Analog Devices Inc./Maxim Integrated MAX691CPE+

Overview

The MAX691CPE+ from Maxim Integrated is a 16-pin CMOS microprocessor supervisory circuit that integrates reset generation, watchdog timer, battery backup switchover, power-fail detection, and chip-enable gating for systems requiring high-reliability power monitoring. 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 +5V (VCC) and 2.0–4.25V backup battery (VBATT). It is used in industrial controllers and intelligent instruments to prevent data corruption during brownouts.

For engineers reviewing the MAX691CPE+ datasheet, MAX691CPE+ pinout, MAX691CPE+ application, or MAX691CPE+ equivalent, key selection criteria include its active-low RESET with hysteresis, battery switchover threshold (70mV rise / 50mV fall), CE OUT write-protection logic, dual-mode oscillator control (internal/external), and compatibility with 5V ±5% supplies.

Technical Context

The MAX691CPE+ implements a precision voltage monitor with 4.65V ±150mV reset threshold and 40mV hysteresis, ensuring stable reset assertion across temperature. Its internal bandgap reference feeds both the reset comparator and 1.3V power-fail detector, enabling coordinated system-level fault response.

It uses a dual-path timing architecture: an internal 6.55kHz oscillator (or external clock/capacitor on OSC IN/OSC SEL) controls both reset delay and watchdog timeout independently. The CE gating circuit forces CE OUT high when VCC drops below 4.65V, decoupling RAM write enable from software state during supply transients.

Key Specifications

Pinout & Package

MAX691CPE+ is housed in a 16-pin plastic DIP (Dual In-line Package) with 0.3-inch body width and through-hole mounting. Pin pitch is 0.1 inch; lead finish is tin-lead.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX695CPE+, MAX691CPE+ provides identical timing and protection features at fixed 4.65V threshold, simplifying qualification; versus TPS3823MPW, it delivers complete power supervision including switchover, CE gating, and dual fault signaling - essential for data-critical embedded systems.

Availability

MAX691CPE+ is available at Aetrix Electronics and suitable for industrial controllers, intelligent instruments, automotive body modules, and critical µP power monitoring applications requiring stable component supply, long-term lifecycle support, and traceable sourcing.

Supply support for MAX691CPE+ 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, watchdog, and battery-switch circuits in µP-based systems - delivering board-space savings, improved reliability, and guaranteed timing behavior under voltage transients.

FAQ

What is the reset threshold voltage of the MAX691CPE+ and how does it behave over temperature?

The MAX691CPE+ has a guaranteed reset threshold of 4.65V ±150mV over the full operating temperature range (0°C to +70°C for C-suffix). Its internal bandgap reference ensures monotonic performance with typical hysteresis of 40mV, preventing chatter during slow VCC recovery. This makes MAX691CPE+ compatible with standard +5V ±5% power supplies while maintaining immunity to noise-induced false resets.

How does the MAX691CPE+ handle battery backup switchover, and what is the switchover threshold?

The MAX691CPE+ switches VOUT between VCC and VBATT based on relative voltage levels, with a rising-edge switchover threshold of (VCC − VBATT) = +70mV and falling-edge threshold of +50mV. This 20mV hysteresis prevents oscillation during slow supply transitions. In battery mode, MAX691CPE+ draws only 1µA, enabling multi-year retention with standard coin cells - confirmed in the Electrical Characteristics table under "Supply Current in Battery Backup Mode".

Can the MAX691CPE+ be used without an external backup battery?

Yes - the MAX691CPE+ operates fully without a backup battery. Connect VBATT to GND and tie VOUT to VCC. All supervisory functions (reset, watchdog, PFI/PFO, CE gating) remain active. The battery switchover circuit is disabled, and MAX691CPE+ behaves as a pure 5V supervisor. This configuration is explicitly supported in the Typical Applications section and Pin Description table.

What is the function of the CE IN and CE OUT pins on the MAX691CPE+?

CE IN accepts the system's chip-enable signal; CE OUT replicates it when VCC ≥ 4.65V, but forces high when VCC drops below threshold - blocking RAM writes during brownouts. This hardware-enforced write protection is a core feature of MAX691CPE+ and eliminates need for external logic. Propagation delay is 50ns (typical), as specified in the "CHIP ENABLE GATING" section of the Electrical Characteristics table.

Does the MAX691CPE+ support external clock input for the watchdog timer?

Yes - when OSC SEL is driven low, the MAX691CPE+ accepts an external clock signal on OSC IN (0–250kHz), enabling precise, system-synchronized watchdog timeout control. This mode allows timeout periods defined in clock cycles (e.g., 1024 or 4096 cycles), as detailed in Table 1. The internal oscillator remains disabled in this configuration, giving full timing control to the host system.