Analog Devices Inc./Maxim Integrated MAX691ACWE+T

Overview

The MAX691ACWE+T from Maxim Integrated is a microprocessor supervisory circuit designed for critical 5V power monitoring and system reset control in embedded systems. It provides dual active-low/high RESET outputs, battery switchover (VBATT to VOUT), chip-enable gating, watchdog timer, and power-fail detection - with 4.65V reset threshold, 200ms reset timeout, 30μA operating current, and guaranteed RESET assertion down to VCC = 1V. It is used in industrial controllers and intelligent instruments requiring reliable brownout protection.

For engineers reviewing the MAX691ACWE+T datasheet, MAX691ACWE+T pinout, MAX691ACWE+T application, or MAX691ACWE+T equivalent, this page delivers verified technical context, package-specific pin functions, real-world design meanings of key specs, and two validated alternative parts for power-monitoring supervisory circuits.

Technical Context

The MAX691ACWE+T integrates a precision voltage monitor (4.65V ±15mV hysteresis), internal oscillator (100kHz typical with 47pF capacitor), and dual-mode watchdog (1.6s nominal / 100ms short period). Its VCC-to-VOUT PMOS switch (0.8–1.2Ω) and VBATT-to-VOUT diode path (15–30Ω) enable seamless backup power handoff when VCC drops below VBATT − 0.3V.

It features open-drain RESET and RESET outputs, a buffered LOW LINE comparator output, and CE IN/CE OUT transmission gate (6–10ns propagation delay, 75–150Ω on-resistance) that disables during reset to prevent RAM corruption. The WDI input uses internal voltage-divider biasing (1.6V typ) to disable watchdog when floating.

Key Specifications

Pinout & Package

MAX691ACWE+T is supplied in a 16-pin Wide SO (SOIC-W) package, 7.5mm body width, 1.27mm pitch, RoHS-compliant lead-free finish (+T suffix).

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX691AEWE+T, the MAX691ACWE+T offers cost-optimized commercial-temperature operation; compared with MAX693ACWE+T, it provides higher reset threshold margin for noisy 5V rails - both alternatives require validation of reset timing and voltage thresholds in the target application.

Availability

MAX691ACWE+T is available at Aetrix Electronics and suitable for industrial controllers, intelligent instruments, and critical μP power monitoring applications requiring stable component supply, long-term lifecycle support, and traceable sourcing.

Supply support for MAX691ACWE+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) is a semiconductor company specializing in high-performance analog, mixed-signal, and power management ICs for industrial, computing, and communications markets.

The MAX691A family was designed specifically for robust microprocessor supervision in noise-prone 5V systems - integrating reset generation, battery switchover, watchdog, and memory protection in a single 16-pin package.

FAQ

What is the reset threshold voltage of the MAX691ACWE+T?

The MAX691ACWE+T has a typical reset threshold voltage of 4.65V, with a guaranteed range of 4.50V to 4.75V over temperature and supply. This value is specific to the MAX691A variant and differs from the 4.40V threshold of the MAX693A series. The MAX691ACWE+T maintains 15mV hysteresis to prevent chatter near the trip point, ensuring clean reset assertion and deassertion.

Does the MAX691ACWE+T support battery backup operation?

Yes, the MAX691ACWE+T fully supports battery backup operation. When VCC falls below VBATT − 0.3V and below the 4.65V reset threshold, it automatically switches VOUT sourcing from VCC to VBATT. In this mode, the MAX691ACWE+T draws only 0.04–1µA from the battery (depending on temperature), and guarantees RESET assertion remains valid - enabling long-term data retention in CMOS RAM or EEPROM.

Can the MAX691ACWE+T watchdog timer be disabled?

Yes, the watchdog timer in the MAX691ACWE+T is disabled by leaving the WDI pin unconnected. An internal voltage divider biases WDI to ~1.6V, which the internal comparators recognize as an invalid level, thereby disabling watchdog functionality. No external pullup or pulldown is required - this is a built-in feature confirmed in the MAX691ACWE+T datasheet's "Watchdog Input" section.

What is the purpose of the CE IN and CE OUT pins on the MAX691ACWE+T?

The CE IN and CE OUT pins on the MAX691ACWE+T implement hardware-enforced chip-enable gating. During normal operation, CE IN passes directly to CE OUT with <10ns delay. When RESET is asserted (e.g., during power-down), the path is disabled - preventing spurious writes to external CMOS RAM or EEPROM. This function is integral to the MAX691ACWE+T's role as a supervisory IC for memory-critical systems.

Is the MAX691ACWE+T pin-compatible with older MAX691 versions?

Yes, the MAX691ACWE+T is a pin-compatible upgrade to the original MAX691. It retains identical pinout, package (16-pin Wide SO), and core functionality while improving key specs: reduced supply current (30μA vs. older 100μA), tighter reset threshold accuracy, and enhanced CE propagation delay (6–10ns vs. older 15ns). No PCB changes are needed when upgrading from MAX691CWE to MAX691ACWE+T.