Analog Devices Inc. LT3651EUHE-4.1#TRPBF

Overview

LT3651EUHE-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 high-efficiency charging in automotive cradle chargers and industrial handheld instruments.

For engineers reviewing the LT3651EUHE-4.1#TRPBF datasheet, LT3651EUHE-4.1#TRPBF pinout, LT3651EUHE-4.1#TRPBF application, or LT3651EUHE-4.1#TRPBF equivalent, key selection criteria include programmable 4A charge current, C/10 or timer-based termination, dynamic input current limiting via ILIM, thermal foldback protection, and 36-pin QFN package compatibility with high-power thermal management.

Technical Context

The LT3651EUHE-4.1#TRPBF implements average current mode control using dual error amplifiers (V-EA and C-EA) to regulate constant-current/constant-voltage charging. Its synchronous switcher operates at user-programmable frequency (1.1MHz typical with 50kΩ RT resistor) and integrates soft-start via RNG/SS and ILIM pins.

It features precision analog comparators for preconditioning (2.85V threshold), auto-recharge (97.5% of 4.1V float), bad battery detection (22.5-minute timeout), and thermal shutdown (125°C junction limit). Input current limiting is enforced by clamping ITH based on V_ILIM, while charge current is scaled by V_RNG/SS with 10.8× gain.

Key Specifications

Pinout & Package

LT3651EUHE-4.1#TRPBF uses a 36-pin plastic QFN package (5mm × 6mm, 0.75mm profile) with two exposed thermal pads: Pin 37 (GND) and Pin 38 (SW), both requiring solder connection to PCB for electrical integrity and thermal performance.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LTC4162-L41#TRPBF and BQ24618RGER, the LT3651EUHE-4.1#TRPBF offers superior analog autonomy-no MCU required for preconditioning, timer-based termination, or NTC response-making it ideal for standalone, safety-certifiable charging in harsh environments.

Availability

LT3651EUHE-4.1#TRPBF is available at Aetrix Electronics and suitable for industrial handheld instruments, 12V to 24V automotive and heavy equipment, and desktop cradle chargers requiring stable component supply, long-lifecycle assurance, and RoHS-compliant packaging.

Supply support for LT3651EUHE-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, Inc. (acquired Linear Technology in 2017) is a global leader in high-performance analog, mixed-signal, and power management semiconductors.

The LT3651EUHE-4.1#TRPBF belongs to the Linear Technology LT36xx family of monolithic Li-ion chargers, designed specifically for wide-input, high-current industrial and automotive battery charging where reliability, thermal resilience, and analog autonomy are critical.

FAQ

What is the exact float voltage specification for LT3651EUHE-4.1#TRPBF?

The LT3651EUHE-4.1#TRPBF is factory trimmed to deliver a nominal 4.1V battery float voltage with ±0.5% accuracy over –40°C to 125°C junction temperature. This value is fixed per part number variant and differs from the LT3651-4.2 version (4.2V). The 4.1V setting aligns with standard single-cell Li-ion chemistry requirements and enables precise end-of-charge regulation without external feedback adjustment.

Does LT3651EUHE-4.1#TRPBF support automatic recharge when battery voltage drops?

Yes, the LT3651EUHE-4.1#TRPBF automatically initiates a new charge cycle when the battery voltage at the BAT pin falls to 97.5% of its 4.1V float voltage (i.e., 4.0V). This hysteresis-based auto-recharge function maintains battery readiness without external intervention and is inherent to the IC's analog control architecture-not dependent on microcontroller polling or external timers.

How is input current limiting implemented on LT3651EUHE-4.1#TRPBF?

LT3651EUHE-4.1#TRPBF implements input current limiting via the CLP/CLN sense inputs and ILIM programming pin. A sense resistor between CLP and CLN measures total system input current; voltage across it is compared against a reference derived from V_ILIM. When the limit is exceeded, the IC reduces charge current to maintain constant input draw-enabling stable operation from current-limited sources like USB PD adapters or shared vehicle rails.

Can LT3651EUHE-4.1#TRPBF operate without an NTC thermistor?

Yes, the LT3651EUHE-4.1#TRPBF operates fully functional without an NTC thermistor: the NTC pin (Pin 1) may be left unconnected, disabling temperature monitoring. In this configuration, all other functions-including CC/CV charging, preconditioning, timer/C/10 termination, and fault reporting-remain active. However, thermal safety compliance (e.g., UL 2054, IEC 62133) requires NTC implementation for production use in consumer or medical applications.

What thermal management provisions does LT3651EUHE-4.1#TRPBF include?

The LT3651EUHE-4.1#TRPBF includes junction temperature sensing with thermal foldback: when die temperature exceeds 125°C, charge current is progressively reduced to prevent damage. It also features two exposed thermal pads-Pin 37 (GND) and Pin 38 (SW)-that must be soldered to PCB copper for effective heat conduction. Thermal resistance θ_JA is specified at 43°C/W with proper board layout, enabling sustained 4A operation in industrial ambient conditions.