Analog Devices Inc./Maxim Integrated MAX691EWE

Overview

MAX691EWE from Maxim Integrated is a 16-pin microprocessor supervisory circuit providing reset generation, battery backup switchover, adjustable watchdog timer, power-fail detection, and CE gating for CMOS RAM/EEPROM. It features 4.65V reset threshold, 1.6s/100ms selectable watchdog timeout, 200ms reset delay, 1.3V PFI comparator, and VOUT switching between VCC and VBATT (2.0–4.25V). Used in industrial controllers and automotive ECUs for reliable µP power monitoring and data retention during brownouts.

For engineers reviewing the MAX691EWE datasheet, MAX691EWE pinout, MAX691EWE application, or MAX691EWE equivalent, key selection criteria include its E-suffix industrial temperature range (–40°C to +85°C), SOIC-16W package, integrated chip-enable gating with 50ns propagation delay, and dual-mode oscillator (internal/external) enabling precise timing control in safety-critical embedded systems.

Technical Context

The MAX691EWE implements a precision voltage monitor with 4.65V ±150mV reset threshold and 40mV hysteresis, ensuring stable reset assertion during VCC transients. Its battery switchover circuit uses a 200Ω MOSFET to connect VBATT to VOUT when VCC drops below VBATT −70mV (rising) or VBATT −50mV (falling), with 20mV hysteresis to prevent chatter.

Watchdog functionality relies on a dual-mode oscillator: internal (6.55kHz nominal) or external (0–250kHz via OSC IN), allowing configurable timeout periods (100ms or 1.6s) and reset delays (50ms or 200ms). The CE gating logic forces CE OUT high whenever VCC falls below 4.65V, independently of CE IN, preventing erroneous RAM writes during undervoltage conditions.

Key Specifications

Pinout & Package

MAX691EWE is housed in a 16-pin wide-body SOIC (SOIC-16W) package, 7.5mm body width, 1.27mm pitch, RoHS-compliant, rated for –40°C to +85°C operation.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX691CWE and MAX695EWE, the MAX691EWE uniquely combines industrial temperature range, 4.65V reset threshold for tight 5V ±5% compliance, and 4.25V max VBATT support-making it the only option qualified for automotive-grade brownout resilience and high-VBATT coin-cell backup.

Availability

MAX691EWE is available at Aetrix Electronics and suitable for industrial PLC controllers, automotive body control modules, medical infusion pumps, and smart energy meters requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for MAX691EWE 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 computing applications, with emphasis on reliability, integration, and low-power operation.

The MAX690–MAX695 family was engineered specifically for µP-based systems needing consolidated power monitoring, battery backup, and data integrity protection-replacing discrete reset ICs, watchdog timers, and RAM write-protection logic in space-constrained embedded designs.

FAQ

What is the operating temperature range of the MAX691EWE?

The MAX691EWE is specified for operation from –40°C to +85°C, denoted by its "E" suffix. This industrial temperature grade ensures reliable performance in automotive under-hood environments, factory automation equipment, and outdoor metering systems where ambient extremes are common. The device maintains full electrical specifications-including 4.65V reset threshold accuracy and 1µA backup current-across this entire range, as validated in Maxim's production testing.

How does the MAX691EWE handle battery switchover during VCC brownout?

The MAX691EWE uses an internal comparator with 70mV rising-edge and 50mV falling-edge thresholds to switch VOUT between VCC and VBATT. When VCC drops below VBATT −50mV, the 200Ω MOSFET connects VBATT to VOUT within microseconds. Hysteresis prevents oscillation during slow decay. VOUT remains stable at VBATT −0.02V (typ.) under 250µA load, preserving RAM/RTC operation without external components.

Can the MAX691EWE replace the MAX690 or MAX692 in an existing design?

No-MAX691EWE is not a drop-in replacement for the 8-pin MAX690/MAX692 due to different pin count (16 vs. 8), package (SOIC-16W vs. SOIC-8), and feature set (includes CE gating, BATT ON, WDO, OSC SEL/IN). While both families share core supervision functions, the MAX691EWE requires PCB layout revision and firmware updates to leverage its adjustable timing and enhanced protection features.

What is the purpose of the CE IN and CE OUT pins on the MAX691EWE?

CE IN and CE OUT implement hardware write protection for CMOS RAM or EEPROM. When VCC ≥ 4.65V, CE OUT mirrors CE IN with 50ns delay. If VCC drops below 4.65V, CE OUT is forced high-regardless of CE IN state-blocking write access to memory. This prevents corruption during power-up, brownout, or reset, eliminating need for software-based write locks or external logic gates in the MAX691EWE design.

Does the MAX691EWE support external clock input for the watchdog timer?

Yes-the MAX691EWE supports external clock input via the OSC IN pin when OSC SEL is held low. In this mode, the watchdog timeout period is determined by clock cycles (e.g., 1024 cycles for short timeout, 4096 for long), enabling precise, system-synchronized supervision independent of internal oscillator drift. External clock frequency range is 0–250kHz, allowing synchronization to main µP clock or dedicated timing source.