Analog Devices Inc. LT1424CS8-5#TRPBF

Overview

LT1424CS8-5#TRPBF from Analog Devices (formerly Linear Technology) is a monolithic isolated flyback switching regulator IC designed for primary-side sensing of 5V isolated outputs without optoisolators or third-winding feedback. It integrates a 1.6A current-limited switch, 285kHz oscillator, load-compensated feedback amplifier, and shutdown control. Delivers up to 400mA at 5V using 1:1 transformers in industrial power supplies.

For engineers reviewing the LT1424CS8-5#TRPBF datasheet, LT1424CS8-5#TRPBF pinout, LT1424CS8-5#TRPBF application, or LT1424CS8-5#TRPBF equivalent, key selection criteria include primary-side regulation capability, 285kHz fixed-frequency operation, 7mA quiescent current, 5.30V internal reference, and SO-8 package compatibility with board-level isolation requirements.

Technical Context

The LT1424CS8-5#TRPBF implements a current-mode flyback controller with proprietary flyback error amplifier that samples the primary-side flyback pulse to infer secondary output voltage. Its collapse-detect timing logic enables stable regulation down to discontinuous conduction mode, supported by minimum enable time (180ns) and flyback enable delay (150ns).

Load compensation is achieved via external RCCOMP capacitor and internal ROCOMP resistor, enabling correction of output impedance errors caused by secondary ESR. The VC pin serves as both feedback amplifier output and current comparator input, with 1.9V internal clamp defining peak switch current limit.

Key Specifications

Pinout & Package

LT1424CS8-5#TRPBF is housed in an 8-lead plastic SOIC (SO-8) package with standard 1.27mm pitch, JEDEC MS-012AC compliant, thermal resistance θ_JA = 110°C/W.

Key Features

Applications

Equivalent & Alternatives

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

Compared with UCC28711DR and MAX17690ATP+, the LT1424CS8-5#TRPBF delivers superior load regulation (<±1%) and lower design complexity for fixed 5V isolated supplies, leveraging its unique load compensation and collapse-detect architecture - making it optimal for cost-sensitive, high-volume industrial power modules.

Availability

LT1424CS8-5#TRPBF is available at Aetrix Electronics and suitable for industrial automation, isolated communication interfaces, and medical instrumentation requiring stable component supply with guaranteed long-term availability and traceable sourcing.

Supply support for LT1424CS8-5#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, Inc. (including legacy Linear Technology products) is a global leader in high-performance analog, mixed-signal, and power management semiconductors, serving precision, industrial, automotive, and communications markets.

The LT1424 product line was developed specifically for cost-optimized, transformer-isolated 5V and –9V DC/DC conversion in space-constrained industrial and instrumentation systems - emphasizing primary-side regulation, minimal external components, and robust light-load performance.

FAQ

What is the primary function of the LT1424CS8-5#TRPBF in a power supply design?

The LT1424CS8-5#TRPBF functions as a primary-side sensing isolated flyback switching regulator IC that generates a tightly regulated 5V output without requiring an optoisolator or auxiliary transformer winding. It integrates all control, oscillator, protection, and power switch circuitry needed to implement a complete 400mA isolated DC/DC converter using only a 1:1 transformer and minimal external components. Its core innovation lies in deriving output voltage information directly from the primary-side flyback pulse waveform.

How does the LT1424CS8-5#TRPBF achieve regulation without an optoisolator?

The LT1424CS8-5#TRPBF achieves regulation without an optoisolator by sampling the amplitude and timing of the primary-side flyback pulse generated when the internal switch turns off. Its proprietary flyback error amplifier converts this pulse into a current proportional to the secondary output voltage, referenced to an internal 5.30V bandgap. This method eliminates optoisolator-related issues such as aging, temperature drift, and nonlinear transfer characteristics - a capability confirmed in the device's block diagram and timing analysis sections.

What is the role of the RCCOMP pin on the LT1424CS8-5#TRPBF?

The RCCOMP pin on the LT1424CS8-5#TRPBF connects to an external 0.1µF ceramic capacitor that forms part of the load compensation network. This network corrects for output voltage droop caused by secondary-side ESR (including rectifier forward drop and transformer leakage), improving load regulation from >±3% to <±1% across the 0–400mA range. The internal ROCOMP resistor and external capacitor work together to inject a compensating current into the feedback node - a feature explicitly detailed in the Applications Information section.

Can the LT1424CS8-5#TRPBF operate at very light loads?

Yes, the LT1424CS8-5#TRPBF maintains regulation down to approximately 1–2mA output current due to its collapse-detect circuitry and minimum flyback enable time of 180ns. Unlike conventional controllers that lose regulation in discontinuous conduction mode, the LT1424CS8-5#TRPBF uses dynamic timing control to sustain feedback validity even at extremely light loads - a capability verified in Typical Performance Characteristics curves G02 and G10, and confirmed in the Minimum Load Considerations section.

What package type is used for the LT1424CS8-5#TRPBF?

The LT1424CS8-5#TRPBF uses an 8-lead plastic SOIC (SO-8) package, also designated S8 in Linear Technology documentation. It conforms to JEDEC MS-012AC outline with 1.27mm lead pitch and thermal resistance θ_JA = 110°C/W. This package is distinct from the PDIP (N8) variant and is specified in the Package/Order Information table - with part marking "14245" laser-etched on the top surface.