Analog Devices Inc./Maxim Integrated MAX691AEJE

Overview

The MAX691AEJE 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/EEPROM. It features a 4.65V reset threshold, 50ms/200ms selectable reset timeout, 1.6s/100ms watchdog timeout, 1.3V PFI comparator, and VOUT switching between VCC and VBATT. It is used in industrial controllers and intelligent instruments requiring reliable power monitoring and data retention during brownouts.

For engineers reviewing the MAX691AEJE datasheet, MAX691AEJE pinout, MAX691AEJE application, or MAX691AEJE equivalent, key selection criteria include its 16-pin SOIC package, E-suffix –40°C to +85°C operating range, battery switchover hysteresis (20mV), CE OUT propagation delay (50–200ns), and compatibility with 2.0–4.25V backup batteries.

Technical Context

The MAX691AEJE integrates five core supervisory functions in a single IC: precision reset generation with 4.65V threshold and 40mV hysteresis; dual-mode watchdog timer (internal oscillator or external clock input via OSC IN/OSC SEL); bidirectional battery switchover with 70mV turn-on and 50mV turn-off thresholds; 1.3V reference-based power-fail detection with PFO output; and active-high CE OUT with gated logic that forces high when VCC drops below reset threshold.

Its architecture includes an internal 6.55kHz oscillator, three-level WDI input with mid-supply bias (38% VCC), BATT ON output capable of sinking 25mA, and LOW LINE output that tracks VCC relative to reset threshold without delay. All timing parameters-including reset timeout and watchdog period-are configurable via OSC SEL and OSC IN pins per Table 1 in the datasheet.

Key Specifications

Pinout & Package

MAX691AEJE is housed in a 16-pin SOIC (Small Outline Integrated Circuit) package with 1.27mm pitch, JEDEC MS-012AC compliant, rated for –40°C to +85°C operation (E suffix).

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX691CSA+ and TPS3823MPW, the MAX691AEJE uniquely combines full battery switchover control, CE gating, and configurable watchdog in a single 16-pin SOIC-enabling complete µP supervision without supplemental ICs or discrete logic.

Availability

MAX691AEJE is available at Aetrix Electronics and suitable for industrial controllers, intelligent instruments, automotive body modules, critical µP power monitoring, and portable medical devices requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for MAX691AEJE 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, mixed-signal, and power management ICs for industrial, automotive, and computing applications.

The MAX690–MAX695 family was engineered specifically to consolidate µP supervision functions-including reset, battery switchover, watchdog, PFI, and CE gating-into single-chip solutions for space- and reliability-critical embedded systems.

FAQ

What is the operating temperature range of the MAX691AEJE?

The MAX691AEJE carries the 'E' suffix, specifying an operating temperature range of –40°C to +85°C. This rating is validated per Maxim's production test flow and applies across all specified electrical parameters including reset threshold accuracy, watchdog timeout stability, and battery switchover hysteresis. The device meets MIL-STD-883 thermal cycling requirements and is qualified for use in automotive under-hood and industrial control cabinet environments where ambient extremes occur.

Does the MAX691AEJE support adjustable reset timeout periods?

Yes, the MAX691AEJE supports two reset timeout periods: 50ms and 200ms. Selection is controlled by the OSC SEL and OSC IN pin states per Table 1 in the datasheet. When OSC SEL is floating and OSC IN is low, the timeout is 50ms; when OSC SEL is floating and OSC IN is floating, it is 200ms. This configurability allows designers to match reset duration to specific microprocessor oscillator startup times without external components.

How does the MAX691AEJE handle battery switchover hysteresis?

The MAX691AEJE implements 20mV hysteresis in its battery switchover comparator. Switchover occurs at VCC – VBATT = 70mV when VCC rises, and at 50mV when VCC falls. This prevents oscillatory switching during slow VCC decay near VBATT voltage, ensuring stable VOUT delivery to CMOS RAM. The hysteresis is factory-trimmed and remains stable over temperature and voltage, eliminating need for external hysteresis networks.

Can the MAX691AEJE be used with lithium backup batteries?

Yes, the MAX691AEJE is explicitly designed for lithium coin-cell backup (e.g., CR2032). Its VBATT input accepts 2.0V–4.25V, and its internal charging current is limited to 0.1µA maximum-well below safe charging limits for all common lithium chemistries. The datasheet confirms compatibility with lithium cells, noting that the 10nA typical outflow from VBATT compensates for self-discharge without risk of overcharge or dendrite formation.

What is the function of the CE OUT pin on the MAX691AEJE?

The CE OUT pin on the MAX691AEJE is a chip-enable gating output that follows CE IN only when VCC remains above the 4.65V reset threshold. If VCC drops below this level-even momentarily-CE OUT is forced high independently of CE IN state. This action disables writes to battery-backed CMOS RAM or EEPROM, preventing data corruption during power-up, brownout, or shutdown. Propagation delay is 50–200ns, ensuring sub-microsecond protection engagement.