Analog Devices Inc./Maxim Integrated MAX981CSA

Overview

The MAX981CSA from Maxim Integrated is a single, ultra-low-power, open-drain comparator with integrated 1.182V ±2% voltage reference and programmable hysteresis via HYST pin. It operates from 2.5V to 11V single supply (or ±1.25V to ±5.5V dual supply), features 4µA max supply current over temperature, rail-to-rail input range down to V−, and separate GND pin for output stage-enabling bipolar-to-single-ended level translation in battery-powered threshold detection systems.

For engineers reviewing the MAX981CSA datasheet, MAX981CSA pinout, MAX981CSA application, or MAX981CSA equivalent, this page delivers verified technical context, exact pin functions, real-world use cases in low-voltage sensing, and validated alternative options for supply-constrained designs requiring stable reference and noise-immune comparison.

Technical Context

The MAX981CSA integrates a bandgap voltage reference referenced to V− (not GND) and a single comparator with open-drain N-channel MOSFET output sinking to GND. Its HYST pin enables user-programmable hysteresis using two external resistors-no feedback loop or complex equations required-and supports hysteresis bands up to 100mV.

Input common-mode range extends from V− to (V+ − 1.3V); absolute input voltage tolerance allows operation up to ±0.3V beyond rails. Output voltage swing reaches 11V above V−, supporting level-shifting even when V+ = V−, and propagation delay is 12µs (10mV overdrive, 100pF load, 1MΩ pullup).

Key Specifications

Pinout & Package

MAX981CSA is housed in an 8-pin SO (Small Outline) package with gull-wing leads, JEDEC MS-012AC compliant, 150-mil body width, and standard SOIC footprint.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX971CSA, the MAX981CSA trades ±1% reference accuracy for cost-sensitive applications where ±2% is sufficient; compared with TLV3701IDBVR, it delivers integrated reference and proven hysteresis simplicity at the cost of slightly higher quiescent current-ideal for fixed-threshold, battery-operated systems.

Availability

MAX981CSA is available at Aetrix Electronics and suitable for battery-powered systems, threshold detectors, and level translators requiring stable component supply, long-term lifecycle support, and guaranteed commercial-temperature performance (0°C to +70°C).

Supply support for MAX981CSA 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 MAX981CSA belongs to Maxim's ultra-low-power comparator family, engineered specifically for energy-constrained applications demanding integrated reference, programmable hysteresis, and rail-aware input operation without sacrificing speed or noise immunity.

FAQ

What is the reference voltage tolerance of the MAX981CSA over its operating temperature range?

The MAX981CSA features a 1.182V internal bandgap reference with ±2% accuracy over the commercial temperature range (0°C to +70°C). This specification is explicitly confirmed in the Electrical Characteristics table for MAX981–MAX984 devices under "C temp range" conditions. The reference is referenced to V−, not GND, and maintains this tolerance without external trimming or calibration. MAX981CSA users must account for this ±2% variation when designing resistor-divider networks for threshold setting.

Can the MAX981CSA operate from a 1.8V single supply?

No, the MAX981CSA is not specified or guaranteed to operate below 2.5V supply. The Absolute Maximum Ratings and Electrical Characteristics sections state a minimum supply voltage of 2.5V for reliable operation-including reference functionality and comparator performance. While some comparators in the broader MAX97x/MAX98x family (e.g., MAX974) may function down to 1V, the MAX981CSA datasheet explicitly restricts operation to ≥2.5V. Using 1.8V risks undefined behavior, reference dropout, and increased propagation delay.

How is hysteresis implemented on the MAX981CSA, and what is the maximum achievable hysteresis band?

Hysteresis on the MAX981CSA is implemented by connecting two resistors between REF, HYST, and V−-no external feedback or op-amps required. The HYST pin accepts voltages from (REF − 50mV) to REF, and the hysteresis band (V_HB) equals approximately twice the voltage difference between REF and HYST. With the maximum 50mV differential, MAX981CSA achieves up to 100mV hysteresis band. This method consumes negligible additional current and avoids stability issues associated with positive-feedback loops.

Does the MAX981CSA require a bypass capacitor on the REF pin?

No, the MAX981CSA datasheet explicitly states "Do not bypass the REF output." Bypassing REF can destabilize the internal bandgap circuit and increase noise. The reference is designed for direct connection to the HYST pin or external resistor dividers. If noise sensitivity is observed in system-level testing, layout improvements-such as short traces, ground shielding, and separation from noisy digital lines-are recommended instead of capacitive bypassing.

What is the purpose of the separate GND pin (Pin 1) on the MAX981CSA, and how does it differ from V− (Pin 2)?

The separate GND pin (Pin 1) on the MAX981CSA serves exclusively as the return path for the open-drain output transistor, while V− (Pin 2) is the negative supply terminal for the comparator core and reference. In single-supply operation, V− is tied to system GND-but Pin 1 remains the dedicated output sink node. This separation enables true level translation: for example, when V− = −5V (dual supply), the output still sinks to system GND (Pin 1), allowing clean 0V–5V logic output despite bipolar supplies. MAX981CSA leverages this architecture for bipolar-to-single-ended conversion without external components.