Analog Devices Inc./Maxim Integrated MAX921CSA

Overview

The MAX921CSA 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 where precision, low power, and self-contained reference are critical.

For engineers reviewing the MAX921CSA datasheet, MAX921CSA pinout, MAX921CSA application, or MAX921CSA equivalent, key selection considerations include its guaranteed 1.3V below V+ common-mode input range, 12μs propagation delay at 10mV overdrive, internal reference accuracy, HYST pin hysteresis programming method, and SO-8 package compatibility with standard PCB footprints.

Technical Context

The MAX921CSA integrates a micropower comparator core with a precision 1.182V bandgap reference referenced to V−, not GND-requiring correct grounding for single-supply operation. Its unique output stage eliminates crowbar current during transitions, minimizing supply-induced parasitic feedback and enabling stable operation without stringent layout constraints.

Input voltage range extends from V− to (V+ − 1.3V), supporting true rail-to-rail sensing in low-voltage systems; hysteresis is implemented externally using two resistors between REF and HYST pins, enabling adjustable thresholds without feedback networks or complex calculations-specifically optimized for single-comparator configurations like auto-off power switches and level gauges.

Key Specifications

Pinout & Package

MAX921CSA is housed in an 8-pin SO (Small Outline) package, pin-compatible with industry-standard SOIC-8 footprints and reflow soldering profiles.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TLV3701IDBVR and LMV7235M5X, the MAX921CSA uniquely combines sub-4μA quiescent current, integrated ±1% reference, programmable hysteresis, and 40mA output drive-making it the only single-component solution for self-contained, low-power threshold detection in space-constrained designs.

Availability

MAX921CSA is available at Aetrix Electronics and suitable for battery-powered systems, threshold detectors, and oscillator circuits requiring stable component supply, long-term obsolescence management, and consistent SO-8 packaging across production batches.

Supply support for MAX921CSA 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 MAX921CSA belongs to the MAX921–MAX924 micropower comparator family, designed specifically for ultra-low-power, single-supply sensing applications where integration of reference, hysteresis, and robust output drive reduces system complexity and improves reliability.

FAQ

What is the maximum supply voltage for MAX921CSA in single-supply operation?

The MAX921CSA supports a single-supply voltage range of +2.5V to +11V. When operated from a single supply, V− must be connected to GND, and the absolute maximum rating for V+ to GND is +12V. Exceeding +11V may degrade reference accuracy or increase quiescent current beyond specification limits, so +11V is the recommended maximum operating voltage for reliable performance across the 0°C to +70°C range.

Can MAX921CSA operate from a dual supply, and how is the reference affected?

Yes, MAX921CSA supports dual-supply operation from ±1.25V to ±5.5V. In this configuration, the internal 1.182V reference remains referenced to V−, not GND-so REF = V− + 1.182V. This means the reference voltage shifts with the negative rail, preserving accurate differential thresholding. For example, with V+ = +5V and V− = −5V, REF = −3.818V, enabling bipolar threshold detection relative to the negative rail.

How is hysteresis programmed on MAX921CSA, and what is the maximum achievable band?

Hysteresis on MAX921CSA is programmed using the HYST pin: connect R1 between REF and HYST, and R2 between HYST and V−. The hysteresis band (VHB) ≈ 2 × (VREF − VHYST). Since VHYST can range from VREF down to (VREF − 50mV), the maximum VHB is 100mV. This method avoids positive-feedback instability and draws negligible current (<0.02nA), making it ideal for precision, low-power threshold applications.

Does MAX921CSA require power-supply bypass capacitors?

Power-supply bypass capacitors are not strictly required for MAX921CSA due to its crowbar-free output architecture and low supply current, provided the supply impedance is low and PCB traces are short. However, a 100nF ceramic capacitor placed close to the V+ and GND pins is recommended when supply leads are long or source impedance is high-especially in battery-powered systems with switching regulators-to suppress high-frequency noise coupling into the reference or inputs.

What is the guaranteed input common-mode voltage range for MAX921CSA?

The guaranteed input common-mode voltage range for MAX921CSA is from V− to (V+ − 1.3V) across the full 0°C to +70°C temperature range. This allows the IN+ and IN− pins to accept signals within 1.3V of the positive rail-critical for high-side sensing in 3.3V or 5V systems. Inputs may tolerate brief excursions up to 300mV beyond the rails without damage, but guaranteed operation is bounded by the specified range.