Analog Devices Inc./Maxim Integrated MAX706SEPA+

Overview

MAX706SEPA+ from Maxim Integrated is an active-low microprocessor supervisory circuit designed for +3V to +5V systems, providing reset generation during power-up/down/brownout (2.93V threshold), 1.6s watchdog timeout, 1.25V power-fail comparator input, and debounced manual-reset input. It operates over –40°C to +85°C in 8-pin PDIP package and is used in battery-powered portable instruments requiring reliable µP reset control.

For engineers reviewing the MAX706SEPA+ datasheet, MAX706SEPA+ pinout, MAX706SEPA+ application, or MAX706SEPA+ equivalent, key selection criteria include its fixed 2.93V reset threshold, guaranteed RESET assertion down to VCC = 1V, 200ms reset pulse width, and compatibility with TTL/CMOS logic levels across supply voltages from 2.7V to 5.5V.

Technical Context

The MAX706SEPA+ integrates a precision voltage monitor, a 1.6s watchdog timer with WDI transition detection, a 1.25V reference-based power-fail comparator (PFI/PFO), and a 70µA internal MR pullup. Its reset generator asserts active-low RESET for ≥200ms after VCC rises above 2.93V or MR is released.

Unlike the MAX706AP/AR/AS/AT family, the MAX706SEPA+ watchdog cannot be disabled - WDI must be toggled within 1.6s to prevent WDO assertion. The device guarantees RESET output functionality down to VCC = 1V and supports operation with both +3V and +5V supplies while maintaining specified timing and drive strength.

Key Specifications

Pinout & Package

MAX706SEPA+ is housed in an 8-pin plastic DIP (PDIP) package (package code P8-1), lead-free compliant, with 0.3-inch body width and through-hole mounting.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX706SEPA+, MAX706SESA+ offers identical functionality in a space-saving SO package, while MAX706REPA+ shifts reset activation to 2.63V - enabling earlier intervention in lower-voltage or higher-tolerance designs, but requiring validation against the target µP's minimum operating voltage.

Availability

MAX706SEPA+ is available at Aetrix Electronics and suitable for battery-powered equipment, portable instruments, and industrial controllers requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for MAX706SEPA+ 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, computing, and communications markets.

The MAX706 family was designed specifically for cost-sensitive, space-constrained µP supervisory applications requiring precision voltage monitoring, watchdog safety, and robust reset timing - targeting portable, medical, and industrial embedded systems.

FAQ

What is the reset threshold voltage of the MAX706SEPA+?

The MAX706SEPA+ has a fixed reset threshold of 2.93V (VCC falling), with ±70mV tolerance over temperature. This value is factory-trimmed and guaranteed across the –40°C to +85°C operating range. The MAX706SEPA+ asserts active-low RESET whenever VCC drops below this threshold and holds it for ≥200ms after VCC rises above it. This threshold is optimized for +3.3V microprocessor systems and is distinct from other variants like MAX706REPA+ (2.63V) or MAX706TEPA+ (3.08V).

Does the MAX706SEPA+ include a watchdog timer, and can it be disabled?

Yes, the MAX706SEPA+ includes a 1.6s watchdog timer monitored via the WDI pin. However, unlike the MAX706AP/AR/AS/AT variants, the watchdog function in MAX706SEPA+ cannot be disabled - WDI must be toggled within 1.6s to prevent WDO from asserting low. Leaving WDI open or floating will cause continuous WDO timeout. This design ensures fail-safe behavior in safety-critical applications where watchdog supervision must remain active at all times.

What is the purpose of the PFI and PFO pins on the MAX706SEPA+?

The PFI (Power-Fail Input) pin connects to an external resistive divider to monitor a secondary supply (e.g., unregulated battery or DC-DC input), comparing it against an internal 1.25V reference. When the divided voltage falls below 1.25V, the PFO (Power-Fail Output) pin goes active-low to signal impending supply failure. In MAX706SEPA+, PFO can be tied to MR to generate a controlled reset before main supply collapse, enabling orderly shutdown - a key feature in portable and medical devices using MAX706SEPA+.

Can the MAX706SEPA+ operate with a 5V supply, and how does performance change?

Yes, the MAX706SEPA+ operates across 2.7V to 5.5V. At 5V, MR input thresholds rise to VIH = 2.0V and VIL = 0.8V, WDO and RESET output drive improves (VOL ≤ 0.4V at 3.2mA sink), and MR pulse width minimum reduces to 150ns. Quiescent current increases slightly (to ~200µA typ), but all timing parameters (200ms reset, 1.6s watchdog) remain unchanged. This dual-voltage capability makes MAX706SEPA+ suitable for systems transitioning between +3.3V and +5V operation without redesign.

Is the MAX706SEPA+ pin-compatible with other MAX706 variants?

Yes, all MAX706P/R/S/T and MAX706AP/AR/AS/AT variants share identical 8-pin PDIP (P8-1), SO (S8-2), and µMAX (U8-1) footprints and pinouts - including MAX706SEPA+. Pin 1 is MR, Pin 7 is RESET, Pin 6 is WDO, and Pin 8 is WDI. However, functional differences exist: MAX706SEPA+ provides active-low RESET only and non-disableable watchdog, whereas MAX706PEPA+ offers active-high RESET and MAX708SEPA+ provides both RESET and RESET outputs. Electrical compatibility requires verifying reset threshold and output polarity for the target application.