Analog Devices Inc./Maxim Integrated MAX689CSA+T

Overview

The MAX689CSA+T from Maxim Integrated is a precision 3.0V fixed-output, low-dropout linear regulator requiring an external PNP pass transistor (e.g., FZT749) to deliver up to 1A output current. It features active-low shutdown control (SHDN), open-drain power-fail output (PFO), ±2% output accuracy, and operates from 2.7V to 11.0V input. It is designed for battery-powered portable instruments and memory backup supplies where regulated 3.0V rail stability and controlled shutdown are critical.

For engineers reviewing the MAX689CSA+T datasheet, MAX689CSA+T pinout, MAX689CSA+T application, or MAX689CSA+T equivalent, key selection considerations include its 3.0V fixed output, SHDN-controlled standby/shutdown sequencing, PFO voltage monitoring threshold (2.83V nominal), dropout performance with external PNP selection, and SO-8 package compatibility with board-level thermal management requirements.

Technical Context

The MAX689CSA+T implements a precision bandgap reference and high-gain error amplifier to regulate 3.0V output using external PNP base drive via BASE and BLIM pins. Its SHDN input provides three-level operation: ON (>1.25V), standby (<1.2V, <25µA supply), and full shutdown (<0.2V, <1µA supply), enabling precise voltage-triggered disablement without latching.

PFO is an open-drain comparator output that asserts low when VOUT falls 170mV below nominal (i.e., at ~2.83V), with 7mV hysteresis. The device does not auto-shutdown on undervoltage - unlike MAX687 - making it suitable for externally managed power sequencing in systems where battery discharge protection is handled by host logic or dedicated fuel gauges.

Key Specifications

Pinout & Package

MAX689CSA+T is housed in an 8-pin SO (Small Outline) package, 3.9mm × 4.9mm body, 1.75mm height, with 1.27mm lead pitch. Thermal pad not present; standard SO thermal dissipation applies.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX688CSA+T, the MAX689CSA+T delivers identical control functionality at 3.0V - critical for 3.0V microcontrollers and low-voltage memory. Versus LT1129CS8-3.0, MAX689CSA+T supports higher output current and lower dropout via external PNP, but requires additional transistor and bias components.

Availability

MAX689CSA+T is available at Aetrix Electronics and suitable for portable medical sensors, industrial data loggers, memory backup supplies, and portable test equipment requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for MAX689CSA+T 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 U.S.-based semiconductor company specializing in high-performance analog, mixed-signal, and power management ICs for industrial, automotive, and communications markets.

The MAX687/MAX688/MAX689 family was designed specifically for high-accuracy, low-dropout regulation in battery-powered systems where external PNP flexibility enables scalable current delivery and ultra-low dropout - distinguishing it from monolithic LDOs.

FAQ

What is the output voltage tolerance of the MAX689CSA+T over temperature and load?

The MAX689CSA+T delivers a fixed 3.0V output with ±2% accuracy across the full operating temperature range (−40°C to +85°C) and load conditions (1µA to >1A with appropriate PNP). Electrical Characteristics table specifies min/max as 2.9V to 3.1V at TA = TMIN to TMAX, with typical distribution centered at 3.0V (±0.06V) per production testing data.

Does the MAX689CSA+T have automatic shutdown like the MAX687?

No, the MAX689CSA+T does not feature automatic latched shutdown on output undervoltage. Unlike the MAX687, which shuts down when VOUT falls below 2.96V and remains latched until ON is pulsed, the MAX689CSA+T relies solely on the SHDN pin for enable/disable control - providing externally managed sequencing without auto-latch behavior.

What external PNP transistor is recommended for use with the MAX689CSA+T?

The Zetex FZT749 is the recommended PNP transistor for the MAX689CSA+T, as validated in the datasheet's typical operating circuits and electrical characteristics. It provides sufficient hFE (>100), low V_CE(SAT), and thermal capability to support >1A output with minimal dropout. Other qualified options include 2N2907A and TIP42, depending on current and thermal requirements.

How does the PFO output behave during shutdown of the MAX689CSA+T?

During shutdown (SHDN < 0.2V), the PFO output of the MAX689CSA+T is forced low and sinks current regardless of the actual VOUT level. This behavior is explicitly defined in the Pin Description and Detailed Description sections - ensuring predictable fault signaling even when the regulator is disabled, supporting safe system-level power-down sequences.

What is the minimum output capacitance required for stable operation of the MAX689CSA+T?

The MAX689CSA+T requires a minimum output capacitance (C2) of 10µF for loads up to 100mA. For higher loads, the datasheet specifies 1µF per 10mA (e.g., 50µF for 500mA). Capacitor ESR must be ≤1% of load resistance; low-ESR types such as ceramic or OS-CON are recommended. Instability or excessive ripple may occur if C2 falls below these values or uses high-leakage electrolytics.