Analog Devices Inc./Maxim Integrated MAX921EPA

Overview

The MAX921EPA from Maxim Integrated is a single, ultra-low-power, rail-to-rail input comparator with integrated 1.182V ±1% bandgap reference, programmable hysteresis via HYST pin, and TTL/CMOS-compatible output capable of sourcing up to 40mA. It operates from +2.5V to +11V single supply (or ±1.25V to ±5.5V dual supply), features 4μA max quiescent current over –40°C to +85°C, and is used in battery-powered threshold detection circuits where precision, low power, and robust output drive are critical.

For engineers reviewing the MAX921EPA datasheet, MAX921EPA pinout, MAX921EPA application, or MAX921EPA equivalent, key selection considerations include its guaranteed –40°C to +85°C extended temperature operation, internal reference accuracy, hysteresis configurability without external feedback, and output swing from V+ to GND - all essential for reliable low-power sensing in portable instrumentation and industrial monitoring systems.

Technical Context

The MAX921EPA integrates a micropower comparator core with a precision 1.182V bandgap reference referenced to V−, not GND. Its unique output stage eliminates crowbar current during transitions, minimizing supply-line parasitic feedback and enabling stable operation without stringent PCB layout constraints.

Input common-mode range extends from V− to (V+ − 1.3V), supporting rail-to-rail sensing in single-supply configurations. Hysteresis is implemented via the HYST pin (REF − 0.05V to REF), allowing simple two-resistor configuration for noise-immune thresholding - a feature exclusive to MAX921/MAX923 within the family.

Key Specifications

Pinout & Package

MAX921EPA uses an 8-pin plastic DIP package with through-hole mounting, rated for –40°C to +85°C operation and compatible with standard wave-solder processes.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar comparator applications.

Compared with LM393DR and TLV3701CDR, the MAX921EPA uniquely combines internal ±1% reference, HYST-configurable hysteresis, and 40mA output drive in a single ultra-low-power package - making it irreplaceable in battery-powered threshold detectors demanding long life, precision, and direct actuation.

Availability

MAX921EPA is available at Aetrix Electronics and suitable for battery-powered systems, threshold detectors, and auto-off power switches requiring stable component supply across industrial temperature ranges and long production lifecycles.

Supply support for MAX921EPA 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, sensing, and interface applications in industrial, medical, and communications markets.

The MAX921EPA belongs to the MAX921–MAX924 micropower comparator family, engineered specifically for ultra-low-power, single-supply sensing applications where internal reference accuracy, hysteresis control, and robust output drive are mandatory.

FAQ

What is the operating temperature range of the MAX921EPA?

The MAX921EPA is specified for –40°C to +85°C operation, qualifying it for extended-temperature industrial and automotive cabin applications. This E-grade rating is confirmed in the Ordering Information table and Absolute Maximum Ratings section of the official datasheet. Unlike the C-grade (0°C to +70°C) versions, the MAX921EPA maintains its 4μA max supply current and ±1% reference accuracy across this full range - critical for outdoor or thermally uncontrolled deployments.

Does the MAX921EPA require external hysteresis components?

No - the MAX921EPA includes a dedicated HYST pin that enables configurable hysteresis using just two external resistors (REF to HYST and HYST to V−). This eliminates the need for external positive-feedback networks or op-amps. The HYST pin accepts 1.132V–1.182V, allowing a maximum hysteresis band of 100mV. When unused, HYST must be tied to REF. This architecture is intrinsic to the MAX921EPA and differs from alternatives like LM393DR that lack this feature entirely.

Can the MAX921EPA operate from a 3V supply?

Yes - the MAX921EPA operates from +2.5V to +11V single supply, fully supporting 3V systems. At V+ = 3V, its input common-mode range extends from V− (GND) to 1.7V, and propagation delay remains 14μs (typical) at 10mV overdrive. Supply current stays ≤4μA. This makes the MAX921EPA ideal for modern 3V microcontroller-based sensors, unlike older comparators with minimum 5V requirements.

What is the purpose of the REF pin on the MAX921EPA?

REF is the output of the internal 1.182V ±1% bandgap voltage reference, referenced to V− (not GND). It provides a stable, temperature-compensated threshold voltage for precision comparisons. The MAX921EPA's REF can source up to 25μA (at +25°C) and sink up to 15μA, enabling direct connection to resistor dividers for adjustable thresholds. Bypassing REF is prohibited - doing so degrades noise performance and may cause instability per the datasheet Layout Guidelines.

Is the MAX921EPA pin-compatible with other devices in the MAX92x family?

No - the MAX921EPA has a unique 8-pin DIP pinout optimized for single-comparator operation with REF, HYST, and GND pins. MAX922EPA (dual, no REF/HYST) and MAX923EPA (dual, with REF/HYST) share the same package footprint but differ in pin function mapping (e.g., pin 5 is IN− on MAX921EPA but INB− on MAX923EPA). Substituting without schematic and layout review will result in functional failure. Always verify pin functions using the "Pin Descriptions" table in the MAX921–MAX924 datasheet.