Analog Devices Inc./Maxim Integrated MAX691EPE+

Overview

MAX691EPE+ from Maxim Integrated is a 16-pin microprocessor supervisory circuit providing reset generation, battery backup switchover, watchdog timer, power-fail detection, and CE gating for CMOS RAM. It features 4.65V reset threshold, 200ms reset timeout, 1.6s/100ms selectable watchdog, 1.3V PFI comparator, and VOUT switching between VCC and VBATT. Used in industrial controllers and automotive ECUs requiring reliable µP power monitoring and data retention during brownouts.

For engineers reviewing the MAX691EPE+ datasheet, MAX691EPE+ pinout, MAX691EPE+ application, or MAX691EPE+ equivalent, key selection considerations include its E-suffix industrial temperature range (–40°C to +85°C), 16-pin PDIP package, integrated CE OUT write protection logic, adjustable timing via OSC SEL/OSC IN, and compatibility with 2.0V–4.25V backup batteries.

Technical Context

The MAX691EPE+ integrates five core supervisory functions in a single IC: precision voltage monitoring with 4.65V ±150mV reset threshold and 40mV hysteresis; dual-mode watchdog timer (internal oscillator or external clock input) with 100ms/1.6s timeout selection; battery switchover using internal PNP and MOSFET paths with 50mV/70mV power-down/power-up thresholds; 1.3V reference-based power-fail comparator with PFO output; and CE IN/CE OUT gating that forces CE OUT high when VCC drops below 4.65V to prevent RAM corruption.

Its architecture includes a dedicated timebase oscillator, transition detector on WDI, monostable for RESET pulse generation, and independent logic blocks for LOW LINE, BATT ON, and WDO outputs. All timing parameters are configurable via OSC SEL and OSC IN pins, enabling system-specific tuning of reset delay and watchdog timeout without external components.

Key Specifications

Pinout & Package

MAX691EPE+ is supplied in a 16-pin plastic DIP (PDIP) package with 0.3-inch width, through-hole mounting, and industry-standard pin spacing. Pin 1 is marked with a notch or dot; pin numbering follows standard counter-clockwise convention from top-left corner.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX691CPD+, MAX691EPE+ adds –40°C start-up capability and guaranteed operation up to +85°C, critical for outdoor or engine-bay deployments; versus MAX695EPE+, it provides higher reset threshold margin for legacy 5V rails with minimal regulation headroom.

Availability

MAX691EPE+ is available at Aetrix Electronics and suitable for industrial controllers, automotive ECUs, medical instrumentation, and smart energy meters requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for MAX691EPE+ 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 computing applications.

The MAX690–MAX695 family was designed to replace discrete reset, battery switchover, and watchdog circuits in µP-based systems-reducing board space, improving reliability, and simplifying design validation for mission-critical power monitoring.

FAQ

What is the operating temperature range of the MAX691EPE+?

The MAX691EPE+ is rated for –40°C to +85°C (E-suffix), making it suitable for industrial and automotive environments where ambient temperatures exceed commercial-grade limits. This range is validated per Maxim's production test flow and includes full electrical characterization at both extremes. The MAX691EPE+ maintains specified reset threshold accuracy, watchdog timing, and battery switchover behavior across this span without derating.

Does the MAX691EPE+ support adjustable reset timeout periods?

No-the MAX691EPE+ has a fixed 200ms reset timeout period, as defined in the MAX694/MAX695 variant group. Unlike the MAX691's sibling MAX695 (which offers selectable reset delays), the MAX691EPE+ uses a hardwired monostable circuit tied to its internal oscillator. This simplifies layout and eliminates timing uncertainty but requires system-level verification that 200ms meets µP initialization requirements.

How does the CE OUT pin protect CMOS RAM during power failure?

The MAX691EPE+ forces CE OUT high whenever VCC drops below 4.65V (or VBATT exceeds VCC), regardless of CE IN state. This overrides the microprocessor's chip-select signal and places CMOS RAM in high-impedance mode, preventing spurious writes during brownout. The action occurs within 50ns propagation delay, faster than most µP bus cycles, ensuring data integrity even during rapid voltage collapse.

Can the MAX691EPE+ be used with a 3.3V microprocessor system?

The MAX691EPE+ is designed for 5V systems: its reset threshold (4.65V), VCC operating range (4.75V–5.5V), and VOUT switching logic assume a nominal 5V rail. Using it with a 3.3V µP risks improper reset assertion and undefined CE OUT behavior. For 3.3V systems, consider the MAX6361 or MAX6363 families, which feature 3.08V/3.3V reset thresholds and compatible timing.

What is the maximum load current supported by VOUT in battery backup mode?

In battery backup mode (VCC = 0V), the MAX691EPE+ delivers up to 250µA from VBATT through VOUT with a typical dropout of 20mV. This is sufficient for static CMOS RAM and real-time clocks drawing <100µA. Exceeding 250µA risks VOUT droop below required logic levels; for higher loads, use the BATT ON output to drive an external PNP transistor and route VBATT directly to the load.