Analog Devices Inc./Maxim Integrated MAX691ACPE

Overview

The MAX691ACPE from Maxim Integrated is a microprocessor supervisory circuit in a 16-pin plastic DIP package, providing power-on reset, watchdog timer, battery switchover, chip-enable gating, and power-fail monitoring. It features a 4.65V typical reset threshold, 200ms reset timeout, 30μA operating supply current, and guaranteed RESET assertion down to VCC = 1V - enabling reliable μP startup and brownout protection in embedded controllers and intelligent instruments.

For engineers reviewing the MAX691ACPE datasheet, MAX691ACPE pinout, MAX691ACPE application, or MAX691ACPE equivalent, this device delivers verified reset timing accuracy, low-power battery-backup operation (1μA standby), integrated CE signal protection, and ±2% power-fail comparator accuracy - critical for industrial control, medical instrumentation, and legacy system power management where deterministic reset behavior and nonvolatile memory write protection are required.

Technical Context

The MAX691ACPE implements dual reset outputs (active-low RESET and active-high RESET), an independent watchdog timer with selectable timeout periods (100ms or 1.6s), and a battery switchover comparator that activates when VCC falls below VBATT − 0.3V. Its internal oscillator sets timing without external components unless configured for capacitor- or clock-driven modes via OSC SEL/OSC IN.

It integrates a 75Ω series transmission gate for CE IN-to-CE OUT signal gating with ≤10ns propagation delay, a 1.25V precision power-fail comparator (PFI/PFO) with 25μs response, and a BATT ON output that transitions high during battery-backup mode - all operating across 0°C to +70°C with VCC = 4.75V to 5.5V and VBATT ≥ 2.0V.

Key Specifications

Pinout & Package

MAX691ACPE is housed in a 16-pin plastic DIP (dual in-line package) with 0.3-inch body width, through-hole mounting, and industry-standard pin spacing (0.1" pitch). Pin 1 is marked by a notch or dot; pin numbering follows standard DIP convention (counterclockwise from top-left).

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX691AEPE, the MAX691ACPE trades extended temperature operation for lower cost in commercial environments; versus TPS3823-46DBVT, it provides full feature integration (watchdog, CE gating, dual reset, battery switchover) at the expense of higher pin count and design complexity.

Availability

MAX691ACPE is available at Aetrix Electronics and suitable for industrial PLC controllers, medical diagnostic instruments, legacy embedded test equipment, and energy meter data loggers requiring stable component supply, long-term obsolescence management, and RoHS-compliant through-hole packaging.

Supply support for MAX691ACPE 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, communications, and computing markets.

The MAX691A family was designed specifically for robust microprocessor supervision in mission-critical embedded systems - integrating reset, watchdog, memory protection, and power-fail monitoring in a single 16-pin package.

FAQ

What is the reset threshold voltage of the MAX691ACPE, and how does it behave over temperature?

The MAX691ACPE has a typical reset threshold voltage of 4.65V, with a guaranteed range of 4.50V to 4.75V across 0°C to +70°C. Its temperature coefficient is tightly controlled, exhibiting only ±15mV variation (typical) over the full operating range - confirmed by Figure TOC-07 in the datasheet. This stability ensures consistent reset timing in industrial environments where rail voltage drift may occur.

Does the MAX691ACPE support battery backup, and what are the voltage and current limits on VBATT?

Yes, the MAX691ACPE supports battery backup via the VBATT pin, which accepts 2.0V to 5.5V. In battery-backup mode, it delivers up to 25mA continuous current from VBATT to VOUT, with peak capability of 250mA during power-up transients. The VBATT-to-VOUT on-resistance is 15Ω (at 4.5V), rising to 30Ω at 2.0V - values validated in Electrical Characteristics Table on page 2 of the datasheet.

How does the watchdog function operate on the MAX691ACPE, and can it be disabled?

The MAX691ACPE watchdog monitors the WDI pin: if no transition (high→low, low→high, or ≥100ns pulse) occurs within the timeout period (1.6s nominal), WDO and both RESET outputs assert for 200ms. The watchdog is disabled by leaving WDI floating - its internal 100kΩ divider biases it to ~1.6V, disabling the timer. This behavior is explicitly documented in the "Watchdog Input" section of the datasheet.

What is the purpose of the CE IN and CE OUT pins on the MAX691ACPE, and how do they protect memory?

The CE IN and CE OUT pins 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 failure), CE OUT is forced high-impedance or pulled to VOUT, blocking all CE signals to external CMOS RAM/EEPROM. This prevents corrupted writes during unstable power - a core function verified in the "Chip-Enable Signal Gating" section and Figure 4 block diagram.

Can the MAX691ACPE generate accurate power-fail warnings, and what is the PFI threshold tolerance?

Yes, the MAX691ACPE provides a precision power-fail comparator with PFI threshold of 1.25V ±2% over temperature - guaranteed for MAX691A/MAX800L variants per Electrical Characteristics table. This enables reliable low-battery detection or early AC line failure warning without external calibration. PFO asserts low when PFI falls below threshold, with 25μs typical response time from falling edge - confirmed in the "Power-Fail Comparator" section.