.

Technical Context

The MAX6389XS46D1 integrates a precision bandgap reference and comparator to monitor VCC against a fixed 4.63V threshold, asserting reset when voltage falls below this level. Its internal timer ensures reset remains active for ≥140ms after VCC recovers above threshold.

A dedicated auxiliary RESET IN input compares external voltage to an internal +1.27V reference, enabling independent monitoring of a second supply rail via resistor divider. The open-drain RESET output requires an external pull-up resistor and sinks up to 3.2mA at VCC ≥ 4.5V while maintaining VOL ≤ 0.4V.

Key Specifications

Pinout & Package

MAX6389XS46D1 is housed in a lead-free 4-pin SC70 package (pkg code X4-1), measuring 1.3mm × 1.1mm × 0.6mm with 0.65mm pitch. Pin 1 is marked by a dot; pin 1 = VCC, pin 2 = RESET, pin 3 = RESET IN, pin 4 = GND.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX6389LT46D1, the MAX6389XS46D1 offers identical supervision functionality in a smaller SC70-4 package but with higher thermal resistance; compared with TPS3808G33DBVR, it provides dual-rail capability and tighter threshold accuracy at the cost of open-drain interface complexity.

Availability

MAX6389XS46D1 is available at Aetrix Electronics and suitable for battery-powered IoT sensors, automotive body control modules, and industrial PLC I/O cards requiring stable component supply and guaranteed long-term availability.

Supply support for MAX6389XS46D1 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 industrial, automotive, and communications applications, with expertise in low-power supervision and power management.

The MAX6381–MAX6390 family was developed specifically for space-constrained, low-power microprocessor supervision in dual-voltage systems, emphasizing accuracy, ultra-low quiescent current, and auxiliary rail monitoring capability.

FAQ

What is the exact reset threshold voltage of MAX6389XS46D1 and how stable is it over temperature?

The MAX6389XS46D1 has a factory-set nominal reset threshold of 4.63V, with guaranteed accuracy of ±2.5% over the full industrial temperature range of –40°C to +125°C. This stability is achieved through laser-trimmed resistors and a precision bandgap reference, making MAX6389XS46D1 suitable for applications where supply tolerance margins are tight, such as 5V systems with ±5% regulation.

Does MAX6389XS46D1 support monitoring of a second voltage rail, and how is it configured?

Yes, MAX6389XS46D1 supports dual-voltage supervision via its RESET IN pin, which connects to an internal +1.27V reference comparator. To monitor a second rail (e.g., 3.3V), connect a resistor divider between that rail and GND, with the midpoint fed to RESET IN. For example, a 10kΩ/10kΩ divider on a 3.3V rail yields 1.65V at RESET IN - well above the 1.27V trip point - allowing precise threshold setting per the formula V_INTH = 1.27V × (R1/R2 + 1).

What is the function of the RESET output on MAX6389XS46D1, and what external components are required?

The RESET output of MAX6389XS46D1 is an open-drain active-low signal, meaning it can only sink current when asserted and requires an external pull-up resistor to the host logic rail (e.g., 3.3V or 5V). No pull-down is needed. Typical pull-up values range from 10kΩ to 100kΩ; the device sinks up to 3.2mA at VCC ≥ 4.5V while maintaining VOL ≤ 0.4V, ensuring robust logic-level compatibility in MAX6389XS46D1-based designs.

How does the 140ms reset timeout of MAX6389XS46D1 benefit system reliability?

The 140ms minimum reset timeout of MAX6389XS46D1 ensures the microprocessor remains held in reset long enough for all internal power domains to stabilize, clocks to lock, and memory to initialize reliably after power-up or brownout recovery. This eliminates race conditions and undefined states in timing-critical firmware startup sequences, directly improving field reliability in MAX6389XS46D1-deployed products such as medical diagnostic tools and industrial controllers.

Can MAX6389XS46D1 operate correctly when VCC drops below 1.8V, and what is its lowest functional supply voltage?

Yes, MAX6389XS46D1 is fully specified to operate down to VCC = 1.0V, with guaranteed valid reset output logic state (correct high/low assertion) across this entire range. Its supply current drops to just 3µA at +1.8V and remains functional at 1.0V - enabling graceful shutdown and fail-safe reset assertion during deep brownout events, a key requirement in MAX6389XS46D1 applications like battery-backed real-time clocks and safety-critical edge nodes.