Analog Devices Inc. LT3651IUHE-4.1#TRPBF

Overview

LT3651IUHE-4.1#TRPBF from Analog Devices (formerly Linear Technology) is a monolithic 4A synchronous step-down Li-ion battery charger IC for single-cell applications, supporting 6.5V–32V input and delivering 4.1V float voltage with 0.5% accuracy, 7.5% charge current accuracy, and NTC-based temperature monitoring. It enables automotive cradle chargers, industrial handheld instruments, and notebook computers requiring high-efficiency CC/CV charging.

For engineers reviewing the LT3651IUHE-4.1#TRPBF datasheet, LT3651IUHE-4.1#TRPBF pinout, LT3651IUHE-4.1#TRPBF application, or LT3651IUHE-4.1#TRPBF equivalent, key selection criteria include input voltage range up to 32V, programmable 4A charge current, C/10 or timer-based termination, thermal foldback protection, and 36-pin QFN package with exposed SW and GND pads.

Technical Context

The LT3651IUHE-4.1#TRPBF implements average current mode control using dual error amplifiers: V-EA regulates BAT voltage against 4.1V internal reference, while C-EA compares scaled ITH against SENSE–BAT voltage to enforce precise constant-current regulation. Its synchronous switcher uses bootstrapped high-side drive (BOOST pin) and MOSFET low-side switching for >85% efficiency at 24V_IN/3.9V_BAT.

Charge sequencing includes automatic preconditioning below 2.85V, auto-recharge at 97.5% float voltage (3.9975V), and bad battery detection triggered if precondition persists beyond 22.5 minutes. Input current limiting is enforced via CLP/CLN sense resistor feedback controlled by ILIM pin voltage, with 11.5V/V gain scaling.

Key Specifications

Pinout & Package

LT3651IUHE-4.1#TRPBF is housed in a 5mm × 6mm 36-pin plastic QFN package with two exposed thermal pads: Pin 37 (GND) and Pin 38 (SW). Both must be soldered to PCB copper for thermal management and electrical integrity. The package supports high-current switching with multiple SW and GND pins distributed across the periphery.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar Li-ion battery charger applications.

Compared with BQ24610RGER and MP2617GQZ, the LT3651IUHE-4.1#TRPBF uniquely combines 4.1V precision float, integrated synchronous switching, NTC monitoring, and dual-loop (battery + input) current control - making it optimal for industrial and automotive systems demanding robustness, safety, and supply-aware charging.

Availability

LT3651IUHE-4.1#TRPBF is available at Aetrix Electronics and suitable for automotive cradle chargers, industrial handheld instruments, notebook computer docks, and desktop battery cradles requiring stable component supply, extended temperature operation (–40°C to 125°C), and long-term lifecycle support.

Supply support for LT3651IUHE-4.1#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 full product support, documentation, and manufacturing continuity for all Linear ICs including the LT3651 family.

The LT3651 product line was designed specifically for high-voltage, high-current Li-ion charging in harsh environments - targeting automotive, industrial, and medical applications where input transients, thermal stress, and safety certification are critical.

FAQ

What is the exact float voltage specification for LT3651IUHE-4.1#TRPBF?

The LT3651IUHE-4.1#TRPBF has a nominal float voltage of 4.1V with guaranteed accuracy of ±0.5% over –40°C to 125°C junction temperature. This is confirmed in the Electrical Characteristics table (Page 3) where V_BAT(FLT) for LT3651-4.1 is specified as 4.08V to 4.12V at T_J = –40°C to 125°C. The part number suffix "-4.1" explicitly denotes this 4.1V variant.

Does LT3651IUHE-4.1#TRPBF support both C/10 and timer-based charge termination?

Yes, the LT3651IUHE-4.1#TRPBF supports both termination methods. C/10 termination occurs when charge current falls to 10% of the programmed maximum (e.g., 400mA for 4A); timer termination is user-programmable via a capacitor on the TIMER pin, defaulting to 3 hours with 0.68µF. The datasheet confirms selectable termination in the FEATURES and OPERATION sections.

How does LT3651IUHE-4.1#TRPBF implement input current limiting?

The LT3651IUHE-4.1#TRPBF uses differential sensing across CLP and CLN pins to monitor system input current. The ILIM pin voltage (0–1V) sets the target voltage across the CLP–CLN sense resistor via 11.5V/V gain. When sensed voltage exceeds this target, the IC reduces charge current to maintain constant input current - enabling supply-aware charging in multi-load systems.

What thermal protection mechanisms are built into LT3651IUHE-4.1#TRPBF?

The LT3651IUHE-4.1#TRPBF includes die temperature foldback, which progressively reduces charge current above a thermal threshold to prevent overheating. It also integrates NTC-based battery temperature monitoring (0.29V–1.36V range) that halts charging outside 0°C–40°C. Both features are documented in the FEATURES list and OPERATION section, with thermal foldback curves shown in Figure G06.

Is LT3651IUHE-4.1#TRPBF compatible with standard 10kΩ NTC thermistors?

Yes, the LT3651IUHE-4.1#TRPBF is designed for use with standard 10kΩ NTC thermistors having B-value 3380. The NTC pin sources 50µA and monitors voltage between 0.29V (low-temp limit) and 1.36V (high-temp limit), matching the typical voltage swing of such thermistors across 0°C–40°C. This compatibility is explicitly stated in the PIN FUNCTIONS section (Page 7).