Analog Devices Inc. LT3799IMSE-1#PBF

Overview

LT3799IMSE-1#PBF from Analog Devices (formerly Linear Technology) is an isolated flyback LED controller with active power factor correction, designed for offline AC-driven LED lighting systems. It delivers ±5% typical regulated LED current without opto-couplers, achieves >0.97 typical PFC, and operates in critical conduction mode using a 16-lead MSOP package with exposed thermal pad.

For engineers reviewing the LT3799IMSE-1#PBF datasheet, LT3799IMSE-1#PBF pinout, LT3799IMSE-1#PBF application, or LT3799IMSE-1#PBF equivalent, key selection considerations include primary-side current regulation accuracy, TRIAC-dimmer incompatibility, open/short LED protection via FB/CT fault detection, and VIN_SENSE-based line voltage sensing for PFC compliance in universal-input (90–270V_AC) designs.

Technical Context

The LT3799IMSE-1#PBF implements a novel primary-side current control loop that calculates secondary LED current from primary peak current and DCM timing-eliminating opto-couplers. Its multiplier-based PFC circuit modulates the current limit threshold proportionally to rectified line voltage sensed at VIN_SENSE, enabling >0.97 power factor across 90–270V_AC input.

It uses critical conduction mode (CrCM) with dv/dt-based DCM detection on the transformer's third winding to achieve zero-voltage switching turn-on, improving efficiency by up to 5%. The FAULT pin asserts open/short LED conditions via coordinated monitoring of FB (>1.25V) and CT (>1.25V), with automatic retry via CT capacitor discharge/recharge.

Key Specifications

Pinout & Package

Thermally enhanced 16-lead MSOP package (MSE) with exposed GND pad (Pin 17) requiring PCB soldering for electrical integrity and thermal dissipation (θ_JA = 50°C/W).

Key Features

Applications

Equivalent & Alternatives

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

Compared with UCC28810DR and NCP1654ADR2G, the LT3799IMSE-1#PBF uniquely integrates CrCM flyback control, opto-coupler–free current regulation, and single-chip PFC-reducing total solution size and bill-of-materials for 4W–100W+ offline LED drivers.

Availability

LT3799IMSE-1#PBF is available at Aetrix Electronics and suitable for street lighting, commercial downlights, industrial high-bay fixtures, UV-C disinfection modules, and universal-input LED drivers requiring stable component supply, long-lifecycle support, and automotive-grade reliability validation.

Supply support for LT3799IMSE-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, Inc. (acquired Linear Technology in 2017) is a global leader in high-performance analog, mixed-signal, and power management semiconductors.

The LT3799 product line was developed specifically for cost-effective, high-reliability offline LED drivers requiring integrated PFC and primary-side regulation-targeting architectural, industrial, and outdoor lighting markets.

FAQ

Does the LT3799IMSE-1#PBF support TRIAC dimming?

No, the LT3799IMSE-1#PBF is explicitly not designed for use with TRIAC dimmers. Its control architecture relies on continuous line voltage sensing at VIN_SENSE for PFC, which conflicts with the phase-cut waveform of leading-edge TRIAC dimmers. For dimmable applications, use analog dimming via CTRL pins or PWM dimming synchronized externally-never connect LT3799IMSE-1#PBF directly to a TRIAC dimmer circuit.

What is the function of the DCM pin on the LT3799IMSE-1#PBF?

DCM (Pin 10) detects discontinuous conduction mode by monitoring dv/dt on the transformer's third winding. A series RC network connects to this pin; when secondary current falls to zero, ringing induces a fast voltage transition that triggers internal comparator A2. This timing information is essential for the LT3799IMSE-1#PBF to calculate LED current without secondary-side sensing-and enables zero-voltage switching for improved efficiency.

How does the LT3799IMSE-1#PBF achieve power factor correction without external components?

The LT3799IMSE-1#PBF achieves >0.97 typical PFC using an internal multiplier circuit that scales the current limit threshold proportionally to the voltage at VIN_SENSE. When a resistor divider applies a scaled version of rectified line voltage (1.25–1.5V) to VIN_SENSE, the controller modulates peak primary current in phase with the AC line-ensuring input current follows voltage waveform shape. No external PFC controller or boost stage is needed.

Can the LT3799IMSE-1#PBF operate from 277VAC input?

Yes, the LT3799IMSE-1#PBF supports universal input ranges including 277VAC. Its VIN pin withstands up to 32V DC, so the external startup resistor and bulk capacitor must be rated for ≥400V DC. The VIN_SENSE divider must be recalibrated to deliver 1.25–1.5V at peak 277VAC (≈392V), and transformer turns ratio must ensure VOUT·N remains within SENSE and GATE voltage limits. Reference design 37991 TA01b confirms 220V–277V operation.

What thermal design requirements apply to the LT3799IMSE-1#PBF MSOP package?

The LT3799IMSE-1#PBF uses a 16-lead MSOP with exposed GND pad (Pin 17) that must be soldered to a minimum 100 mm² copper area on the PCB for thermal performance. Thermal resistance is θ_JA = 50°C/W and θ_JC = 10°C/W. To maintain ≤125°C junction temperature in 60W designs, provide ≥2 oz copper, thermal vias under the pad (≥6×0.3mm), and avoid enclosing the IC in sealed housings without forced airflow.