Analog Devices Inc. LTC1440IS8#PBF

Overview

LTC1440IS8#PBF from Analog Devices (formerly Linear Technology) is an ultralow-power single comparator with integrated 1.182V ±1% voltage reference, programmable hysteresis via HYST pin, TTL/CMOS-compatible output capable of sourcing up to 40mA, and supply current of 4.4µA max over –40°C to +85°C. It operates from a single 2V–11V supply or dual ±1V–±5.5V supply and is used in battery-powered voltage monitoring and precision threshold detection.

For engineers reviewing the LTC1440IS8#PBF datasheet, LTC1440IS8#PBF pinout, LTC1440IS8#PBF application, or LTC1440IS8#PBF equivalent, key selection criteria include guaranteed input common-mode range (V– to V+ –1.3V), reference output stability with 0.01µF bypass capacitor, absence of crowbar current during output transitions, and compatibility with micropower system-level power budgeting.

Technical Context

The LTC1440IS8#PBF integrates a precision bandgap reference (1.182V ±1% over temperature) directly tied to the comparator's noninverting input path and accessible at REF pin. Its HYST pin enables external resistor-programmable hysteresis (up to 100mV total band), eliminating need for external feedback networks while maintaining sub-µA quiescent operation.

Unlike standard comparators, the LTC1440IS8#PBF features separate GND and V– pins-GND serves as comparator output return (enabling TTL-level swing from GND to V+), while V– sets the negative rail for internal circuitry. This architecture supports true single-supply operation with ground-referenced outputs and split-supply flexibility without level-shifting components.

Key Specifications

Pinout & Package

Package: 8-lead plastic SO (S8), 150°C junction rating, θ_JA = 175°C/W, JEDEC MS-012 variant.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX921ESA+ and LTC1540IDC#TRPBF, the LTC1440IS8#PBF uniquely combines programmable hysteresis, 40mA sourcing capability, and GND-referenced TTL output in an SO-8 package-making it optimal for space-constrained, self-contained threshold detectors requiring minimal external components and robust noise immunity.

Availability

LTC1440IS8#PBF is available at Aetrix Electronics and suitable for battery-powered system monitoring, ultralow-power threshold detection, and industrial sensor interface applications requiring stable component supply and long-term lifecycle support.

Supply support for LTC1440IS8#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 its precision analog product lines with full technical documentation and long-term manufacturing commitment.

The LTC1440IS8#PBF belongs to Linear's micropower comparator family designed specifically for energy-constrained applications including portable instrumentation, remote sensors, and always-on supervisory circuits where sub-µA quiescent current and integrated reference stability are mandatory.

FAQ

What is the maximum hysteresis voltage band achievable with LTC1440IS8#PBF?

The LTC1440IS8#PBF supports a maximum hysteresis voltage band of 100mV, derived from a 50mV differential between REF and HYST pins. This is achieved using two external resistors per Figure 4 in the datasheet. Exceeding 50mV on HYST risks violating absolute maximum ratings and may cause reference instability or inaccurate switching thresholds. The LTC1440IS8#PBF datasheet specifies this limit explicitly under "Hysteresis Input Voltage Range".

Can LTC1440IS8#PBF operate from a 1.8V supply?

The LTC1440IS8#PBF is specified for minimum 2V operation, and its input common-mode range extends only to V+ –1.3V. At 1.8V, the usable input range collapses to 0.5V - insufficient for reliable comparison against the 1.182V internal reference. While functional behavior may occur down to ~1.5V, performance degrades significantly: propagation delay increases, output drive weakens, and reference accuracy falls outside spec. For 1.8V systems, consider LTC1540IDC#TRPBF instead.

Does LTC1440IS8#PBF require an external bypass capacitor on the REF pin?

The LTC1440IS8#PBF reference output is designed to drive up to 0.01µF directly without oscillation, so a bypass capacitor is optional but strongly recommended for noise immunity. When used, a 0.01µF X7R ceramic capacitor placed close to REF and GND suppresses supply-induced transients that could cause false comparator trips. Larger capacitors require series damping resistors per Figure 2 in the datasheet; omitting bypassing increases susceptibility to V+ rail noise in shared-power systems.

How does the GND pin differ from V– on LTC1440IS8#PBF?

On the LTC1440IS8#PBF, GND (Pin 1) is the dedicated return path for the output stage, enabling TTL-compatible swing from 0V to V+. V– (Pin 2) is the negative supply rail for internal circuitry and comparator inputs. In single-supply operation, both connect to system ground; in dual-supply mode, V– connects to negative rail while GND remains at 0V. This separation avoids ground bounce from output switching and ensures clean logic-level outputs independent of V– potential.

Is LTC1440IS8#PBF pin-compatible with MAX921?

Yes - the LTC1440IS8#PBF is explicitly documented as a pin-compatible upgrade for MAX921/922/923 in the datasheet. Both share identical SO-8 pinout, supply voltage range, and basic comparator functionality. However, LTC1440IS8#PBF adds programmable hysteresis (HYST pin), higher output drive (40mA vs. 8mA), and lower supply current (4.4µA vs. 12µA). No PCB changes are required for drop-in replacement, though external hysteresis resistors may be omitted if not needed.