Analog Devices Inc./Maxim Integrated MAX703EPA+

Overview

MAX703EPA+ from Maxim Integrated is a precision microprocessor supervisory circuit in 8-pin PDIP package, providing active-low reset (4.65V threshold), battery-backup switching, 1.25V power-fail comparator input, and debounced manual reset - used to ensure reliable startup and brownout recovery in industrial controllers and embedded systems.

For engineers reviewing the MAX703EPA+ datasheet, MAX703EPA+ pinout, MAX703EPA+ application, or MAX703EPA+ equivalent, key selection criteria include guaranteed RESET assertion down to VCC = 1V, 200ms reset pulse width, 50nA battery-backup quiescent current, and −40°C to +85°C operating range for harsh-environment deployment.

Technical Context

The MAX703EPA+ integrates four core functions in a single IC: a precision voltage monitor with 4.65V ±150mV reset threshold, a battery switchover circuit with 40mV hysteresis and 80Ω p-channel MOSFET output switch, a 1.25V reference-based power-fail comparator (PFI/PFO), and TTL/CMOS-compatible manual reset with internal 250µA pullup.

It operates across VCC = 0–5.5V and VBATT = 0–6.0V, asserts RESET low during power-up/down/brownout, maintains valid RESET output even as VCC falls to 1V, and disables PFI/PFO functionality in battery-backup mode to reduce leakage.

Key Specifications

Pinout & Package

MAX703EPA+ uses an 8-pin plastic dual in-line package (PDIP) with standard through-hole footprint and RoHS-compliant lead(Pb)-free finish (indicated by "+" suffix).

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX704EPA+, the MAX703EPA+ offers higher reset threshold for improved noise immunity in stable +5V systems; compared with MAX705CPA+, it trades watchdog functionality for essential battery-switchover in long-term data retention applications.

Availability

MAX703EPA+ is available at Aetrix Electronics and suitable for industrial PLC controllers, medical diagnostic equipment, automotive telematics gateways, and smart energy meters requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for MAX703EPA+ 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 high-performance analog and mixed-signal ICs for industrial, communications, and computing applications.

The MAX703/MAX704 family was engineered specifically for cost-sensitive microprocessor systems needing integrated power monitoring, reset generation, and battery-backed RAM support - without requiring external timing or switching components.

FAQ

What is the guaranteed reset assertion voltage for MAX703EPA+?

The MAX703EPA+ guarantees RESET output remains valid and actively driven low down to VCC = 1V, ensuring deterministic reset behavior during deep undervoltage events. This specification is confirmed in the Absolute Maximum Ratings and Electrical Characteristics tables of the official datasheet, and applies across the full −40°C to +85°C operating range. The MAX703EPA+ achieves this using internal charge-pump-assisted output drivers that remain functional well below typical logic thresholds.

Does MAX703EPA+ support lithium battery backup, and what is the maximum allowable VBATT voltage?

Yes, MAX703EPA+ supports direct connection of lithium batteries (2.8V–3.6V typical) to the VBATT pin. Per Table 2 in the datasheet, the maximum allowable backup-battery voltage is 4.80V to prevent substrate diode conduction and excessive leakage. Operation above this voltage risks reverse current flow into the VCC substrate when VCC is near the reset threshold, potentially degrading long-term reliability and increasing quiescent current beyond the specified 50nA.

How does the manual reset (MR) input behave in MAX703EPA+, and is external pull-up required?

The MR input of MAX703EPA+ is an active-low TTL/CMOS-compatible pin with an internal 250µA pullup current, so no external pull-up resistor is required. When pulled below 0.8V (e.g., by a pushbutton to ground), it initiates a full 200ms reset pulse - effectively debounced by the internal timer. Leaving MR floating results in a logic-high state due to the internal pullup, disabling manual reset. This design reduces BOM count and simplifies PCB layout for compact embedded systems.

Can MAX703EPA+ monitor negative supply voltages, and how is this implemented?

Yes, MAX703EPA+ can monitor negative supplies using an external resistor network that level-shifts the negative voltage to the PFI input. As shown in Figure 8 of the datasheet, connecting R1/R2 between V– and GND creates a positive voltage at PFI proportional to |V–|; when that voltage drops below 1.25V, PFO goes low. Accuracy depends on resistor tolerance, PFI input current (<25nA), and VCC stability. This technique enables fail-safe monitoring of −5V, −12V, or other negative rails without additional comparators.

What is the function of the PFO output in MAX703EPA+, and when is it disabled?

The PFO output in MAX703EPA+ is an open-drain active-low signal that goes low when the PFI input voltage falls below 1.25V - indicating power-fail or low-battery condition. It is explicitly disabled (forced low) when the device enters battery-backup mode (i.e., VCC < reset threshold and VBATT > VCC), as stated in the Detailed Description section and Table 1. This prevents spurious interrupts during backup operation and conserves power by turning off the comparator's bias circuitry.