Analog Devices Inc./Maxim Integrated MAX689EPA

Overview

The MAX689EPA from Maxim Integrated is a precision 3.0V fixed-output low-dropout linear regulator requiring an external PNP pass transistor, delivering up to 1A output current with 40mV dropout at 200mA (FZT749), ±2% output accuracy, and active-low shutdown control. It operates from 2.7V to 11.0V input, features power-fail monitoring (PFO), and targets battery-powered portable instruments and memory backup supplies.

For engineers reviewing the MAX689EPA datasheet, MAX689EPA pinout, MAX689EPA application, or MAX689EPA equivalent, this page delivers verified electrical parameters, package mapping to 8-pin plastic DIP, confirmed shutdown threshold (1.25V ON, 1.2V standby entry), PFO open-drain behavior, and real-world transient response data for embedded power design validation.

Technical Context

The MAX689EPA implements a precision bandgap reference and comparator-based control loop that drives an external PNP transistor via its BASE pin, with base current limited by a resistor between BASE and BLIM (IBASE ≤ 0.1V / (RB + 5Ω)). Its SHDN input enables three-level operation: ON (>1.25V), standby (<1.2V, I_IN < 25µA), and full shutdown (<0.2V, I_IN < 1µA).

PFO is an open-drain output that asserts low when V_OUT drops 170mV below nominal (2.83V at 3.0V output), with 7mV hysteresis. The device lacks automatic latched shutdown-unlike MAX687-but provides precise, hysteresis-stabilized shutdown control suitable for system-level power sequencing in industrial and portable equipment.

Key Specifications

Pinout & Package

MAX689EPA is housed in an 8-pin plastic DIP package (0.300" wide), rated for −40°C to +85°C operation, with through-hole mounting and industry-standard lead pitch (0.100").

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar low-dropout linear regulator applications.

Compared with MAX688EPA, MAX689EPA provides 3.0V output essential for low-voltage memory and sensors, while LT1528CS8#PBF eliminates external transistor complexity but sacrifices PFO functionality and 3.0V accuracy-making MAX689EPA optimal for precision, battery-sensitive 3.0V applications requiring fault signaling.

Availability

MAX689EPA is available at Aetrix Electronics and suitable for portable instrumentation, battery-backed memory systems, and low-power wireless sensor nodes requiring stable component supply across extended temperature ranges (−40°C to +85°C).

Supply support for MAX689EPA 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 power management, sensing, and communication applications.

The MAX687/MAX688/MAX689 family was engineered for high-accuracy, low-dropout regulation in battery-constrained systems, emphasizing external transistor flexibility, ultra-low shutdown current, and integrated power-fail monitoring for reliable system-level power control.

FAQ

What is the maximum output current supported by the MAX689EPA?

The MAX689EPA itself does not source output current-it drives an external PNP transistor. With a high-gain PNP like the FZT749 (β > 100), the MAX689EPA can support >1A output current. Base current is limited to ≥10mA, so I_LOAD(MAX) ≈ 10mA × β_MIN. For example, using FZT749 (β_MIN = 100), MAX689EPA enables up to 1A output. Actual capability depends on transistor selection, thermal design, and dropout margin.

Does the MAX689EPA have automatic latched shutdown like the MAX687?

No, the MAX689EPA does not feature automatic latched shutdown. Unlike the MAX687, which shuts down when V_OUT falls below 2.96V and remains latched off until the ON pin is pulsed, the MAX689EPA uses an active-low SHDN pin for external control. It enters standby (<25µA) at V_SHDN < 1.2V and full shutdown (<1µA) at V_SHDN < 0.2V, with no internal latch or auto-shutdown function.

What is the function of the BLIM pin on the MAX689EPA?

The BLIM pin on the MAX689EPA forms a current-sense node with the BASE pin to limit external PNP base drive. A resistor (RB) connected between BASE and BLIM sets maximum base current as I_BASE ≤ 0.1V / (RB + 5Ω). This prevents excessive quiescent current during dropout and provides soft current limiting without adding collector-side sense resistors-preserving low dropout performance while protecting the pass transistor.

Can the MAX689EPA be used with a 2.5V input supply?

No, the MAX689EPA requires a minimum input voltage of 2.7V to regulate its 3.0V output. At 2.5V input, the device cannot sustain regulation-dropout would exceed specification, and V_OUT would fall below 3.0V. For 2.5V–3.0V inputs, consider regulators with lower dropout (e.g., <100mV) or adjustable versions with external feedback. The MAX689EPA's 40mV dropout at 200mA assumes sufficient headroom (e.g., 3.04V min input at 200mA load).

Is the PFO output on the MAX689EPA push-pull or open-drain?

The PFO output on the MAX689EPA is open-drain. Unlike the MAX687 (which sources and sinks), MAX689EPA's PFO only sinks current when asserted low. An external pull-up resistor (to V_CC or another logic rail) is required to generate a valid high-level signal. This allows flexible voltage-level translation and wired-OR fault-bus configurations in multi-rail systems.