Analog Devices Inc./Maxim Integrated MAX691EWE/R70033

Overview

MAX691EWE/R70033 from Maxim Integrated is a microprocessor supervisory circuit designed for power supply monitoring and reset generation in embedded systems. It provides precision voltage threshold detection (4.65V ±1.5%), watchdog timer, manual reset input, and power-fail comparator - all in a 16-pin SOIC package. It ensures reliable system startup and brownout recovery in industrial controllers and battery-backed memory systems.

For engineers reviewing the MAX691EWE/R70033 datasheet, MAX691EWE/R70033 pinout, MAX691EWE/R70033 application, or MAX691EWE/R70033 equivalent, key selection considerations include its fixed 4.65V reset threshold, 1.6s watchdog timeout, active-low reset output with push-pull drive, power-fail detection capability, and compatibility with 5V logic systems requiring guaranteed reset assertion during power ramp-up and dropout.

Technical Context

The MAX691EWE/R70033 integrates four core functions: a precision bandgap reference-based voltage monitor, a programmable watchdog timer with 1.6s timeout, a manual reset input (MR), and a power-fail comparator (PFI/PFO). Its reset output (RESET) is asserted low when V_CC falls below 4.65V and remains valid down to V_CC = 1.0V.

The watchdog timer requires periodic toggling of the WD input to prevent timeout; failure triggers RESET assertion. The PFI input monitors an external voltage (e.g., backup battery or auxiliary rail), and asserts PFO low when that voltage drops below 1.25V - independent of V_CC status. All logic inputs are TTL/CMOS compatible.

Key Specifications

Pinout & Package

MAX691EWE/R70033 is housed in a 16-pin SOIC (Small Outline Integrated Circuit) package with 1.27mm pitch, JEDEC MS-012AC compliant, body width 3.9mm, and RoHS-compliant lead-free finish.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX692EWE+, the MAX691EWE/R70033 offers tighter system startup timing due to its lower 4.65V threshold; compared with TPS3823-46DBVR, it delivers full system supervision (watchdog + PFI) in a single 16-pin SOIC, avoiding design compromises in safety-critical 5V embedded platforms.

Availability

MAX691EWE/R70033 is available at Aetrix Electronics and suitable for industrial automation, medical device manufacturing, and smart metering applications requiring stable component supply, long-lifecycle support, and guaranteed reset reliability under voltage transients.

Supply support for MAX691EWE/R70033 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, automotive, and communications markets.

The MAX691EWE/R70033 belongs to Maxim's microprocessor supervisory product line, engineered specifically for robust power monitoring and fail-safe reset generation in mission-critical 5V embedded systems where deterministic behavior under brownout and watchdog fault conditions is mandatory.

FAQ

What is the exact reset threshold voltage of the MAX691EWE/R70033?

The MAX691EWE/R70033 has a precision reset threshold of 4.65V with ±1.5% tolerance over temperature (-40°C to +85°C). This value is laser-trimmed at wafer test and guaranteed in the datasheet's DC characteristics table. The MAX691EWE/R70033 asserts its active-low RESET output whenever V_CC falls below this threshold and maintains assertion until V_CC rises 100mV above it and remains stable for ≥200ms.

Does the MAX691EWE/R70033 require external components to operate?

The MAX691EWE/R70033 requires only a 0.1µF ceramic bypass capacitor between V_CC and GND, placed adjacent to pins 1 and 16. No external resistors, capacitors, or timing components are needed for basic reset, watchdog, or power-fail functions. The MAX691EWE/R70033 integrates all reference, comparator, and timer circuitry internally, making it a true plug-and-play supervisory solution.

Can the MAX691EWE/R70033 monitor a 3.3V auxiliary rail?

Yes - the MAX691EWE/R70033 can monitor any external voltage using its PFI (Power-Fail Input) pin. When the voltage applied to PFI drops below 1.25V, the device asserts its open-drain PFO output low. To monitor a 3.3V rail, use a resistor divider (e.g., 1.0MΩ + 604kΩ) to scale 3.3V down to 1.25V at PFI. The MAX691EWE/R70033's PFI input draws only 10nA, minimizing divider current error.

Is the MAX691EWE/R70033 pin-compatible with other Maxim supervisory ICs?

The MAX691EWE/R70033 shares the same 16-pin SOIC footprint and pin assignments with the MAX692EWE+ (4.75V threshold) and MAX693EWE+ (4.40V threshold), enabling drop-in replacement within the same family. However, it is not pin-compatible with 8-pin or 5-pin supervisors like the MAX809 or TPS3823. Always verify V_CC range, reset threshold, and feature set before substitution - the MAX691EWE/R70033 specifically requires 4.75V–5.5V operation.

What is the watchdog timeout period of the MAX691EWE/R70033?

The MAX691EWE/R70033 features a fixed 1.6-second watchdog timeout period. The WD input must be toggled (high-to-low or low-to-high) at least once every 1.6s to prevent timeout. If no transition occurs within that window, the device asserts RESET low. This timeout is factory-trimmed and guaranteed across temperature and supply voltage - no external components affect its value. The MAX691EWE/R70033 uses this to provide hardware-enforced firmware liveness checking.