Analog Devices Inc./Maxim Integrated MAX691AEUE

Overview

MAX691AEUE from Maxim Integrated is a microprocessor supervisory circuit providing power-on reset, watchdog timer, battery switchover, and chip-enable gating for 5V systems. It features 4.65V reset threshold, 200ms reset timeout, 30μA operating supply current, and guaranteed RESET assertion down to VCC = 1V. Used in embedded controllers and intelligent instruments requiring reliable brownout protection and nonvolatile memory write protection.

For engineers reviewing the MAX691AEUE datasheet, MAX691AEUE pinout, MAX691AEUE application, or MAX691AEUE equivalent, key selection criteria include reset threshold accuracy (±150mV), battery-backup mode operation with VBATT ≥ 2.0V, CE propagation delay ≤ 10ns, and compatibility with MaxCap®/SuperCap™ backup capacitors.

Technical Context

The MAX691AEUE integrates a precision voltage monitor, internal oscillator-based reset generator, and dual-mode watchdog timer with selectable timeout periods (100ms/1.6s). Its reset logic asserts both active-low RESET and active-high RESET outputs synchronously upon VCC falling below 4.65V, maintaining assertion for 200ms after VCC rises above threshold.

It implements bidirectional power-path control via VCC/VBATT switchover with hysteresis (60mV), supports external timing capacitor or clock input at OSC IN, and provides on-chip CE signal gating with 75Ω series resistance and <10ns propagation delay under 50pF load.

Key Specifications

Pinout & Package

MAX691AEUE is housed in a 16-pin TSSOP package (5.0mm × 4.4mm, 0.65mm pitch) with exposed pad for thermal enhancement. Pin numbering follows standard JEDEC outline MO-153.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX691ACUE and MAX693AESE, the MAX691AEUE offers the widest operational temperature range among 4.65V-threshold variants and guarantees reset validity down to VCC = 1V-critical for systems with aggressive low-voltage operation or long hold-up times.

Availability

MAX691AEUE is available at Aetrix Electronics and suitable for industrial controllers, intelligent instrumentation, critical μP power monitoring, and computing system health management requiring stable component supply across extended temperature ranges.

Supply support for MAX691AEUE 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) is a semiconductor company specializing in high-performance analog, mixed-signal, and power management ICs for industrial, computing, and communications applications.

The MAX691A family was designed specifically for robust microprocessor supervision in mission-critical embedded systems requiring guaranteed reset behavior, battery backup, and integrated watchdog functionality.

FAQ

What is the guaranteed minimum operating voltage for RESET assertion in MAX691AEUE?

The MAX691AEUE guarantees RESET assertion remains valid down to VCC = 1V. This is achieved through specialized internal circuitry that maintains gate drive to the RESET output transistor even at ultra-low supply levels. Below 1V, an external 10kΩ pulldown resistor on the RESET pin ensures saturation voltage stays below 0.4V while sinking 40μA-making MAX691AEUE uniquely suited for deep brownout resilience in safety-critical systems.

How does the MAX691AEUE handle chip-enable (CE) signal gating during power failure?

The MAX691AEUE disables the CE path by turning off the internal 75Ω transmission gate between CE IN and CE OUT whenever RESET is asserted-either due to VCC brownout or watchdog timeout. During this state, CE IN enters high-impedance mode (<±1μA leakage), and CE OUT is actively pulled to VOUT. This prevents spurious memory writes to CMOS RAM or EEPROM during unstable power conditions, eliminating the need for external gating logic in the MAX691AEUE design.

Can the MAX691AEUE be used with supercapacitors larger than 0.47F?

Yes-the MAX691AEUE is explicitly MaxCap® and SuperCap™ compatible, supporting backup capacitors up to at least 1F per datasheet guidance. Its VBATT input handles peak currents up to 250mA during initial charge and continuous discharge up to 25mA. For capacitors >0.47F, ensure the charging circuit limits inrush current to avoid exceeding the 250mA VBATT peak rating, and verify voltage derating (e.g., 2.7V-rated cap for 2.8V VBATT) to maintain reliability.

What is the function of the OSC SEL and OSC IN pins on the MAX691AEUE?

OSC SEL and OSC IN jointly configure the MAX691AEUE's timing engine. When OSC SEL is floating or high, the internal oscillator sets fixed 200ms reset and 1.6s watchdog timeouts. When OSC SEL is low, OSC IN accepts either an external clock signal or a timing capacitor (e.g., 47pF) to adjust timeouts-enabling 1024/4096 clock-cycle or (600/C)ms/(2.4/C)sec programmability. This dual-mode flexibility allows precise tuning without adding external crystals or oscillators.

Does the MAX691AEUE provide separate watchdog and reset outputs?

Yes-the MAX691AEUE provides three distinct reset-related outputs: active-low RESET, active-high RESET (open-drain complement), and dedicated WDO (Watchdog Output). WDO asserts low independently when the watchdog timer expires-regardless of reset state-and remains low until the next WDI transition. This enables system-level fault isolation: WDO can trigger diagnostics or logging, while RESET forces full μP reboot, giving designers granular control over recovery strategies in the MAX691AEUE implementation.