Analog Devices Inc. LT1374IS8-5#PBF

Overview

LT1374IS8-5#PBF from Analog Devices (formerly Linear Technology) is a fixed 5V, 4.5A monolithic buck switching regulator in SO-8 package, featuring constant 500kHz current-mode operation, 0.07Ω internal NPN switch on-resistance, 2.5mA operating supply current, and cycle-by-cycle current limiting - deployed in battery-powered systems requiring compact, high-efficiency DC/DC conversion.

For engineers reviewing the LT1374IS8-5#PBF datasheet, LT1374IS8-5#PBF pinout, LT1374IS8-5#PBF application, or LT1374IS8-5#PBF equivalent, key selection considerations include its fixed 5V output, -40°C to 125°C industrial temperature rating, SO-8 thermal performance (θ_JA = 80°C/W with fused ground), shutdown capability (20µA I_Q), and compatibility with standard surface-mount magnetics and capacitors.

Technical Context

The LT1374IS8-5#PBF implements a current-mode, constant-frequency buck topology using an integrated bipolar NPN power switch driven via BOOST pin voltage boosting to achieve saturation and low conduction loss. Its error amplifier (2000 µMho transconductance) controls peak switch current through the VC pin, while internal slope compensation prevents subharmonic oscillation up to 90% duty cycle.

It features dual shutdown thresholds: 2.38V for undervoltage lockout (UVLO) and 0.4V for full micropower shutdown, plus FB/SENSE pin functionality tied directly to the 5V output for regulation and foldback protection. The SO-8 package uses fused ground (FGND) for improved thermal dissipation and EMI control.

Key Specifications

Pinout & Package

LT1374IS8-5#PBF is housed in an 8-lead plastic SO (SO-8) package with fused ground (FGND) pin for enhanced thermal performance. The package supports standard reflow soldering and requires PCB copper area under FGND for optimal thermal management (θ_JA = 80°C/W).

Key Features

Applications

Equivalent & Alternatives

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

Compared with LT1374CS8-5#PBF, the LT1374IS8-5#PBF provides guaranteed –40°C startup and extended thermal margin; compared with LT3502AIS8-5#PBF, it delivers 50% higher current at lower frequency, simplifying EMI filtering and enabling use of lower-cost magnetics.

Availability

LT1374IS8-5#PBF is available at Aetrix Electronics and suitable for battery-powered portable systems, distributed power rails, battery chargers, and embedded computing modules requiring stable component supply with industrial temperature assurance and long-term production continuity.

Supply support for LT1374IS8-5#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 LT product family, including precision analog, power management, and signal conditioning ICs.

The LT1374 series was designed specifically for high-current, high-efficiency buck conversion in space- and thermally constrained industrial and portable applications - emphasizing integration, ruggedness, and ease of use with standard passives.

FAQ

What is the maximum continuous output current of the LT1374IS8-5#PBF?

The LT1374IS8-5#PBF delivers up to 4.5 A continuously at duty cycles ≤50% (e.g., V_OUT = 5 V, V_IN ≥ 10 V). At higher duty cycles - such as V_IN = 8 V (DC = 62.5%) - peak switch current derates to ~4.3 A per the nonlinear formula in the datasheet. Thermal design must ensure junction temperature remains ≤125°C under worst-case load and ambient conditions.

Does the LT1374IS8-5#PBF require an external BOOST capacitor?

Yes, the LT1374IS8-5#PBF requires an external BOOST capacitor (typically 10 nF ceramic) and catch diode (e.g., CMDSH3) connected between BOOST and VSW pins. This network generates a voltage ~5 V above VIN to fully saturate the internal NPN switch - reducing conduction loss and enabling >89% efficiency. Omitting it results in excessive V_CE(sat) and thermal failure.

Can the LT1374IS8-5#PBF be synchronized to an external clock?

Yes, the LT1374IS8-5#PBF supports synchronization via its SYNC/SHDN pin. When configured as SYNC (not pulled low), it accepts logic-level signals from 580 kHz to 1 MHz with 10–90% duty cycle. The internal oscillator locks to the external frequency - useful for EMI reduction or phase alignment in multi-rail systems. No external components are needed beyond proper pull-up/pull-down resistors.

What is the purpose of the FGND pin on the LT1374IS8-5#PBF SO-8 package?

The FGND (fused ground) pin on the LT1374IS8-5#PBF is a dedicated, low-inductance ground connection designed to be soldered directly to a large PCB copper pour or internal ground plane. It reduces thermal resistance (θ_JA = 80°C/W vs. >100°C/W without it) and minimizes ground bounce during high dI/dt switching events - critical for stability and EMI control in high-current buck applications.

How does the LT1374IS8-5#PBF protect against short-circuit conditions?

The LT1374IS8-5#PBF employs three-tiered short-circuit protection: (1) cycle-by-cycle current limiting caps peak switch current at ~4.5 A; (2) SENSE pin foldback reduces switching frequency and current limit when output voltage collapses below 1.7 V; and (3) thermal shutdown disables operation if junction temperature exceeds 125°C. These functions operate simultaneously without external components.