Analog Devices Inc. LTC1440CS8#PBF

Overview

LTC1440CS8#PBF from Analog Devices (formerly Linear Technology) is an ultralow-power single comparator with integrated 1.182 V ±1% bandgap reference, programmable hysteresis via HYST pin, TTL/CMOS-compatible output capable of sourcing up to 40 mA, and operation from 2 V to 11 V single supply. It delivers 2.1 µA typical supply current at 25°C and supports battery-powered voltage monitoring, threshold detection, and micropower oscillator circuits.

For engineers reviewing the LTC1440CS8#PBF datasheet, LTC1440CS8#PBF pinout, LTC1440CS8#PBF application, or LTC1440CS8#PBF equivalent, key selection criteria include its guaranteed input common-mode range (V– to V+ – 1.3 V), reference output stability with 0.01 µF bypass capacitance, absence of crowbar current during output transitions, and compatibility with split-supply configurations when GND is tied to V–.

Technical Context

The LTC1440CS8#PBF integrates a precision 1.182 V reference referenced to V–, enabling direct use as a stable trip-point source without external components. Its comparator core features rail-to-rail input capability down to the negative supply and eliminates supply glitches by avoiding cross-conducting current during logic transitions.

Hysteresis is implemented externally via two resistors between REF, HYST, and V–, supporting programmable voltage bands up to 100 mV (±50 mV around REF). The output stage operates in push-pull CMOS mode, swinging from GND to V+, ensuring TTL compatibility and continuous 40 mA sourcing capability - critical for driving LEDs or small logic loads directly.

Key Specifications

Pinout & Package

Package: 8-lead plastic SO (S8), 3.9 mm × 4.9 mm × 1.5 mm, RoHS-compliant lead-free (PBF).

Key Features

Applications

Equivalent & Alternatives

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

Compared with LTC1440CS8#PBF, LTC1540IS8#PBF trades hysteresis flexibility for extreme current reduction, while LT6700-1IMS8#PBF offers broader supply tolerance and lower reference voltage at the cost of open-drain interface and reduced reference precision.

Availability

LTC1440CS8#PBF is available at Aetrix Electronics and suitable for battery-powered system monitoring, ultralow-power threshold detection, and micropower oscillator circuits requiring stable component supply across industrial, medical, and portable electronics programs.

Supply support for LTC1440CS8#PBF 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

Analog Devices acquired Linear Technology in 2017 and maintains full technical and manufacturing continuity for the LTC portfolio, including precision analog, power management, and signal conditioning ICs.

The LTC1440CS8#PBF belongs to Linear's micropower comparator family designed specifically for energy-constrained applications where long battery life, integrated reference stability, and glitch-free switching are mandatory - such as IoT edge nodes and portable instrumentation.

FAQ

What is the maximum hysteresis voltage achievable with LTC1440CS8#PBF?

The LTC1440CS8#PBF supports a maximum hysteresis voltage band of 100 mV, achieved when the voltage difference between REF and HYST pins reaches its limit of 50 mV. This is implemented using two external resistors: one from REF to HYST, and another from HYST to V–. The hysteresis band may vary up to ±15% due to resistor tolerances and temperature drift. Designers should verify actual thresholds using worst-case resistor values in simulation or bench testing before finalizing the LTC1440CS8#PBF circuit.

Can LTC1440CS8#PBF operate from a 1.8 V supply?

The LTC1440CS8#PBF is specified for minimum 2 V operation, but functional behavior has been observed down to 1.5 V in characterization. At 1.8 V, the internal 1.182 V reference remains active, though comparator propagation delay increases and output drive strength degrades. Input common-mode range shrinks to ~0.7 V below V+, potentially limiting valid input swing. For production designs, Analog Devices recommends staying within the 2 V to 11 V rated range; use LTC1540IS8#PBF instead for true sub-2 V operation with guaranteed specs.

Does LTC1440CS8#PBF require external bypass capacitors?

Yes - a 0.1 µF ceramic capacitor is recommended between V+ and GND (or V–) when the LTC1440CS8#PBF output sources more than 1 mA or when supply source impedance is high. Additionally, the REF pin can directly drive up to 0.01 µF without oscillation, but larger bypass caps (e.g., 10 µF) require a series damping resistor per Figure 2 in the datasheet. Omitting these capacitors risks reference instability, false comparator triggering, or increased propagation delay variation under dynamic load conditions.

Is LTC1440CS8#PBF pin-compatible with MAX921?

Yes - the LTC1440CS8#PBF is explicitly documented as a pin-compatible upgrade for MAX921 (and MAX922/MAX923) in Linear's datasheet. Pin mapping matches exactly: GND (1), V– (2), IN+ (3), IN– (4), HYST (5), REF (6), V+ (7), OUT (8). However, note that LTC1440CS8#PBF offers lower supply current (2.1 µA vs. 3.5 µA typ), tighter reference accuracy (±1% vs. ±2%), and higher output drive (40 mA vs. 8 mA), making it a functional and performance-enhancing drop-in replacement where layout reuse is critical.

What is the temperature coefficient of the reference in LTC1440CS8#PBF?

The LTC1440CS8#PBF reference exhibits a typical temperature coefficient of 50 ppm/°C over –40°C to 85°C, contributing to its ±1.5% total accuracy across temperature. This is derived from the 1.164 V to 1.200 V specification band at –40°C to 85°C, centered on the nominal 1.182 V. The coefficient is inherent to the bandgap design and is not adjustable. For applications requiring tighter thermal stability, consider post-regulation or calibration - but for most battery-monitoring and threshold-detection uses, this drift is negligible relative to system-level tolerances.