Analog Devices Inc./Maxim Integrated MAX921CSA+T

Overview

The MAX921CSA+T 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 temperature, and is widely used in battery-powered threshold detection circuits.

For engineers reviewing the MAX921CSA+T datasheet, MAX921CSA+T pinout, MAX921CSA+T application, or MAX921CSA+T equivalent, key selection criteria include its micropower operation at 3V/5V systems, internal reference accuracy, hysteresis configurability without external feedback, and robust output drive for direct LED or logic interfacing - all in an industry-standard 8-pin SO package.

Technical Context

The MAX921CSA+T implements a micropower comparator core paired with a precision 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 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–50mV to REF), enabling simple two-resistor programming with no external op-amp or feedback network required.

Key Specifications

Pinout & Package

MAX921CSA+T is housed in an 8-pin SO (Small Outline) package, pin-compatible with industry-standard 8-pin SOIC footprint (JEDEC MS-012). Thermal performance: 471mW max continuous power dissipation at TA = +70°C, derating 5.88mW/°C above.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LM393DR and TLV3691IDBVR, the MAX921CSA+T uniquely combines micropower operation, integrated ±1% reference, and 40mA push-pull output - making it optimal for self-contained, battery-powered threshold detectors where component count, layout simplicity, and long service life are critical.

Availability

MAX921CSA+T is available at Aetrix Electronics and suitable for battery-powered systems, threshold detectors, and oscillator circuits requiring stable component supply with guaranteed long-term availability and traceable sourcing.

Supply support for MAX921CSA+T 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, mixed-signal, and power management ICs for industrial, medical, communications, and consumer applications.

The MAX921CSA+T belongs to the MAX921–MAX924 micropower comparator family, engineered specifically for ultra-low-power, single-supply sensing in portable and energy-harvesting systems where reference integration, hysteresis simplicity, and robust output drive are essential.

FAQ

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

The MAX921CSA+T supports a single-supply voltage range of +2.5V to +11V. At +11V, the device remains fully specified for all parameters including input common-mode range (V− to V+ − 1.3V), output swing, and quiescent current (≤4μA). Exceeding +11V violates Absolute Maximum Ratings and may cause permanent damage.

Can MAX921CSA+T operate from a 3V battery without external components?

Yes. The MAX921CSA+T operates down to +2.5V and draws only ≤4μA quiescent current at 3V, making it ideal for direct connection to primary or rechargeable 3V batteries. Its integrated 1.182V reference and HYST pin allow complete threshold detection functionality - including hysteresis - using just two external resistors, with no additional ICs required.

How is hysteresis configured on MAX921CSA+T, and what is the maximum hysteresis band?

Hysteresis on MAX921CSA+T is configured by connecting two resistors between REF, HYST, and V−. The HYST pin accepts voltages from (REF − 50mV) to REF, producing a hysteresis band (VHB) ≈ 2 × (REF − VHYST). With the full 50mV offset, MAX921CSA+T achieves up to 100mV hysteresis band - sufficient to suppress noise-induced chatter in most low-frequency sensing applications.

Does MAX921CSA+T require a ground pin when used in dual-supply mode?

No. In dual-supply mode (e.g., ±5V), MAX921CSA+T uses V+ and V− pins only; Pin 1 (GND) is internally disconnected and must be left unconnected or tied to V−. The output swings from V+ to V−, and the internal reference is referenced to V− - not to a system ground - ensuring correct operation with split supplies.

What is the output behavior of MAX921CSA+T when driving a capacitive load?

The MAX921CSA+T output remains stable with capacitive loads up to 100pF, exhibiting 12μs propagation delay at 10mV overdrive. For larger loads (>100pF), response time increases linearly (e.g., ~16μs at 1nF), but no oscillation or ringing occurs due to its crowbar-free output architecture. No series resistance or isolation is required for typical PCB trace capacitance.