Analog Devices Inc. LT3799EMSE-1#PBF

Overview

LT3799EMSE-1#PBF from Analog Devices (formerly Linear Technology) is an isolated flyback LED controller with active power factor correction, designed for offline AC-powered LED drivers. It delivers ±5% typical regulated LED current without opto-couplers, supports 90–270V_AC input, achieves >0.97 typical PFC, and integrates a 1.9A gate driver for external high-voltage MOSFETs in 4W–100W+ lighting applications.

For engineers reviewing the LT3799EMSE-1#PBF datasheet, LT3799EMSE-1#PBF pinout, LT3799EMSE-1#PBF application, or LT3799EMSE-1#PBF equivalent, this page provides verified technical context, critical conduction mode operation details, primary-side current regulation methodology, fault protection behavior, and validated alternative part guidance for industrial LED driver design.

Technical Context

The LT3799EMSE-1#PBF operates in critical conduction mode (CRM) using third-winding DCM detection to determine flyback timing, enabling accurate primary-side output current calculation without secondary feedback. Its novel control loop employs a multiplier-driven current comparator, sample-and-hold circuitry for open-LED detection, and hysteretic VIN start-up with 23V turn-on/12.3V turn-off thresholds.

It implements active PFC by modulating the peak current limit proportionally to the rectified line voltage sensed at VIN_SENSE, achieving >0.97 power factor. The FAULT pin asserts low on open-LED (FB > 1.25V with CT > 1.25V) or shorted-LED conditions, while internal 10µA CT charging and 200nA discharge enable auto-recovery fault management.

Key Specifications

Pinout & Package

LT3799EMSE-1#PBF is housed in a thermally enhanced 16-lead MSOP package with exposed pad (Pin 17 = GND), requiring soldering of the exposed pad to PCB 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 LT3799EMSE-1#PBF, UCC28810DR requires opto-coupler-based feedback and delivers lower PFC performance, while NCP1654ADR2G offers no LED regulation capability and mandates a second controller-making LT3799EMSE-1#PBF the only single-chip, opto-free, CRM-based solution for compact, high-PF isolated LED drivers.

Availability

LT3799EMSE-1#PBF is available at Aetrix Electronics and suitable for street lighting, industrial high-bay fixtures, and commercial downlights requiring stable component supply, long-lifecycle assurance, and RoHS-compliant packaging.

Supply support for LT3799EMSE-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 (acquired Linear Technology in 2017) is a global leader in high-performance analog, mixed-signal, and power management semiconductors, serving precision instrumentation, industrial automation, and automotive markets.

The LT3799-1 product line was developed specifically for cost-sensitive, high-reliability offline LED drivers needing integrated PFC and primary-side regulation-targeting architectural, outdoor, and industrial lighting where opto-coupler failure is unacceptable.

FAQ

What is the key innovation that allows LT3799EMSE-1#PBF to regulate LED current without an opto-coupler?

The LT3799EMSE-1#PBF uses a novel primary-side sensing method based on critical conduction mode timing and third-winding voltage sampling. By detecting the flyback period via the DCM pin and measuring primary peak current at SENSE, it calculates secondary LED current mathematically-eliminating opto-coupler dependency while maintaining ±5% accuracy. This is confirmed in the device's block diagram and operation section.

Does LT3799EMSE-1#PBF support TRIAC dimming?

No, LT3799EMSE-1#PBF is explicitly not designed for use with TRIAC dimmers, as stated in the official datasheet description: "The LT3799-1 offers improved line regulation over the LT3799, but is not designed for use with a TRIAC dimmer." For dimmable applications, external PWM or analog dimming via CTRL pins is supported instead.

How does the FAULT pin behave during open-LED and shorted-LED conditions?

The FAULT pin on LT3799EMSE-1#PBF is an open-drain output that pulls low during both open-LED (FB > 1.25V with CT > 1.25V) and shorted-LED faults. It remains asserted until the CT capacitor discharges to 240mV, then re-enables switching-but holds FAULT low until FB drops below 1.25V, ensuring robust fault latching and auto-recovery behavior.

What is the recommended minimum value for the CT capacitor, and why?

The CT capacitor value is not fixed-it sets fault timeout duration. With 10µA charge and 200nA discharge currents, a 10nF capacitor yields ~1ms fault hold time before retry. Datasheet Figure 1 shows typical 10nF usage; smaller values reduce recovery time but risk nuisance tripping; larger values increase fault persistence. No absolute minimum is specified, but 1nF is practical lower bound.

Can LT3799EMSE-1#PBF operate from 277V_AC input?

Yes-LT3799EMSE-1#PBF supports universal input up to 305V_AC (430V_DC peak). Its VIN pin withstands 32V, but external components (R_IN, bulk capacitor, MOSFET) must be rated accordingly. The typical application schematic on page 17 confirms operation up to 277V_AC with appropriate transformer turns ratio and R_SENSE selection.