Analog Devices Inc. LT3579IFE-1#PBF

Overview

LT3579IFE-1#PBF from Analog Devices is a dual-phase capable 6A, 42V monolithic PWM DC/DC converter with integrated master/slave NPN switches (3.4A/2.6A), fault protection (output short, overvoltage, overtemperature), and 200kHz–2.5MHz programmable switching frequency. It supports Boost, SEPIC, Inverting, and Flyback topologies and delivers 12V at 1.7A or –12V at 1.2A from 5V input - ideal for automotive ECU power and TFT-LCD bias supplies.

For engineers reviewing the LT3579IFE-1#PBF datasheet, LT3579IFE-1#PBF pinout, LT3579IFE-1#PBF application, or LT3579IFE-1#PBF equivalent, key selection considerations include its dual-phase synchronization capability via CLKOUT (180° out-of-phase, 50% duty cycle), adjustable UVLO using SHDN, and combined 6A current limit with 250mV V_CE(SAT) at 5.5A.

Technical Context

The LT3579IFE-1#PBF implements constant-frequency current-mode control with internal ramp compensation and sample-mode overcurrent detection. Its dual-phase operation is enabled by the LT3579-1 variant's fixed 50% CLKOUT duty cycle and 180° phase shift relative to the internal oscillator, allowing interleaved switching with matched timing across multiple converters.

It integrates fault logic that triggers shutdown on SW1 overcurrent (>3.4A), combined SW1+SW2 overcurrent (>6A), VIN overvoltage (>16.2V), SW overvoltage (>42V), or junction temperature >165°C. Fault recovery uses SS pin timeout sequencing with charge/discharge cycles between 50mV and 1.8V.

Key Specifications

Pinout & Package

LT3579IFE-1#PBF is housed in a 20-lead plastic TSSOP package with exposed GND pad (Pin 21) requiring PCB soldering for thermal and electrical integrity. θ_JA = 38°C/W, θ_JC = 10°C/W.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar DC/DC controller applications.

Compared with LTC3891EFE#PBF and LT8330EFE#PBF, the LT3579IFE-1#PBF uniquely combines integrated dual NPN switches, 6A combined current, 42V rating, and deterministic 180° phase-shifted CLKOUT - making it the only option for compact, self-contained dual-phase Boost/Inverting regulators with fault-protected outputs.

Availability

LT3579IFE-1#PBF is available at Aetrix Electronics and suitable for automotive ECU power, TFT-LCD bias supplies, vacuum fluorescent display (VFD) bias, and industrial sensor local power supply applications requiring stable component supply across extended temperature ranges.

Supply support for LT3579IFE-1#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 is a global leader in high-performance analog, mixed-signal, and digital signal processing semiconductors, serving precision instrumentation, industrial automation, communications, and automotive markets.

The LT3579 product line delivers monolithic DC/DC controllers with integrated fault protection and multi-topology flexibility - designed specifically for robust, space-constrained local power generation in harsh environments.

FAQ

What is the key functional difference between LT3579IFE-1#PBF and the standard LT3579IFE#PBF?

The LT3579IFE-1#PBF is the dual-phase variant, distinguished by its fixed 50% CLKOUT duty cycle and 180° phase shift relative to the internal oscillator - enabling deterministic interleaving with other LT3579-1 devices. The standard LT3579IFE#PBF has a ~42% CLKOUT duty cycle and no guaranteed phase relationship, limiting it to single-phase or loosely synchronized operation. This makes LT3579IFE-1#PBF essential for reducing input/output ripple in multiphase designs.

How does the LT3579IFE-1#PBF detect and respond to an output short circuit?

The LT3579IFE-1#PBF uses sample-mode overcurrent detection: when FB falls outside regulation (e.g., <45mV in Inverting mode), the IC forces Q1 and Q2 to conduct for minimum on-time each cycle to sample inductor current. If sampled current exceeds 3.4A on SW1 or 6A combined, FAULT pin pulls low, GATE goes high-impedance (disconnecting external PMOS), CLKOUT disables, and SS initiates a timeout sequence. This occurs within microseconds, preventing damage.

Can the LT3579IFE-1#PBF be used in a Flyback configuration, and what are the critical layout considerations?

Yes, the LT3579IFE-1#PBF supports Flyback topology using SW1 and SW2 as primary-side switches with appropriate transformer coupling and snubber design. Critical layout requirements include minimizing SW1/SW2 trace area to reduce EMI, solid grounding of the exposed pad (Pin 21), separate high-current GND returns for power and signal sections, and tight placement of RT, SS, and FB components to avoid noise coupling. The 42V switch rating supports typical Flyback designs up to ~36V output.

What is the role of the GATE pin on the LT3579IFE-1#PBF, and how is it controlled during startup?

On the LT3579IFE-1#PBF, the GATE pin is a programmable pull-down current source (0–933µA) driving the gate of an external PMOS transistor for output disconnect. During startup, GATE current ramps linearly with SS pin voltage: below 500mV, current is negligible; above 500mV, it increases to full 933µA, turning on the PMOS gradually. This soft turn-on limits inrush current and enables safe hot-plug operation - a key safety feature absent in most monolithic converters.

Does the LT3579IFE-1#PBF require external compensation, and where is it connected?

Yes, the LT3579IFE-1#PBF requires external Type II or Type III compensation connected to the VC pin (Pin 19). A series RC network (e.g., 8kΩ + 2.2nF) and feedforward capacitor (e.g., 47pF) are typically used between VC and FB to stabilize the current-mode control loop across all supported topologies (Boost, SEPIC, Inverting, Flyback). Compensation values depend on output voltage, inductance, and load - design equations are provided in the datasheet's Applications Information section.