Analog Devices Inc. LT1578IS8-2.5#TRPBF

Overview

LT1578IS8-2.5#TRPBF from Analog Devices (formerly Linear Technology) is a fixed-output 2.5V, 1.5A monolithic buck switching regulator in SO-8 package, featuring 200kHz constant-frequency current-mode control, 0.2Ω internal NPN switch, 4V–15V input range, and integrated feedback divider for precise 2.5V regulation. It targets portable computers and battery-powered systems requiring high efficiency at light loads.

For engineers reviewing the LT1578IS8-2.5#TRPBF datasheet, LT1578IS8-2.5#TRPBF pinout, LT1578IS8-2.5#TRPBF application, or LT1578IS8-2.5#TRPBF equivalent, key selection criteria include verified 2.5V fixed output accuracy (±2%), cycle-by-cycle current limiting (1.5A typ), low shutdown current (20µA), thermal resistance reduction via fused ground lead, and synchronizability up to 400kHz.

Technical Context

The LT1578IS8-2.5#TRPBF implements current-mode control with an internal 200kHz oscillator, slope-compensated peak-current sensing, and dual-loop regulation-error amplifier output (VC pin) sets switch current threshold while switch current is sensed across internal 0.2Ω on-resistance. Its BOOST pin enables saturation drive for the integrated NPN power switch, reducing conduction loss and enabling >88% efficiency at full load.

It features two-stage shutdown: 2.42V UVLO lockout and 0.4V deep micropower mode, plus FB/SENSE pin foldback protection that reduces switching frequency and current limit when output voltage collapses below 0.7V-critical for short-circuit survivability in battery systems. The SO-8 package includes a fused ground lead directly bonded to the die tab for θ_JA = 80°C/W.

Key Specifications

Pinout & Package

LT1578IS8-2.5#TRPBF uses an 8-lead plastic SOIC (SO-8) package with fused ground pin thermally and electrically connected to the internal tab for enhanced thermal dissipation and noise isolation.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LTC3605EDE-2.5#TRPBF and TPS54227DDAR, LT1578IS8-2.5#TRPBF delivers superior thermal performance (θ_JA = 80°C/W), deterministic foldback protection, and proven reliability in battery-backed systems-making it optimal where robustness, low I_Q, and thermal headroom outweigh raw efficiency or switching speed.

Availability

LT1578IS8-2.5#TRPBF is available at Aetrix Electronics and suitable for portable computers, battery-powered medical devices, and industrial distributed power systems requiring stable component supply, long-lifecycle support, and guaranteed parametric compliance over –40°C to 125°C.

Supply support for LT1578IS8-2.5#TRPBF 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) is a global leader in high-performance analog, mixed-signal, and power management semiconductors, serving precision instrumentation, industrial automation, and aerospace markets.

The LT1578 product line was designed specifically for noise-sensitive, battery-operated buck conversion applications-emphasizing low EMI, thermal resilience, and fault-tolerant operation in portable and embedded systems.

FAQ

What is the guaranteed output voltage accuracy of the LT1578IS8-2.5#TRPBF over temperature?

The LT1578IS8-2.5#TRPBF guarantees 2.5V output with ±2% tolerance over the full –40°C to 125°C junction temperature range. This is achieved via laser-trimmed internal feedback resistors and process-matched bandgap reference, confirmed in the Electrical Characteristics table under "Sense Voltage (Fixed 2.5)" with min/max values of 2.46V/2.54V at TJ = 25°C and 2.44V/2.56V over full temperature range.

Can the LT1578IS8-2.5#TRPBF be synchronized to an external clock, and what is its maximum sync frequency?

Yes, the LT1578IS8-2.5#TRPBF supports external synchronization via its SYNC pin (Pin 8). It accepts logic-level signals with 10–90% duty cycle and operates within a synchronizing range of 250kHz to 400kHz. The internal oscillator will lock to any frequency in this band-enabling EMI reduction through clock dithering or phase alignment with other converters in multi-rail systems.

How does the LT1578IS8-2.5#TRPBF protect itself during output short-circuit conditions?

The LT1578IS8-2.5#TRPBF employs dual-foldback protection triggered when the SENSE pin voltage falls below 0.7V: switching frequency reduces ~5:1 (to ~40kHz), and peak switch current limit folds back from 1.5A to <0.77A. This coordinated action limits power dissipation in both the IC and external components. The feature is inherent to the FB/SENSE pin function and requires no external circuitry.

What is the thermal resistance (θ_JA) of the LT1578IS8-2.5#TRPBF, and how is it achieved?

The LT1578IS8-2.5#TRPBF achieves θ_JA = 80°C/W via a fused ground lead directly bonded to the internal die tab in its SO-8 package. This design requires connection to a large PCB copper area (ground plane or thermal pad) to realize the specified thermal performance-unlike standard SO-8 packages, which typically exceed 120°C/W without such enhancement.

Does the LT1578IS8-2.5#TRPBF require an external boost capacitor, and what is its purpose?

Yes, the LT1578IS8-2.5#TRPBF requires an external boost capacitor (typically 10nF–100nF ceramic) between BOOST (Pin 3) and VIN (Pin 2). Its purpose is to generate a voltage higher than VIN to drive the base of the internal NPN power switch into saturation-reducing V_CE(sat) to ~0.3V and enabling >88% efficiency. Without it, the switch operates in linear region with excessive conduction loss.