Analog Devices Inc. LT3650IDD-4.2#TRPBF

Overview

LT3650IDD-4.2#TRPBF from Analog Devices (formerly Linear Technology) is a monolithic 2A step-down Li-Ion/Polymer battery charger IC with 4.75V–32V input range, 4.2V float voltage, and integrated 2.5A switch. It delivers constant-current/constant-voltage charging with C/10 or programmable 3-hour timer termination, preconditioning for deeply discharged batteries, and NTC-based temperature monitoring. It is used in 12V–24V automotive cradle chargers requiring robust high-voltage battery management.

For engineers reviewing the LT3650IDD-4.2#TRPBF datasheet, LT3650IDD-4.2#TRPBF pinout, LT3650IDD-4.2#TRPBF application, or LT3650IDD-4.2#TRPBF equivalent, key selection criteria include its 4.2V float accuracy (±0.5%), 5% charge current accuracy, 85µA standby current, CLP-based system current limiting, and DFN-12 (3mm × 3mm) thermal performance with exposed GND pad.

Technical Context

The LT3650IDD-4.2#TRPBF employs average current mode control at 1MHz fixed frequency to directly regulate inductor current via SENSE–BAT differential sensing. Its internal 2.5A switch uses BOOST-supplied gate drive for low 350mV on-drop at 2A, enabling >90% efficiency across 12V–20V inputs.

Charge termination is configurable: C/10 detection (10mV sense threshold) or internal timer (3-hour default via 0.68µF capacitor on TIMER pin). Preconditioning activates below 2.9V BAT with 15% reduced current; auto-recharge triggers at 97.5% of 4.2V float (i.e., 4.10V); bad-battery detection halts charging if precondition persists beyond 22.5 minutes.

Key Specifications

Pinout & Package

LT3650IDD-4.2#TRPBF is housed in a 12-pin 3mm × 3mm plastic DFN package with exposed thermal pad (Pin 13 = SGND), rated for –40°C to +85°C ambient operation. The package supports high power density and efficient heat dissipation when the exposed pad is soldered to a multilayer PCB ground plane.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LTC4000EMS#PBF and BQ24610RGET, the LT3650IDD-4.2#TRPBF delivers best-in-class integration for 2A single-cell charging-combining monolithic switch, CLP-based current arbitration, ±0.5% float accuracy, and dual C/10/timer termination in a 3mm × 3mm DFN, reducing solution size and component count without sacrificing safety or precision.

Availability

LT3650IDD-4.2#TRPBF is available at Aetrix Electronics and suitable for industrial handheld instruments, 12V to 24V automotive chargers, and desktop cradle chargers requiring stable component supply, long-term lifecycle support, and guaranteed lead-free compliance.

Supply support for LT3650IDD-4.2#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) is a global leader in high-performance analog, mixed-signal, and power management semiconductors, serving industrial, automotive, communications, and healthcare markets.

The LT3650 product line was designed specifically for high-input-voltage, monolithic Li-ion battery charging in space-constrained, thermally demanding environments-emphasizing integration, safety, and reliability over wide temperature and input ranges.

FAQ

What is the exact float voltage specification for LT3650IDD-4.2#TRPBF?

The LT3650IDD-4.2#TRPBF has a nominal float voltage of 4.2V with guaranteed accuracy of ±0.5% (4.18V to 4.22V) over the full –40°C to +85°C operating temperature range. This value is factory-trimmed and applies specifically to the -4.2 variant; the -4.1 version is 4.1V. The 4.2V setting matches standard single-cell Li-ion chemistry requirements and is referenced internally to enable precise CV-mode regulation.

How does the CLP pin function in LT3650IDD-4.2#TRPBF, and what design impact does it have?

The CLP pin in LT3650IDD-4.2#TRPBF enables system-level input current limiting by servoing the battery charge current to maintain a user-defined total input current budget. When a sense resistor connects CLP to VIN, the IC reduces charge current if system load draws additional current-preventing upstream supply overload. This feature is critical in shared-rail applications like automotive cradles, where the same 12V source powers both the charger and auxiliary circuits.

Can LT3650IDD-4.2#TRPBF operate without an NTC thermistor, and what happens to safety functions?

Yes, LT3650IDD-4.2#TRPBF can operate without an NTC thermistor: the NTC pin is left unconnected, disabling temperature monitoring. In this configuration, all NTC-related safety functions-including automatic charge suspension below 0°C or above 40°C and FAULT pin assertion on thermal violation-are inactive. Battery charging proceeds normally, but thermal protection is forfeited. For safety-critical applications, Analog Devices recommends retaining the 10kΩ B=3380 NTC network.

What is the purpose of the RNG/SS pin in LT3650IDD-4.2#TRPBF, and how is it used for soft-start?

The RNG/SS pin in LT3650IDD-4.2#TRPBF sources a precise 50µA current and serves two roles: dynamic charge current programming and soft-start control. For soft-start, a capacitor (C_RNG/SS) is connected from RNG/SS to ground; the time to charge it to 1V determines the ramp-up interval (t_SS = C_RNG/SS / 50µA). This limits inrush current during startup, protecting input capacitors and upstream supplies-especially valuable in high-capacitance battery systems.

Does LT3650IDD-4.2#TRPBF support automatic recharge, and at what voltage threshold does it trigger?

Yes, LT3650IDD-4.2#TRPBF supports automatic recharge: it restarts a full charging cycle when the battery voltage at the BAT pin drops to 97.5% of the float voltage (i.e., 4.10V for the 4.2V variant). This threshold is internally generated and fixed-no external components are required. Auto-recharge ensures the battery remains at full capacity during intermittent use, and occurs only after full termination into standby mode (85µA), minimizing unnecessary cycling.