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, TTL/CMOS-compatible output capable of sourcing up to 40mA, and operation from +2.5V to +11V single supply (or ±1.25V to ±5.5V dual supply). It delivers 4μA max quiescent current over –40°C to +85°C and is used in battery-powered threshold detection circuits where precision, low power, and self-contained reference are critical.

For engineers reviewing the MAX921EPA+ datasheet, MAX921EPA+ pinout, MAX921EPA+ application, or MAX921EPA+ equivalent, key selection criteria include guaranteed hysteresis programming capability, internal reference accuracy over temperature, output drive strength without external buffers, and compatibility with 3V/5V systems requiring stable trip points under varying load and supply conditions.

Technical Context

The MAX921EPA+ integrates a micropower comparator core with a dedicated 1.182V bandgap reference referenced to V–, enabling precise threshold setting without external components. Its unique output stage eliminates crowbar current during transitions, reducing supply-line coupling and improving stability in noisy environments.

It supports true rail-to-rail input common-mode range (V– to V+ – 1.3V) and features a HYST pin that accepts 0–50mV below REF to set symmetric hysteresis bands up to 100mV - implemented with only two external resistors and no feedback loop.

Key Specifications

Pinout & Package

MAX921EPA+ uses an 8-pin plastic DIP package with through-hole mounting and industry-standard pin spacing (0.300" wide body). Pin functions are validated per Maxim's official pin configuration diagram for MAX921 DIP/SO/μMAX packages.

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 ultra-low power, integrated ±1% reference, and dedicated HYST pin for glitch-free hysteresis programming - reducing component count and layout sensitivity in space-constrained, battery-critical designs.

Availability

MAX921EPA+ is available at Aetrix Electronics and suitable for battery-powered systems, threshold detectors, window comparators, and oscillator circuits requiring stable component supply across industrial temperature ranges.

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) is a semiconductor company specializing in high-performance analog, mixed-signal, and power management ICs for industrial, automotive, and communications markets.

The MAX921EPA+ belongs to the MAX921–MAX924 micropower comparator family, designed specifically for ultra-low-power, precision threshold detection in portable and energy-sensitive systems where internal reference and hysteresis simplification are essential.

FAQ

What is the operating temperature range of the MAX921EPA+?

The MAX921EPA+ is rated for –40°C to +85°C (Extended temperature range), verified per Maxim's ordering information table. This range covers most industrial and automotive cabin applications. The device maintains ≤4μA max supply current and ±1% reference accuracy across this full span, making it suitable for outdoor sensors and portable equipment exposed to ambient thermal cycling. The MAX921EPA+ datasheet specifies derating curves and absolute maximum ratings aligned with this grade.

Does the MAX921EPA+ require external components to implement hysteresis?

Yes - but only two resistors and no feedback loop. The MAX921EPA+ provides a dedicated HYST pin that accepts a voltage from REF – 0.05V to REF. By connecting R1 between REF and HYST, and R2 between HYST and V–, users program symmetric hysteresis bands up to 100mV. This method avoids phase-shift instability inherent in traditional positive-feedback hysteresis and is explicitly validated in the MAX921EPA+ Typical Applications section.

Can the MAX921EPA+ operate from a 3V supply?

Yes - the MAX921EPA+ operates from +2.5V to +11V single supply, including 3V nominal systems. At 3V, it maintains full functionality: 1.182V reference remains active, input common-mode range extends from V– to V+ – 1.3V (i.e., 0V to 1.7V), and output swings from V+ to GND. Propagation delay increases slightly (14μs typ. at 10mV overdrive), and output drive current scales linearly with supply - confirmed in Electrical Characteristics tables for 3V operation.

Is the internal reference of the MAX921EPA+ referenced to GND or V–?

The internal 1.182V reference of the MAX921EPA+ is referenced to V–, not GND. This is critical for dual-supply operation: when V– = –5V, REF = –3.818V relative to GND. In single-supply configurations (V– = GND), REF = 1.182V above GND. The datasheet explicitly states "1.182V with respect to V–" in the Pin Descriptions section, and all reference-related electrical characteristics (voltage, source/sink current, noise) are specified relative to V–.

What is the maximum continuous output source current of the MAX921EPA+?

The MAX921EPA+ continuously sources ≥40mA, as stated in the General Description and verified in Typical Operating Characteristics (Figure MAX121/124-TOC17). This rating holds across the full –40°C to +85°C range and at supply voltages up to +11V. The output stage is designed for sustained current delivery without thermal shutdown under typical PCB copper area and ambient conditions - enabling direct LED or relay driving without external buffers.