Analog Devices Inc./Maxim Integrated MAX704SEPA+

Overview

MAX704SEPA+ from Maxim Integrated is a 3.3V/3.0V microprocessor supervisory circuit with active-low RESET output, 2.925V reset threshold (S-suffix), 200ms reset timeout, watchdog timer (1.6s), and battery-backup switchover. It monitors VCC supply integrity, asserts reset during brownout or watchdog timeout, and switches VOUT to VBATT when VCC falls below 2.40V-enabling reliable CMOS RAM retention in portable controllers.

For engineers reviewing the MAX704SEPA+ datasheet, MAX704SEPA+ pinout, MAX704SEPA+ application, or MAX704SEPA+ equivalent, this page delivers verified specifications, validated pin functions, confirmed use cases in battery-backed embedded systems, and two technically documented alternative parts for 3.0V/3.3V µP supervision with manual reset and power-fail warning.

Technical Context

The MAX704SEPA+ integrates a precision reset comparator with ±4% threshold tolerance (2.925V nominal), a 1.6s watchdog timer that clears on WDI edge transitions, and a dual-path power-switching circuit: a 3Ω PMOS switch connects VCC to VOUT during normal operation, while a 140Ω NMOS switch engages VBATT-to-VOUT when VCC drops below VSW (2.40V). Its PFI input accepts external voltage dividers for auxiliary supply monitoring, with 1.237V internal reference and 10mV hysteresis.

RESET assertion is guaranteed down to VCC = 1V, and the device maintains valid reset behavior across -40°C to +85°C (E-grade). Battery current is limited to 1µA typical, and VCC supply current is 40µA at VCC < 3.6V-enabling long-term operation in low-power embedded systems without compromising reset timing accuracy or switchover reliability.

Key Specifications

Pinout & Package

MAX704SEPA+ is housed in an 8-pin plastic DIP (PDIP) package with 0.300" wide body, RoHS-compliant lead finish (+ suffix), and standard through-hole mounting. Pin spacing conforms to JEDEC MS-001.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX704SEPA+, MAX706SEPA+ removes watchdog capability but retains identical reset behavior and battery switchover-ideal for cost-sensitive designs without firmware supervision needs-while MAX809SEUR+T sacrifices all auxiliary functions for minimal footprint and lower quiescent current, making it suitable only for simple reset-only use cases.

Availability

MAX704SEPA+ is available at Aetrix Electronics and suitable for battery-powered portable controllers, industrial embedded data loggers, intelligent medical instrumentation, and critical µP power monitoring in POS terminals requiring stable component supply, long-term lifecycle support, and RoHS-compliant through-hole packaging.

Supply support for MAX704SEPA+ 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 applications.

The MAX704 series belongs to Maxim's microprocessor supervisory product line, designed specifically for reliable power monitoring and reset generation in 3.0V/3.3V battery-backed embedded systems requiring manual reset, watchdog supervision, and seamless backup power switchover.

FAQ

What is the exact reset threshold voltage for MAX704SEPA+?

The MAX704SEPA+ has a nominal reset threshold voltage of 2.925V (S-suffix), specified as 2.85V (min) to 3.00V (max) for VCC falling, with ±4% tolerance. This value is guaranteed across the full -40°C to +85°C operating temperature range and ensures reset assertion before the 3.3V supply falls below 2.85V, aligning with typical 3.3V ±10% system tolerances.

Does MAX704SEPA+ include a watchdog timer, and how is it cleared?

Yes, MAX704SEPA+ includes a 1.6s watchdog timer (tWD = 1.12–2.24s). It is cleared automatically on any rising or falling edge at the WDI pin, or while RESET is asserted. The timer starts counting only after RESET is deasserted. Unlike older families, the watchdog function cannot be disabled-ensuring continuous supervision of firmware execution in safety-critical applications.

How does the battery switchover work on MAX704SEPA+, and what is the switchover voltage?

MAX704SEPA+ switches VOUT from VCC to VBATT when VCC falls below 2.40V (VSW), ensuring CMOS RAM remains powered above its 2.0V minimum retention voltage. Switchover uses a 140Ω NMOS switch, limiting voltage drop under 1mA load to <140mV. When VCC recovers, VOUT reconnects to VCC only after VCC rises above the 2.925V reset threshold-preventing premature reversion during unstable recovery.

Can MAX704SEPA+ operate without a backup battery, and how should pins be configured?

Yes, MAX704SEPA+ can operate without a backup battery: connect both VBATT and VOUT pins directly to VCC. This disables battery switchover and power-fail comparator functionality (PFI/PFO remain usable). Do not leave VBATT floating-tying it to VCC ensures internal circuitry operates correctly and avoids undefined behavior in the battery-switch control path.

What is the maximum allowable negative-going VCC transient duration that will not trigger a reset on MAX704SEPA+?

At 100mV overdrive (i.e., VCC dropping 100mV below the 2.925V reset threshold), MAX704SEPA+ tolerates negative-going transients up to 40µs without issuing a reset pulse. This immunity is enhanced by a 100nF bypass capacitor placed near the VCC pin. Transient rejection improves with smaller overdrive magnitudes and degrades as overdrive increases-ensuring robust operation against common power rail noise.