Analog Devices Inc./Maxim Integrated MAX921CPA+

Overview

The MAX921CPA+ 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 0°C to +70°C, and is widely used in battery-powered threshold detection circuits.

For engineers reviewing the MAX921CPA+ datasheet, MAX921CPA+ pinout, MAX921CPA+ application, or MAX921CPA+ equivalent, key selection considerations include its internal reference accuracy, hysteresis configurability without external feedback, 12μs propagation delay at 10mV overdrive, GND-referenced output swing (V+ to GND), and compatibility with 3V/5V systems requiring micropower operation.

Technical Context

The MAX921CPA+ integrates a precision 1.182V bandgap reference referenced to V−, not GND, enabling stable threshold generation in single- or dual-supply configurations. Its comparator input common-mode range extends from V− to (V+ − 1.3V), supporting rail-to-rail sensing in low-voltage systems.

The unique output stage eliminates crowbar current during logic transitions, minimizing supply-line parasitic feedback and ensuring stability without mandatory bypassing. Hysteresis is implemented via the HYST pin-accepting 0–50mV below REF-enabling simple two-resistor configuration for noise-immune threshold detection without external op-amp feedback loops.

Key Specifications

Pinout & Package

MAX921CPA+ uses an 8-pin plastic DIP package (0.300" width) with through-hole mounting and industry-standard pin spacing.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LM393DR and TLV3701CDR, the MAX921CPA+ delivers integrated reference and hysteresis control in a single package-reducing component count, layout area, and calibration effort-while maintaining micropower operation ideal for portable and energy-harvesting systems.

Availability

MAX921CPA+ is available at Aetrix Electronics and suitable for battery-powered systems, threshold detectors, and oscillator circuits requiring stable component supply across commercial temperature range (0°C to +70°C).

Supply support for MAX921CPA+ 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 consumer systems.

The MAX921CPA+ belongs to the MAX921–MAX924 micropower comparator family, engineered specifically for ultra-low-quiescent-current threshold detection in space- and energy-constrained applications such as portable instrumentation and remote sensors.

FAQ

What is the maximum supply voltage for MAX921CPA+ in single-supply operation?

The MAX921CPA+ supports a single-supply voltage range of +2.5V to +11V. At +11V, it remains fully specified for all parameters including input common-mode range (V− to V+ − 1.3V), output swing (V+ to GND), and reference stability. Exceeding +11V risks permanent damage per Absolute Maximum Ratings.

Can MAX921CPA+ operate from a dual supply, and how is V− used?

Yes, MAX921CPA+ operates from dual supplies of ±1.25V to ±5.5V. In dual-supply mode, V− serves as the negative rail (e.g., −5V), GND remains unconnected, and the internal reference (REF) is referenced to V−-not GND-so REF = V− + 1.182V. The output swings from V+ to GND, not V−, preserving TTL compatibility.

How is hysteresis configured on MAX921CPA+, and what is the maximum hysteresis band?

Hysteresis on MAX921CPA+ is set by applying a voltage between REF − 50mV and REF to the HYST pin using two resistors. The hysteresis band (VHB) ≈ 2 × (REF − VHYST), yielding up to 100mV maximum. For example, connecting HYST to REF − 25mV gives ~50mV hysteresis-sufficient to suppress noise in typical battery-monitoring applications.

Does MAX921CPA+ require power-supply bypass capacitors?

MAX921CPA+ does not require bypass capacitors if the supply impedance is low and leads are short. However, a 100nF ceramic capacitor placed close to V+ and GND is recommended when supply impedance is high or PCB traces are long. Critically, the REF pin must never be bypassed-capacitive loading degrades reference stability and increases noise.

What is the output behavior of MAX921CPA+ when driving a capacitive load?

MAX921CPA+ maintains stability with capacitive loads up to 100nF, though propagation delay increases with load capacitance (e.g., ~14μs at 100nF vs. 12μs at 100pF). The output stage's crowbar-free design prevents oscillation, making it robust in noisy environments-even without careful layout-unlike many comparators requiring series resistance or isolation.