Analog Devices Inc. LT3743IFE#TRPBF

Overview

LT3743IFE#TRPBF from Analog Devices (formerly Linear Technology) is a fixed-frequency synchronous step-down DC/DC controller optimized for high-current LED driving with three-state current control. It delivers up to 20A regulated LED current, supports 6V–36V input, achieves ±6% current regulation accuracy, and enables sub-2µs transitions between two current levels-used in DLP projectors for precise RGB color mixing.

For engineers reviewing the LT3743IFE#TRPBF datasheet, LT3743IFE#TRPBF pinout, LT3743IFE#TRPBF application, or LT3743IFE#TRPBF equivalent, key selection criteria include its dual-analog-control architecture (CTRL_L/CTRL_H), switched-capacitor PWM dimming topology, 200kHz–1MHz programmable switching frequency, and TSSOP-28 package with exposed thermal pad.

Technical Context

The LT3743IFE#TRPBF implements average current mode control with two independent analog reference inputs (CTRL_L and CTRL_H), each routed through dedicated compensation networks (VCL/VCH) to maintain loop stability during rapid state transitions. Its unique switched-output-capacitor topology uses PWMGH/PWMGL to select between two external capacitors-one precharged to the forward voltage at the low current level, the other at the high level-enabling <2µs recovery between regulated states.

Overcurrent protection is cycle-by-cycle and tied directly to the CTRL_H-set current level plus a fixed 23mV offset across SENSE+–SENSE−. Voltage regulation and open-LED protection are implemented via the FB pin (1.0V reference), with lockout triggered at 1.3V and 13µs forced discharge of the inductor through both output capacitors.

Key Specifications

Pinout & Package

LT3743IFE#TRPBF is housed in a 28-lead plastic TSSOP package with an exposed thermal pad (Pin 29) that must be soldered to the PCB for thermal and electrical grounding. The package measures standard TSSOP dimensions and is rated for –40°C to +125°C junction temperature.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar high-current LED driver controller applications.

Compared with LTC3783EFE#PBF and LM3409QMH/NOPB, the LT3743IFE#TRPBF uniquely delivers microsecond-level current state switching, dual-analog reference control, and integrated protection for 20A-class LED systems-making it the only option for high-fidelity RGB projection and professional stage lighting.

Availability

LT3743IFE#TRPBF is available at Aetrix Electronics and suitable for DLP projectors, high-power architectural lighting, laser diode drivers, and stage lighting systems requiring stable component supply, long-term lifecycle support, and traceable sourcing.

Supply support for LT3743IFE#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 acquired Linear Technology in 2017 and maintains its high-performance analog IC portfolio, emphasizing precision power management, signal conditioning, and timing solutions for demanding industrial and automotive applications.

The LT3743 product line was designed specifically for high-current, high-dynamic-range LED driving-targeting applications where color fidelity, fast dimming response, and robust fault protection are non-negotiable.

FAQ

What is the maximum LED current supported by the LT3743IFE#TRPBF?

The LT3743IFE#TRPBF supports up to 20A regulated LED current when paired with appropriately rated external MOSFETs and thermal management. This is achieved using average current mode control with ±6% accuracy across the 6V–36V input range. The actual achievable current depends on PCB layout, heatsinking, and MOSFET selection-designs must ensure θJA remains ≤30°C/W per the TSSOP-28 package specification. LT3743IFE#TRPBF does not integrate power switches; all current-handling is external.

How does the LT3743IFE#TRPBF achieve 3000:1 PWM dimming ratio?

The LT3743IFE#TRPBF achieves up to 3000:1 PWM dimming ratio through its unique switched-capacitor topology and dual-reference architecture. By using CTRL_SEL to toggle between two independently regulated current levels (set by CTRL_H and CTRL_L) and precharging external output capacitors to their respective LED forward voltages, the LT3743IFE#TRPBF transitions between states in under 2µs-eliminating color shift and enabling true-color dimming. This is distinct from conventional PWM dimming and is validated in typical application waveforms (e.g., Figure 3743 G29–G33).

What is the role of the VCL and VCH pins on the LT3743IFE#TRPBF?

VCL (Pin 15) and VCH (Pin 16) provide separate compensation networks for the average current mode control loop during low-level and high-level current regulation, respectively. Each connects to an RC network (typically 15k–80kΩ + 2nF–10nF) that stabilizes the error amplifier for its designated state. This dual-compensation design prevents loop instability when rapidly switching between CTRL_L and CTRL_H references-a key enabler of the LT3743IFE#TRPBF's sub-2µs recovery time and reliable 3000:1 dimming performance.

Does the LT3743IFE#TRPBF support synchronization to an external clock?

Yes, the LT3743IFE#TRPBF supports external clock synchronization via the SYNC pin (Pin 18). When enabled, the internal oscillator locks to an external clock signal in the 240kHz–1.2MHz range. To avoid beat frequencies, the RT resistor must be configured to set the free-running frequency ~20% lower than the SYNC frequency. The SYNC pin must be grounded when unused. This feature allows precise timing alignment across multiple LT3743IFE#TRPBF controllers in multi-channel LED systems-critical for synchronized color mixing in projection and stage lighting.

What protection features are integrated into the LT3743IFE#TRPBF?

The LT3743IFE#TRPBF integrates cycle-by-cycle overcurrent protection (triggered when SENSE+–SENSE− exceeds CTRL_H-set level +23mV), open-LED detection (via FB pin threshold at 1.3V), overvoltage regulation (FB = 1.0V reference), thermal derating via CTRL_T input, and UVLO on the EN/UVLO pin (1.55V turn-on, 130mV hysteresis). All protections operate without external components. During open-LED fault, LT3743IFE#TRPBF disables switching for 13µs and actively discharges the inductor through both output capacitors-ensuring safe energy dissipation.