Analog Devices Inc./Maxim Integrated MAX689CSA+

Overview

MAX689CSA+ from Maxim Integrated is a precision 3.0V fixed-output, low-dropout linear regulator requiring an external PNP pass transistor; it delivers up to 1A output current with 40mV dropout at 200mA (FZT749), features active-low shutdown control (SHDN), power-fail monitoring (PFO), and operates from 2.7V to 11.0V input; used in battery-powered portable instruments and memory backup supplies.

For engineers reviewing the MAX689CSA+ datasheet, MAX689CSA+ pinout, MAX689CSA+ application, or MAX689CSA+ equivalent, this page provides verified technical context, real-world design meaning for key specs, validated pin functions, confirmed alternatives, and supply-chain support - all specific to the MAX689CSA+ SO-8 package variant.

Technical Context

The MAX689CSA+ implements a high-accuracy bandgap reference and precision voltage comparator to monitor output voltage against a 3.0V nominal setpoint, triggering PFO at −170mV deviation and enabling precise SHDN-controlled standby/shutdown transitions. Its base-drive architecture delivers ≥10mA sink capability to drive high-hFE PNP transistors like FZT749 without external current-sense circuitry.

Unlike the MAX687, the MAX689CSA+ lacks automatic latched shutdown and instead uses a three-level SHDN input: >1.25V = on, <1.2V = standby (<25µA I_IN), <0.2V = full shutdown (<1µA I_IN). PFO is open-drain and sinks current only - no sourcing capability - simplifying interface with microcontroller interrupt inputs.

Key Specifications

Pinout & Package

MAX689CSA+ is housed in an 8-pin SO (Small Outline) package per JEDEC MS-012, 150 mil body width, 1.27mm pitch. Pin 1 is marked by a beveled corner or dot; device orientation follows standard SO top-view labeling.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX688CSA+, the MAX689CSA+ provides lower output voltage for 3V systems and identical control architecture; versus LT1528CS8#PBF, it trades integration for superior light-load dropout and external transistor flexibility - essential for high-current, low-VIN applications.

Availability

MAX689CSA+ is available at Aetrix Electronics and suitable for portable instruments, battery-powered memory backup systems, and high-efficiency linear regulator designs requiring stable component supply across industrial temperature ranges and long production lifecycles.

Supply support for MAX689CSA+ 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, with emphasis on high reliability and performance in constrained environments.

The MAX687/MAX688/MAX689 product line was engineered specifically for battery-powered systems needing accurate, low-dropout regulation with programmable shutdown and power-fail warning - targeting portable telephony, instrumentation, and memory retention.

FAQ

What is the maximum output current supported by the MAX689CSA+?

The MAX689CSA+ itself does not deliver output current directly; it drives an external PNP transistor. With a high-gain device like the FZT749 (h_FE ≥ 100), the MAX689CSA+ can support >1A output. Using a pseudo-Darlington configuration (e.g., TIP42 + 2N4403), designs have achieved 4A output while maintaining low dropout. The actual limit depends on the selected PNP's h_FE, power dissipation rating, and heatsinking - not the MAX689CSA+ IC alone.

Does the MAX689CSA+ have automatic shutdown like the MAX687?

No, the MAX689CSA+ does not include automatic or latched shutdown. Unlike the MAX687, which shuts down when VOUT falls below 2.96V and remains latched off until ON is pulsed, the MAX689CSA+ relies solely on its active-low SHDN pin for output control. It offers three distinct states - on, standby (<25µA), and full shutdown (<1µA) - all user-initiated via SHDN voltage levels, with no internal voltage-triggered latch.

What is the function of the BLIM pin on the MAX689CSA+?

The BLIM pin on the MAX689CSA+ enables precise base-current limiting for the external PNP transistor. A resistor (RB) connected between BASE and BLIM sets the maximum base drive: I_BASE ≤ 0.1V / (RB + 5Ω). For example, RB = 12Ω limits base current to ~6mA. This protects against excessive quiescent current during dropout and provides output current limiting without adding series resistance in the PNP collector - preserving low dropout performance.

Can the MAX689CSA+ be used with ceramic output capacitors?

Yes, the MAX689CSA+ is compatible with ceramic output capacitors, provided they meet minimum capacitance and ESR requirements. The datasheet specifies a minimum C2 of 10µF for ≤100mA loads and recommends 1µF per 10mA for higher currents (e.g., 50µF for 500mA). ESR must be ≤1% of the load resistance - typically <100mΩ for common 500mA applications. X7R or X5R ceramics meeting these values ensure stable regulation and optimal transient response.

What is the purpose of the CC pin on the MAX689CSA+?

The CC pin on the MAX689CSA+ is the compensation node for the internal error amplifier. A non-polarized capacitor (10nF to 100nF, typically 10nF ceramic or polyester) must be connected from CC to GND. This capacitor stabilizes the control loop, prevents oscillation, and controls startup overshoot. Aluminum or tantalum electrolytics are prohibited due to leakage current (>25nA), which would shift output voltage and PFO thresholds. Proper CC placement is critical for consistent 3.0V accuracy and fast transient recovery.