Analog Devices Inc./Maxim Integrated MAX704REPA+

Overview

MAX704REPA+ from Maxim Integrated is a 3.0V/3.3V microprocessor supervisory circuit with active-low RESET output, 2.625V reset threshold (R-suffix), 200ms reset timeout, watchdog timer (1.6s), and battery-backup switchover capability. It monitors VCC supply integrity, asserts reset during brownout or watchdog timeout, and switches CMOS RAM to VBATT when VCC falls below 2.40V - used in embedded controllers and portable equipment requiring reliable power-fail detection and nonvolatile memory retention.

For engineers reviewing the MAX704REPA+ datasheet, MAX704REPA+ pinout, MAX704REPA+ application, or MAX704REPA+ equivalent, key selection criteria include reset threshold tolerance (±4%), battery leakage current (≤0.5µA), guaranteed RESET assertion down to VCC = 1V, PFI comparator accuracy (±75mV), and compatibility with lithium backup batteries exceeding VCC in normal operation.

Technical Context

The MAX704REPA+ integrates a precision voltage monitor with hysteresis (10mV typical), a 1.6s watchdog timer that clears on WDI edge transitions, and a dual-path power switch: VCC-to-VOUT via 3Ω PMOS and VBATT-to-VOUT via 140Ω NMOS. Its reset generator guarantees low-state duration ≥200ms after VCC rise, MR deassertion, or watchdog timeout.

It features independent power-fail detection (PFI input referenced to 1.237V ±75mV) and battery switchover logic that activates only when VCC < VSW (2.40V) *and* VBATT > VCC - preventing premature battery discharge while ensuring CMOS RAM retains data above 2.0V. The device operates across –40°C to +85°C in 8-pin SO package.

Key Specifications

Pinout & Package

MAX704REPA+ is housed in an 8-pin SOIC (Small Outline Integrated Circuit) package with standard 1.27mm pitch, RoHS-compliant lead-free finish (+ suffix), and moisture sensitivity level (MSL) 1.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX704SEPA+, MAX704REPA+ offers tighter timing alignment with 3.0V rails and longer battery runtime due to lower leakage; compared with MAX706REPA+, it adds critical watchdog supervision and seamless battery switchover - essential for unattended remote devices.

Availability

MAX704REPA+ is available at Aetrix Electronics and suitable for battery-powered computers and controllers, embedded controllers, intelligent instruments, critical µP power monitoring, and portable equipment requiring stable component supply across industrial temperature ranges.

Supply support for MAX704REPA+ 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, communications, and computing markets.

The MAX704 series belongs to Maxim's microprocessor supervisory product line, engineered specifically for robust power monitoring and battery-backed memory retention in 3.0V/3.3V µP systems operating from –40°C to +85°C.

FAQ

What is the exact reset threshold voltage for MAX704REPA+?

The MAX704REPA+ has a nominal reset threshold voltage of 2.625V, with a tolerance of ±4% over temperature and supply variations. This value applies to both rising and falling VCC edges, though hysteresis ensures the rising threshold is slightly higher (2.635V typ) to prevent oscillation during recovery. The R-suffix explicitly denotes this 2.625V variant within the MAX704 family.

Does MAX704REPA+ support battery voltages higher than VCC?

Yes, MAX704REPA+ explicitly supports VBATT exceeding VCC - a core design feature enabling direct connection of 3.6V lithium coin cells without series diodes. The internal battery switchover circuit activates only when VCC falls below 2.40V (VSW) and VBATT > VCC, ensuring zero forward-voltage drop and full battery utilization during backup mode.

Can the watchdog timer in MAX704REPA+ be disabled?

No, the watchdog timer in MAX704REPA+ cannot be disabled. It is permanently enabled and triggers a reset if the WDI pin remains static (high or low) for more than 1.6 seconds. The timer clears only on rising or falling edges at WDI or during active RESET assertion - making it suitable for safety-critical applications requiring mandatory firmware supervision.

What is the maximum allowable VCC transient duration that will not trigger reset in MAX704REPA+?

For a VCC transient 100mV below the 2.625V reset threshold (i.e., 2.525V), MAX704REPA+ tolerates negative-going glitches up to 40µs without issuing a reset pulse. This immunity is enhanced by internal filtering and a 100nF bypass capacitor recommended at the VCC pin - critical for noisy industrial power rails.

How does MAX704REPA+ handle power-fail detection for auxiliary supplies?

MAX704REPA+ uses the PFI pin to monitor auxiliary supplies via an external resistor divider, comparing the scaled voltage to a precise 1.237V internal reference (±75mV accuracy). When PFI falls below this threshold, PFO goes low - enabling interrupt generation or cascaded reset assertion via connection to MR on compatible variants like MAX704REPA+ itself.