Analog Devices Inc. LT3741IUF-1#PBF

Overview

LT3741IUF-1#PBF from Analog Devices (formerly Linear Technology) is a fixed-frequency synchronous step-down DC/DC controller optimized for high-accuracy constant-current and constant-voltage regulation up to 20A. It features average current-mode control, ±6% current regulation accuracy, ±1.5% voltage regulation accuracy, and supports input voltages from 6V to 36V with output voltage range up to (VIN – 2V). It is used in super-capacitor charging systems requiring precise current limiting and robust short-circuit protection.

For engineers reviewing the LT3741IUF-1#PBF datasheet, LT3741IUF-1#PBF pinout, LT3741IUF-1#PBF application, or LT3741IUF-1#PBF equivalent, key selection considerations include its dual CTRL pin thermal derating capability, 20-lead 4mm × 4mm QFN package with exposed GND pad, programmable 200kHz–1MHz switching frequency, and ability to source/sink current - distinguishing it from the standard LT3741.

Technical Context

The LT3741IUF-1#PBF implements average current-mode control using internal gm amplifiers (475 µA/V for current loop, 850 µA/V for voltage loop) and a 2V buffered reference (VREF) with 0.5mA drive capability. Its unique architecture enables bidirectional current regulation via SENSE+ and SENSE– differential sensing, with common-mode lockout (0V to VIN–2V), cycle-by-cycle overcurrent protection, and 13µs overvoltage shutdown at FB >1.5V.

Unlike the LT3741, the LT3741-1 variant (including LT3741IUF-1#PBF) integrates a zero-cross comparator in the block diagram to eliminate shoot-through during light-load or discontinuous conduction mode, improving efficiency and stability in high-current, low-duty-cycle applications such as battery formation or LED driver biasing.

Key Specifications

Pinout & Package

LT3741IUF-1#PBF is housed in a thermally enhanced 20-lead 4mm × 4mm plastic QFN package with an exposed GND pad (Pin 21) that must be soldered to PCB for thermal and electrical integrity. The package supports high-current power delivery and efficient heat dissipation in compact layouts.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LTC3776EUF#PBF and LT8705IUHF#PBF, LT3741IUF-1#PBF delivers superior thermal derating via dedicated CTRL2 input and zero-cross protection for DCM operation - making it uniquely suited for precision supercapacitor charging and industrial battery formation where analog control fidelity and bidirectional capability are mandatory.

Availability

LT3741IUF-1#PBF is available at Aetrix Electronics and suitable for supercapacitor charging, LED biasing, industrial battery formation, and high-current test equipment requiring stable component supply, long-term lifecycle support, and guaranteed traceable sourcing.

Supply support for LT3741IUF-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 (ADI) is a global leader in high-performance analog, mixed-signal, and power management ICs, formed through the acquisition of Linear Technology in 2017.

The LT3741/LT3741-1 product line was designed specifically for high-accuracy, high-current constant-current and constant-voltage DC/DC conversion in industrial energy storage, lighting, and test instrumentation applications.

FAQ

What is the key functional difference between LT3741IUF-1#PBF and LT3741IUF#PBF?

The LT3741IUF-1#PBF incorporates a zero-cross comparator in its control architecture - absent in the standard LT3741IUF#PBF - which actively prevents shoot-through during discontinuous conduction mode. This improves light-load efficiency and stability in high-current, low-duty-cycle applications such as supercapacitor charging. Both share identical pinout, package, and temperature rating, but LT3741IUF-1#PBF is preferred where DCM operation is frequent or unavoidable. The LT3741IUF-1#PBF also disables sinking capability in certain configurations per datasheet Figure 2.

Can LT3741IUF-1#PBF regulate both constant current and constant voltage simultaneously?

Yes, LT3741IUF-1#PBF operates in dual-loop mode: the average current-mode loop regulates inductor current (set by CTRL1/CTRL2), while the voltage loop (via FB pin) engages once output reaches the programmed level. When voltage regulation activates, the controller reduces inductor current to maintain the FB-set voltage - enabling seamless transition between CC and CV modes, as verified in Typical Application TA01a and G19–G22 performance curves.

What is the maximum supported output current for LT3741IUF-1#PBF, and how is it set?

LT3741IUF-1#PBF supports up to 20A regulated output current, determined by the external sense resistor (RS) and CTRL1 voltage: I_OUT = V_CTRL1 / (30 × R_S). For example, with V_CTRL1 = 1.5V and R_S = 2.5mΩ, maximum current is 20A. The datasheet Table 1 confirms 20A is achievable with 2mΩ RS; power dissipation in RS is calculated as (0.05V)²/R_S, requiring appropriate resistor wattage rating.

Does LT3741IUF-1#PBF require external components for gate driving, and what MOSFET parameters are critical?

Yes, LT3741IUF-1#PBF drives external high-side and low-side N-channel MOSFETs. Critical MOSFET parameters include: R_DS(ON) (for conduction loss), total gate charge Q_G (for driver power loss), Q_GD/Q_GS (for switching loss), and V_GS(th) < 2V (to ensure reliable turn-on at 3–5V gate drive). The datasheet recommends Renesas RJK0365DPA (top) and RJK0330DPB (bottom) for 24V/20A operation, with matching Q_G and R_DS(ON) values.

How does the CTRL2 pin function in LT3741IUF-1#PBF, and what thermal protection does it provide?

The CTRL2 pin in LT3741IUF-1#PBF accepts an analog voltage (0–1.5V) that dynamically scales the regulated output current downward as temperature increases - enabling active thermal derating without shutting down. When used with an NTC thermistor divider, it reduces current before reaching the 163°C thermal shutdown threshold, preserving system uptime. The lower of CTRL1 and CTRL2 voltages always determines final current limit, as confirmed in the OPERATION section and Figure 1 block diagram.