Analog Devices Inc./Maxim Integrated MAX688CUA

Overview

The MAX688CUA from Maxim Integrated is a 3.3V fixed-output, high-accuracy low-dropout linear regulator requiring an external PNP pass transistor. It delivers up to 1A output current with dropout as low as 40mV at 200mA (FZT749), features active-low shutdown control (SHDN), power-fail monitoring (PFO), and operates from 2.7V to 11.0V input. It is used in portable telephones and battery-powered instrumentation where precise voltage regulation and controlled shutdown are critical.

For engineers reviewing the MAX688CUA datasheet, MAX688CUA pinout, MAX688CUA application, or MAX688CUA equivalent, this page provides verified technical context, real-world design meaning of specifications, validated pin functions, confirmed alternative parts with functional distinctions, and supply-chain support details for industrial and OEM deployment.

Technical Context

The MAX688CUA implements precision regulation using an internal bandgap reference and error amplifier driving an external PNP transistor via the BASE pin. Its SHDN input enables three-level operation-on (>1.25V), standby (<1.2V, <25µA supply), and full shutdown (<0.2V, <1µA supply)-with ±2% threshold accuracy and 70mV hysteresis to prevent chatter.

Power-fail detection is performed by a dedicated comparator monitoring VOUT; PFO asserts low when output drops 170mV below nominal (3.3V), and remains open-drain during all operating modes. Base-current limiting is achieved via a resistor between BASE and BLIM, setting IBASE ≤ 0.1V/(RB + 5Ω) to constrain output current without compromising dropout performance.

Key Specifications

Pinout & Package

MAX688CUA is housed in an 8-pin µMAX package (2.1mm × 1.6mm, 0.5mm pitch), optimized for space-constrained portable designs. The package is RoHS-compliant and rated for 0°C to +70°C operation.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LT1528CS8#PBF and TPS76333DBVR, the MAX688CUA uniquely balances ultra-low I_Q, sub-50mV dropout at moderate loads, external transistor scalability to >4A, and integrated battery-protection logic - making it optimal for high-efficiency, high-flexibility portable power rails.

Availability

MAX688CUA is available at Aetrix Electronics and suitable for portable telephones, battery-powered instruments, and memory backup supplies requiring stable component supply across extended production lifecycles.

Supply support for MAX688CUA 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 and mixed-signal ICs for power, interface, and sensing applications.

The MAX687/MAX688/MAX689 family was designed specifically for battery-critical portable systems requiring precision low-dropout regulation with intelligent power-fail monitoring and scalable output current via external PNP transistors.

FAQ

What is the maximum output current supported by the MAX688CUA?

The MAX688CUA itself does not deliver output current directly-it drives an external PNP transistor. With a high-gain device like the FZT749 (β > 100), the MAX688CUA supports >1A output. Using a pseudo-Darlington configuration (e.g., TIP42 + 2N4403), the MAX688CUA can regulate up to 4A while maintaining low dropout. Output current is limited by base drive capability (≥10mA) and the external transistor's ratings.

Does the MAX688CUA have automatic shutdown like the MAX687?

No. Unlike the MAX687, the MAX688CUA does not feature automatic latched shutdown triggered by low output voltage. Instead, it uses the SHDN pin for explicit external control: pulling SHDN below 0.2V fully shuts down the device (<1µA I_Q), while levels between 0.2V and 1.2V place it in standby (<25µA). This gives designers full firmware or hardware control over power sequencing.

What is the function of the BLIM pin on the MAX688CUA?

The BLIM pin on the MAX688CUA serves as the sense node for base-current limiting. When a resistor (RB) is connected between BASE and BLIM, the internal comparator limits base current to IBASE ≤ 0.1V / (RB + 5Ω). This protects the external PNP during dropout and enables predictable output current limiting without adding a collector-sense resistor that would increase dropout voltage.

Can the MAX688CUA be used with ceramic output capacitors?

Yes, the MAX688CUA is compatible with ceramic output capacitors, provided they meet minimum capacitance (≥10µF for ≤100mA; ≥1µF per 10mA above that) and low ESR requirements (ESR ≤ 1% of load resistance). Ceramic caps are preferred for their stability and low ESR, but ensure DC bias derating is considered - e.g., a 22µF X7R 6.3V ceramic may drop to ~12µF at 3.3V bias.

What is the purpose of the CC pin on the MAX688CUA?

The CC pin on the MAX688CUA is the compensation node for the internal error amplifier. A 10nF non-polarized capacitor (e.g., ceramic or polyester) must be connected from CC to GND to stabilize the control loop. Values up to 100nF may be used to reduce startup overshoot, though larger values extend power-up time. Polarized capacitors (aluminum/tantalum) are unsuitable due to leakage current affecting output accuracy.