Analog Devices Inc. LT1424IN8-5#PBF

Overview

LT1424IN8-5#PBF from Analog Devices (formerly Linear Technology) is an industrial-grade monolithic isolated flyback switching regulator IC with fixed 5V output, integrated 1.6A switch, 285kHz oscillator, and primary-side sensing-eliminating need for optoisolators or third-winding feedback. It delivers up to 400mA at 5V from 3V–20V input in 8-pin PDIP package, targeting compact isolated DC/DC supplies in instrumentation and industrial automation.

For engineers reviewing the LT1424IN8-5#PBF datasheet, LT1424IN8-5#PBF pinout, LT1424IN8-5#PBF application, or LT1424IN8-5#PBF equivalent, key selection considerations include its primary-side regulation architecture, load-compensated 5V output accuracy, shutdown current of 20µA, 1.6A internal switch current limit, and compatibility with standard 1:1 transformers without auxiliary windings.

Technical Context

The LT1424IN8-5#PBF implements a current-mode control architecture with a dedicated flyback error amplifier that samples the primary-side flyback pulse waveform to infer isolated output voltage-enabling regulation without optocouplers or extra transformer windings. Its collapse-detect timing logic and minimum enable time (180ns) sustain regulation into discontinuous conduction mode.

It integrates a 35V/1.6A NPN power switch, 2.6V internal bias regulator, and programmable load compensation via external RCCOMP capacitor. The VC pin serves as both feedback amplifier output and current comparator input, with internal transconductance of 400–1600 µmho and reference voltage of 5.30V (±0.07V) at VSW.

Key Specifications

Pinout & Package

LT1424IN8-5#PBF is housed in an 8-lead plastic DIP (N8) package with 0.300-inch width, rated for –40°C to +125°C industrial temperature range and θ_JA = 130°C/W.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LT1424IS8-5, the LT1424IN8-5#PBF offers superior thermal margin in high-ambient environments due to PDIP's higher θ_JA, while LT3748HMSE-5#PBF trades integration for flexibility-requiring external FET but enabling 100V input and active clamp efficiency gains.

Availability

LT1424IN8-5#PBF is available at Aetrix Electronics and suitable for industrial sensor isolation, isolated communication interfaces, and medical instrumentation requiring stable component supply with guaranteed long-term manufacturability.

Supply support for LT1424IN8-5#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, Inc. (acquired Linear Technology in 2017) is a global leader in high-performance analog, mixed-signal, and power management semiconductors.

The LT1424 family was designed specifically for cost-sensitive, space-constrained isolated flyback power supplies-delivering regulated 5V or –9V outputs using off-the-shelf 1:1 transformers and eliminating optoisolators.

FAQ

What is the operating temperature range for the LT1424IN8-5#PBF?

The LT1424IN8-5#PBF is specified for industrial temperature operation from –40°C to +125°C junction temperature. Its N8 (PDIP) package has a thermal resistance θ_JA of 130°C/W, making it suitable for high-ambient environments when properly heatsinked or mounted on adequate copper area. This rating is confirmed in the Absolute Maximum Ratings table and applies across all electrical specifications marked with "G".

Does the LT1424IN8-5#PBF require an optoisolator or third-winding transformer?

No, the LT1424IN8-5#PBF does not require an optoisolator or third-winding transformer. It achieves isolated output regulation by directly sensing the primary-side flyback pulse waveform-deriving output voltage information without secondary-side feedback components. This architecture is explicitly stated in the product description, features list, and block diagram of the LT1424IN8-5#PBF datasheet.

What is the maximum output current capability of the LT1424IN8-5#PBF?

The LT1424IN8-5#PBF can deliver up to 400mA at 5V output using its integrated 1.6A NPN switch and standard 1:1 transformer. This value is specified in the "Typical Application" section and confirmed by the switch current limit (1.6A typical) and thermal limits of the N8 package. Output current is load- and transformer-dependent, but 400mA represents the validated design point for continuous operation at 25°C ambient.

How does load compensation work on the LT1424IN8-5#PBF?

Load compensation on the LT1424IN8-5#PBF corrects output voltage droop caused by secondary-side impedance (diode VF, transformer leakage, capacitor ESR). It uses the internal ROCOMP resistor and external RCCOMP capacitor (typically 0.1µF) to generate a current proportional to average switch current, which is subtracted from the feedback node-effectively raising the target output voltage under heavier loads. This mechanism is detailed in the "Load Compensation Theory" section of the LT1424IN8-5#PBF datasheet.

Can the LT1424IN8-5#PBF be synchronized to an external clock?

Yes, the LT1424IN8-5#PBF supports external synchronization via its SYNC pin (Pin 3). It accepts logic-level signals with 10–90% duty cycle and locks its internal 285kHz oscillator to external frequencies between 330kHz and 450kHz. Synchronization eliminates beat frequencies in multi-rail systems and aids EMI compliance-functionality verified in the Electrical Characteristics table under "SYNC Function" parameters.