Analog Devices Inc./Maxim Integrated MAX708ESA+

Overview

The MAX708ESA+ from Maxim Integrated is a precision microprocessor supervisory circuit featuring active-high reset output, 4.40V supply-voltage monitor threshold, 1.6s watchdog timeout, 1.25V power-fail comparator input, and debounced manual-reset input - all in an 8-pin SO package. It ensures reliable power-up/power-down sequencing and brownout protection for 5V µP systems in industrial controllers and embedded instrumentation.

For engineers reviewing the MAX708ESA+ datasheet, MAX708ESA+ pinout, MAX708ESA+ application, or MAX708ESA+ equivalent, key selection criteria include its guaranteed RESET validity down to VCC = 1.2V, 200ms reset pulse width, ±40mV reset threshold hysteresis, and compatibility with TTL/CMOS logic interfaces without external pull-ups.

Technical Context

The MAX708ESA+ integrates four core supervisory functions: a precision voltage monitor triggering reset at 4.40V (±150mV), a 1.6s watchdog timer with edge-sensitive WDI input, a 1.25V reference-based power-fail comparator (PFI/PFO), and a debounced active-low manual-reset input (MR) with 250µA internal pull-up. Its active-high RESET output remains valid down to VCC = 1.2V, enabling robust reset assertion during deep brownout conditions.

Unlike the MAX705/MAX706 series, the MAX708ESA+ substitutes the watchdog output (WDO) with an active-high RESET signal - eliminating need for external inverters in µP systems requiring high-true reset (e.g., Intel 80C51). The PFI input draws only ±25nA, allowing high-impedance voltage-divider monitoring of auxiliary rails or battery voltage without loading errors.

Key Specifications

Pinout & Package

MAX708ESA+ is housed in an 8-pin SO (Small Outline) package, RoHS-compliant, with 1.27mm lead pitch and surface-mount footprint per outline 21-0041. Thermal dissipation rating is 471mW at +70°C (derates 5.88mW/°C above).

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX708ESA+, MAX708CSA offers identical electrical behavior but reduced thermal margin, while MAX813LESA trades lower reset threshold for integrated watchdog - making MAX708ESA+ optimal for wide-temperature industrial 5V systems needing robust brownout response without watchdog overhead.

Availability

MAX708ESA+ is available at Aetrix Electronics and suitable for industrial PLC controllers, medical diagnostic instruments, automotive body control modules, smart energy meters, and critical µP power monitoring applications requiring stable component supply across extended temperature ranges.

Supply support for MAX708ESA+ 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 markets.

The MAX705–MAX708/MAX813L product line was designed to replace discrete reset generators and voltage monitors in µP-based systems - delivering guaranteed timing, precision thresholds, and low-power operation in compact packages.

FAQ

What is the reset threshold voltage for MAX708ESA+?

The MAX708ESA+ has a nominal reset threshold of 4.40V with a tolerance of ±150mV. This means the active-high RESET output is asserted when VCC falls below approximately 4.25V and remains asserted until VCC rises above 4.55V, providing hysteresis to prevent chatter during marginal supply conditions. This threshold is factory-trimmed and guaranteed over the full -40°C to +85°C operating range.

Does MAX708ESA+ include a watchdog timer function?

No, the MAX708ESA+ does not include a watchdog timer. Unlike the MAX705/MAX706/MAX813L variants, the MAX708ESA+ replaces the watchdog output (WDO) with a second reset output (active-low RESET), retaining only the power-fail comparator (PFI/PFO) and manual-reset (MR) functions. Its block diagram confirms absence of watchdog timer circuitry - verified in Maxim's official datasheet Figure 2.

Can MAX708ESA+ operate with supply voltages below 5V?

Yes, MAX708ESA+ operates from VCC = 1.2V to 5.5V. Its RESET outputs remain fully functional down to 1.2V, and the internal voltage monitor continues to assert reset as long as VCC stays below 4.40V. This capability supports brownout recovery in battery-powered systems where VCC may sag to 1.8V or lower before shutdown - confirmed in Electrical Characteristics Table, row "Operating Voltage Range".

What is the purpose of the PFI and PFO pins on MAX708ESA+?

The PFI (Power-Fail Input) pin accepts an external voltage - typically from a resistor divider - and compares it to an internal 1.25V reference. When PFI falls below 1.25V, the PFO (Power-Fail Output) pin goes low, signaling impending power loss or low battery. This allows µP systems to initiate graceful shutdown or data save routines. PFO is open-drain and can sink up to 3.2mA, enabling direct interface with µP interrupt inputs.

Is MAX708ESA+ pin-compatible with other MAX70x devices in SO package?

Yes, MAX708ESA+ shares identical 8-pin SO pinout with MAX705ESA+, MAX706ESA+, MAX707ESA+, and MAX813LESA+. Pin assignments for VCC, GND, MR, PFI, PFO, RESET, RESET, and WDO are consistent across the family. However, functional differences exist: MAX708ESA+ uses pins 6 and 7 for dual RESET outputs and omits WDO functionality, whereas MAX705ESA+ uses pin 8 for WDO and pin 7 for RESET - requiring schematic review before substitution.