Analog Devices Inc./Maxim Integrated MAX708REUA+

Overview

MAX708REUA+ from Maxim Integrated is a precision +3V microprocessor supervisory circuit in an 8-pin µMAX package, providing active-low RESET and active-high RESET outputs, 2.63V reset threshold, 200ms reset pulse width, and 1.25V power-fail comparator input - used to ensure reliable boot-up and brownout recovery in battery-powered portable instruments and industrial controllers.

For engineers reviewing the MAX708REUA+ datasheet, MAX708REUA+ pinout, MAX708REUA+ application, or MAX708REUA+ equivalent, key selection criteria include dual-reset polarity support, guaranteed RESET assertion down to VCC = 1V, low 100µA quiescent current, and compatibility with +3V/+5V supply systems requiring deterministic power monitoring without watchdog overhead.

Technical Context

The MAX708REUA+ integrates dual independent reset generators - one asserting active-low RESET and the other active-high RESET - both triggered by VCC falling below 2.63V (±1.5% tolerance) or MR assertion, with synchronized 200ms deassertion delay. It includes a dedicated 1.25V precision reference for external PFI voltage monitoring and guarantees valid reset output down to VCC = 1V.

Unlike the MAX706 series, the MAX708REUA+ omits the watchdog timer but adds complementary reset outputs, enabling direct interface to µPs requiring either polarity - eliminating external inverters. Its PFO output asserts low when PFI falls below 1.25V, supporting early power-fail warning and low-battery detection with <25nA input leakage.

Key Specifications

Pinout & Package

MAX708REUA+ uses the 8-pin µMAX package (package code U8-1), a surface-mount, lead-free-compatible 3mm × 3mm body with exposed pad for thermal performance. Pin numbering follows standard µMAX top-view orientation (pin 1 marked).

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX706REUA+, MAX708REUA+ trades watchdog capability for dual-reset polarity and retains full PFI/PFO functionality - making it optimal for heterogeneous processor interfaces. Versus TPS3808G12DBVR, it delivers essential power-fail warning at higher IQ but in a larger, functionally richer package.

Availability

MAX708REUA+ is available at Aetrix Electronics and suitable for portable medical monitors, industrial PLC I/O modules, smart energy meters, and ruggedized handheld testers requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for MAX708REUA+ 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 demanding industrial, automotive, and communications applications.

The MAX708 family was engineered specifically for cost-sensitive, space-constrained +3V µP systems needing deterministic power-on reset, brownout protection, and configurable power-fail warning - without watchdog complexity.

FAQ

What is the reset threshold voltage of the MAX708REUA+ and how tightly is it specified?

The MAX708REUA+ has a nominal reset threshold of 2.63V, with a guaranteed tolerance of ±1.5% over the full operating temperature range (-40°C to +85°C). This precision is achieved via laser-trimmed bandgap references and ensures consistent reset behavior across supply and thermal variations - critical for reliable operation in battery-powered equipment where voltage margins are narrow. The MAX708REUA+ maintains this specification without external calibration.

Does the MAX708REUA+ provide both active-high and active-low reset outputs simultaneously?

Yes, the MAX708REUA+ provides both RESET (active-low) and RESET (active-high) outputs concurrently. These signals are internally synchronized and deassert after the same 200ms delay once VCC rises above 2.63V or MR is released. This dual-output architecture eliminates the need for external inverters when interfacing with mixed-logic µPs or FPGAs - a key differentiator from the MAX706 series and many competing supervisors.

Can the MAX708REUA+ monitor a secondary power supply such as +12V or negative rails?

Yes, the MAX708REUA+ can monitor secondary supplies using its PFI input and internal 1.25V reference. For +12V, connect PFI to a resistive divider that scales the voltage so PFI = 1.25V at the desired trip point (e.g., 11V). For negative rails, use the Figure 8 configuration in the datasheet, where PFO asserts high when the negative supply drops. Accuracy depends on resistor tolerance and PFI input leakage (<25nA), not on VCC stability.

What is the minimum supply voltage at which MAX708REUA+ guarantees valid reset output assertion?

The MAX708REUA+ guarantees RESET and RESET assertion down to VCC = 1.2V (minimum specified), and the RESET output remains valid (logic-low) down to VCC = 1.0V. This is explicitly tested and guaranteed - unlike many competitors that cease driving below 2.0V. This feature ensures fail-safe behavior during deep brownouts common in battery-powered systems nearing end-of-life.

Is the MAX708REUA+ watchdog-enabled, and what alternatives include watchdog functionality?

No, the MAX708REUA+ does not include a watchdog timer - it is intentionally optimized for applications requiring only precise voltage monitoring and dual-reset outputs. For watchdog capability with the same 2.63V threshold and µMAX package, the MAX706REUA+ is the direct alternative. It adds WDI/WDO pins and a 1.6s timeout, but provides only a single RESET output (active-low), requiring external logic if active-high reset is also needed.