Analog Devices Inc./Maxim Integrated MAX687CSA

Overview

MAX687CSA from Maxim Integrated is a precision 3.3V fixed-output, low-dropout linear regulator requiring an external PNP pass transistor; it delivers up to 1A output current with 10mA minimum base drive, features automatic latched shutdown at 2.96V output, and includes power-fail monitoring (PFO) for battery protection in portable telephones and memory backup supplies.

For engineers reviewing the MAX687CSA datasheet, MAX687CSA pinout, MAX687CSA application, or MAX687CSA equivalent, this page provides verified technical context, real-world dropout behavior (40mV at 200mA), confirmed shutdown hysteresis (70mV), package-specific thermal limits (330mW µMAX), and validated alternative options for 3.3V low-power shutdown regulators.

Technical Context

The MAX687CSA implements a precision bandgap reference and dual comparator architecture: one monitors VOUT against 2.96V for latched shutdown, another triggers PFO at 170mV below nominal (3.13V). Its ON input requires a pulse high to initiate startup and must remain asserted until VOUT exceeds the shutdown threshold.

Base-current limiting is achieved via a 5Ω internal resistor and external RB between BASE and BLIM, enabling programmable IBASE ≤ 0.1V/(RB + 5Ω); compensation is handled by a non-polarized capacitor (10nF–100nF) on CC, directly stabilizing loop response without external op-amp feedback.

Key Specifications

Pinout & Package

MAX687CSA is housed in an 8-pin SO (Small Outline) package, measuring 4.9mm × 6.0mm × 1.75mm, rated for 0°C to +70°C operation and 471mW maximum power dissipation at +70°C (derating 5.88mW/°C above).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar 3.3V low-dropout regulator applications.

Compared with MAX687CSA, MAX688CSA offers identical regulation but removes autonomous shutdown - trading battery protection for flexible control. LT1528CS8 integrates the pass element but loses PFO and doubles shutdown current, making it unsuitable for long-term memory backup.

Availability

MAX687CSA is available at Aetrix Electronics and suitable for portable telephones, battery-powered memory backup systems, and portable instrumentation requiring stable component supply with guaranteed 0°C to +70°C operation and SO-package compatibility.

Supply support for MAX687CSA 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 interface applications, with emphasis on high-reliability industrial and portable systems.

The MAX687CSA belongs to Maxim's high-accuracy linear regulator product line, engineered specifically for battery-critical applications demanding autonomous shutdown, low dropout, and integrated power-fail signaling.

FAQ

What is the exact shutdown behavior of the MAX687CSA?

The MAX687CSA enters latched shutdown when its regulated output falls to 2.96V, disabling base drive to the external PNP transistor. Once latched off, the MAX687CSA remains disabled until the ON pin receives a new high pulse - preventing accidental re-enabling during brownout conditions and protecting batteries from over-discharge.

Does the MAX687CSA require an external PNP transistor, and why?

Yes, the MAX687CSA requires an external PNP pass transistor (e.g., FZT749) because it functions as a controller IC - providing precision reference, comparators, and base drive, but relying on the external transistor to handle high current and power dissipation. This architecture enables scalable output current beyond 1A while maintaining low dropout.

What is the role of the CC pin on the MAX687CSA, and what capacitor value is recommended?

The CC pin on the MAX687CSA connects to a non-polarized compensation capacitor (10nF typical, up to 100nF) to stabilize the control loop and prevent oscillation. Ceramic or polyester capacitors are required - aluminum/tantalum types are prohibited due to leakage current that shifts output voltage and PFO thresholds.

How does the PFO output function on the MAX687CSA, and how is it different from MAX688/MAX689?

The MAX687CSA PFO is a push-pull output that both sources and sinks current, tripping low when VOUT drops to 3.13V (170mV below nominal). In contrast, MAX688CSA and MAX689 variants use open-drain PFO outputs that only sink current - a key distinction confirmed in the Pin Description section of the datasheet.

Can the MAX687CSA operate with input voltages below 3.3V?

No - the MAX687CSA requires a minimum input voltage of 2.7V, but regulation is only maintained when VIN exceeds VOUT plus dropout voltage (e.g., ≥3.34V at 200mA). Below that, output collapses; the internal reference and comparators remain functional down to 2.7V, but regulation ceases.