Analog Devices Inc. LT3799EMSE#TRPBF

Overview

LT3799EMSE#TRPBF from Analog Devices (formerly Linear Technology) is an isolated flyback LED controller with active power factor correction, designed for TRIAC-dimmable offline LED drivers. It delivers ±5% typical LED current regulation without opto-couplers, supports 90–270V_AC input, 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 LT3799EMSE#TRPBF datasheet, LT3799EMSE#TRPBF pinout, LT3799EMSE#TRPBF application, or LT3799EMSE#TRPBF equivalent, key selection considerations include primary-side current sensing architecture, VIN_SENSE-based PFC implementation, FAULT pin behavior during open/short LED events, CT pin fault timing thresholds (240mV low, 1.25V high), and thermal management via exposed GND pad soldering.

Technical Context

The LT3799EMSE#TRPBF implements a novel primary-side current control loop that calculates secondary LED current from primary winding peak current and DCM-detected flyback time-eliminating opto-couplers. Its multiplier-based PFC circuit modulates the current limit threshold proportionally to VIN_SENSE voltage, enabling >0.97 power factor across universal AC inputs.

Critical conduction mode operation is enforced via DCM pin detection of third-winding ringing at zero-current crossing, with blanking time (600ns–2.25µs) preventing false triggering from leakage inductance. The 1.9A gate driver supports external high-voltage MOSFETs, while micropower hysteretic start-up (23V turn-on, 12.3V turn-off) enables direct connection to offline rectified rails.

Key Specifications

Pinout & Package

LT3799EMSE#TRPBF is housed in a thermally enhanced 16-lead plastic MSOP package (MSE) with exposed GND pad (Pin 17), requiring PCB soldering for thermal and electrical integrity. θ_JA = 50°C/W, θ_JC = 10°C/W.

Key Features

Applications

Equivalent & Alternatives

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

Compared with UCC28810DR and NCP1654ADR2G, the LT3799EMSE#TRPBF uniquely integrates TRIAC-dimmable isolated flyback control, opto-coupler–free current regulation, and single-chip PFC-enabling compact, cost-optimized 4W–100W+ LED drivers with no external PFC controller or opto-isolator.

Availability

LT3799EMSE#TRPBF is available at Aetrix Electronics and suitable for street lighting, commercial downlights, industrial high-bay fixtures, and universal-input LED ballasts requiring stable component supply, long-life reliability, and TRIAC dimming compliance.

Supply support for LT3799EMSE#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. (acquired Linear Technology in 2017) is a global semiconductor leader specializing in high-performance analog, mixed-signal, and power management ICs for precision signal chain and power applications.

The LT3799 product line was developed specifically for cost-sensitive, high-reliability offline LED lighting systems requiring integrated PFC, TRIAC dimming, and primary-side regulation-replacing multi-chip solutions with single-IC simplicity.

FAQ

What is the minimum input voltage required to start up the LT3799EMSE#TRPBF?

The LT3799EMSE#TRPBF features micropower hysteretic start-up with a guaranteed turn-on voltage of 23V (typical). This allows reliable startup directly from rectified 90V_AC mains (≈127V_DC peak) without auxiliary windings. The device remains operational down to 12.3V (turn-off threshold), providing 10.7V hysteresis for stable operation across varying bulk capacitor discharge profiles. Startup current is under 70µA before turn-on.

How does the LT3799EMSE#TRPBF achieve power factor correction without an opto-coupler?

The LT3799EMSE#TRPBF achieves >0.97 typical power factor by combining critical conduction mode operation with a proprietary multiplier circuit. The VIN_SENSE pin monitors scaled AC line voltage, and the internal multiplier dynamically adjusts the SENSE pin current limit threshold in proportion to instantaneous line voltage. This forces input current to follow the sinusoidal shape of the input voltage-enabling high PF without secondary-side feedback or opto-couplers.

What protection features are built into the LT3799EMSE#TRPBF?

The LT3799EMSE#TRPBF integrates open LED protection (via FB pin monitoring of third-winding voltage), shorted LED protection (via SENSE pin overcurrent detection), and thermal shutdown (junction-limited to 125°C). Fault conditions trigger the open-drain FAULT pin, which pulls low when FB > 1.25V and CT > 1.25V. Recovery is automatic after CT discharges to 240mV, enabling self-resetting fault handling without system-level intervention.

Can the LT3799EMSE#TRPBF support both 120VAC and 220VAC inputs in the same design?

Yes, the LT3799EMSE#TRPBF supports universal input (90–270V_AC) through its wide VIN operating range (up to 32V absolute max) and scalable VIN_SENSE interface. The datasheet provides optimized schematics for 120V, 220V, and universal configurations. Power factor remains >0.95 and efficiency >85% across both ranges when transformer turns ratio and R_SENSE are selected per application notes. No hardware changes are needed beyond input bridge and bulk capacitor ratings.

What is the role of the DCM pin in the LT3799EMSE#TRPBF?

The DCM (Discontinuous Conduction Mode) pin on the LT3799EMSE#TRPBF connects to a series RC network tied to the transformer's third winding. It functions as a dv/dt detector that identifies zero-current crossing on the secondary side by sensing falling voltage edges. This timing information is essential for the primary-side current calculation algorithm-enabling accurate LED current regulation without opto-couplers. The internal comparator triggers at ≥40µA current flow during the ringing event.