Analog Devices Inc./Maxim Integrated MAX709MEPA+

Overview

MAX709MEPA+ from Maxim Integrated is a precision power-supply monitor IC with active-low reset output, designed for +3.3V and +5V microprocessor systems. It asserts RESET when VCC falls below 4.40V (±150mV), holds reset for ≥140ms after VCC recovers, and operates down to 1V supply. Its 8-pin plastic DIP package supports industrial temperature range (–40°C to +85°C) and eliminates external components in embedded power supervision.

For engineers reviewing the MAX709MEPA+ datasheet, MAX709MEPA+ pinout, MAX709MEPA+ application, or MAX709MEPA+ equivalent, key selection criteria include reset threshold accuracy (4.40V nominal), guaranteed reset assertion at VCC ≥1V, immunity to short negative VCC transients (<40µs at 100mV overdrive), and compatibility with bidirectional µP reset I/O via series resistor.

Technical Context

The MAX709MEPA+ integrates a precision voltage comparator, internal timing capacitor, and open-drain RESET driver. Its reset threshold is factory-trimmed to 4.40V (M-suffix), with ±150mV tolerance over –40°C to +85°C, and exhibits <0.3% typical drift across temperature.

It delivers a minimum 140ms reset timeout after VCC rises above threshold, with no external timing components required. The RESET output sinks up to 1.2mA at VCC = reset threshold min and remains valid down to VCC = 1V; below 1V, RESET becomes high-impedance.

Key Specifications

Pinout & Package

MAX709MEPA+ uses an 8-pin plastic DIP (dual in-line package) with 0.3-inch body width and through-hole mounting. Pin 1 is top-left corner (notch side), pin 8 is top-right.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar power-supply monitor applications.

Compared with MAX706MEPA+, the MAX709MEPA+ omits manual reset for reduced pin count and BOM cost; compared with TPS3808G33DBVR, it provides higher reset threshold and proven transient immunity in legacy +5V industrial systems, but lacks adjustable timeout or enable control.

Availability

MAX709MEPA+ is available at Aetrix Electronics and suitable for industrial PLC controllers, medical diagnostic instruments, automotive body control modules, smart energy meters, and embedded instrumentation requiring stable component supply across extended temperature ranges.

Supply support for MAX709MEPA+ 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 and mixed-signal ICs for industrial, automotive, and communications applications, emphasizing reliability, integration, and low-power operation.

The MAX709MEPA+ belongs to Maxim's µP supervisory circuit family, engineered specifically for deterministic power-on/power-down reset generation in microprocessor-based systems without external timing components.

FAQ

What is the exact reset threshold voltage for MAX709MEPA+?

The MAX709MEPA+ has a factory-trimmed nominal reset threshold of 4.40V, with guaranteed limits of 4.25V (min) and 4.50V (max) over the full –40°C to +85°C operating range. This value is specified in the Electrical Characteristics table under "RESET Threshold, VTH" for suffix M. The threshold remains stable across temperature with <0.3% typical drift, making MAX709MEPA+ suitable for precise +5V and +3.3V system supervision.

Does MAX709MEPA+ require external components to function?

No, the MAX709MEPA+ requires no external components for basic reset functionality. It integrates a precision voltage reference, comparator, and timing capacitor. A 0.1µF ceramic bypass capacitor on VCC (pin 2) is recommended for noise immunity but is not strictly required for operation. Unlike discrete solutions, MAX709MEPA+ eliminates external resistors, capacitors, and diodes-reducing BOM count and PCB area while improving reliability.

Can MAX709MEPA+ drive a microprocessor reset pin directly?

Yes, the MAX709MEPA+ RESET output (pin 7) is an open-drain driver capable of sinking up to 1.2mA at VCC = 4.25V, which is sufficient to drive standard CMOS and TTL reset inputs. An external pull-up resistor (typically 10kΩ to VCC) is required. For µPs with bidirectional reset I/O (e.g., Motorola 68HC11), a 4.7kΩ series resistor between MAX709MEPA+ RESET and the µP pin prevents contention and ensures clean logic levels.

What is the minimum supply voltage at which MAX709MEPA+ guarantees RESET assertion?

The MAX709MEPA+ guarantees correct RESET output state down to VCC = 1.0V. Below this voltage, the RESET pin transitions to high-impedance (open-circuit) and no longer actively pulls low. This behavior is intentional: most µPs are nonfunctional below 1V, so MAX709MEPA+ maintains supervision integrity across the critical operating window where reset action is meaningful. For applications requiring RESET validity down to 0V, a 100kΩ pull-down resistor on the RESET line is recommended.

How does MAX709MEPA+ handle short negative transients on the VCC line?

The MAX709MEPA+ is specifically designed to reject short negative-going VCC transients. For a 100mV overdrive (i.e., VCC dipping 100mV below the 4.40V threshold), it tolerates transients up to 40µs in duration without issuing a false reset pulse. This immunity is confirmed in Figure 1 of the datasheet and stems from internal filtering and comparator hysteresis. Adding a 0.1µF bypass capacitor at VCC (pin 2) further enhances noise rejection, making MAX709MEPA+ robust in electrically noisy environments like motor controls or automotive systems.