Analog Devices Inc. LT1424CN8-9#PBF

Overview

LT1424CN8-9#PBF from Analog Devices (formerly Linear Technology) is a monolithic isolated flyback switching regulator IC designed for PCMCIA Type II-compliant –9V supplies. It integrates a 1.6A switch, current-mode control, primary-side output voltage sensing, and load compensation. Delivers up to 200mA at –9V with no optoisolator or third winding required, operating from 3V–20V input.

For engineers reviewing the LT1424CN8-9#PBF datasheet, LT1424CN8-9#PBF pinout, LT1424CN8-9#PBF application, or LT1424CN8-9#PBF equivalent, key selection considerations include its fixed –9V output, 285kHz switching frequency, 8-pin PDIP package, discontinuous-mode regulation capability, and integrated load compensation for improved line/load regulation in isolated DC/DC designs.

Technical Context

The LT1424CN8-9#PBF implements a proprietary flyback error amplifier that samples the primary-side flyback pulse waveform to derive isolated output voltage information-eliminating need for optocouplers or auxiliary windings. Its collapse-detect timing logic enables stable regulation down to ~2–3mA load in discontinuous conduction mode.

It uses current-mode control with cycle-by-cycle peak current limiting (1.6A typical), internal 2.6V bias regulator, and externally programmable frequency synchronization (330–450kHz range). The VC pin serves as both feedback amplifier output and current comparator input, with external capacitor-based loop compensation.

Key Specifications

Pinout & Package

LT1424CN8-9#PBF is housed in an 8-lead plastic DIP (N8) package with 0.300-inch width, lead pitch of 0.100 inch, and JEDEC MS-001 compliant footprint. Thermal resistance θ_JA = 130°C/W.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LT1424CN8-9#PBF, LT1425CS8#PBF offers design flexibility at the cost of increased layout complexity and BOM count, while UCC28C43D necessitates optocoupler-based feedback and external switching, making it unsuitable for height-limited or maintenance-sensitive applications where LT1424CN8-9#PBF's integrated switch and primary-side sensing deliver superior reliability and compactness.

Availability

LT1424CN8-9#PBF is available at Aetrix Electronics and suitable for isolated DC/DC converters, PCMCIA power modules, and industrial Ethernet interface supplies requiring stable component supply, long-term lifecycle support, and commercial-grade temperature performance.

Supply support for LT1424CN8-9#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 LT1424CN8-9#PBF belongs to Linear's legacy isolated flyback controller family, engineered specifically for compact, optocoupler-free –9V supplies in portable and space-constrained networking equipment.

FAQ

What is the function of the RCCOMP pin on the LT1424CN8-9#PBF?

The RCCOMP pin on the LT1424CN8-9#PBF connects to an external capacitor that enables load compensation-correcting for output voltage droop caused by secondary-side ESR under varying load conditions. This feature improves load regulation to within ±1% across 0–200mA, critical for stable operation in isolated LAN supplies. The LT1424CN8-9#PBF uses this pin to subtract a current proportional to average switch current from the feedback node, dynamically adjusting the target output voltage.

Does the LT1424CN8-9#PBF require an optoisolator or third-winding transformer?

No, the LT1424CN8-9#PBF does not require an optoisolator or third-winding transformer. It achieves isolated output voltage regulation by sampling the primary-side flyback pulse waveform-a proprietary technique that eliminates both components while maintaining tight regulation. This architecture reduces bill-of-materials cost, board area, and height, making the LT1424CN8-9#PBF ideal for PCMCIA Type II applications with ≤2.41mm profile limits.

What is the minimum load required for regulation with the LT1424CN8-9#PBF?

The LT1424CN8-9#PBF maintains regulation down to approximately 2–3mA due to its collapse-detect timing logic and ability to operate deep into discontinuous conduction mode. In the reference PCMCIA application, a 1.8kΩ preload resistor ensures 5mA minimum load. Below ~2mA, output voltage rises as feedback sampling becomes unreliable-this behavior is documented in the LT1424CN8-9#PBF datasheet's Applications Information section.

Can the LT1424CN8-9#PBF be synchronized to an external clock?

Yes, the LT1424CN8-9#PBF supports external clock synchronization via the SYNC pin (Pin 3), accepting TTL/CMOS-compatible square waves with 10–90% duty cycle. The internal oscillator locks to input frequencies between 330kHz and 450kHz, enabling EMI reduction through frequency dithering or alignment with system clocks. When unused, the SYNC pin must be tied to ground-floating is not permitted per the LT1424CN8-9#PBF datasheet.

What package type is used for the LT1424CN8-9#PBF?

The LT1424CN8-9#PBF uses an 8-lead plastic DIP (PDIP) package designated N8, with 0.300-inch body width and JEDEC MS-001 outline. It features 0.100-inch lead pitch, 130°C/W junction-to-ambient thermal resistance, and is RoHS-compliant and lead-free (#PBF suffix). This through-hole package supports manual assembly and prototyping while meeting commercial temperature range (0°C to 125°C) specifications.