Analog Devices Inc. LT3650IDD-4.1#PBF

Overview

LT3650IDD-4.1#PBF from Analog Devices (formerly Linear Technology) is a monolithic 2A step-down Li-Ion/Polymer battery charger IC with 4.75V–32V input range, 4.1V float voltage, and integrated 2A switch. It delivers constant-current/constant-voltage charging with programmable C/10 or timer-based termination, preconditioning for deeply discharged batteries, and NTC temperature monitoring. It is used in 12V–24V industrial handhelds and automotive cradle chargers.

For engineers reviewing the LT3650IDD-4.1#PBF datasheet, LT3650IDD-4.1#PBF pinout, LT3650IDD-4.1#PBF application, or LT3650IDD-4.1#PBF equivalent, key selection considerations include its 4.1V float voltage accuracy (±0.5%), 5% charge current accuracy, 1MHz fixed-frequency average current mode control, thermal foldback behavior, and DFN-12 package with exposed ground pad for thermal management.

Technical Context

The LT3650IDD-4.1#PBF implements average current mode control with a 1MHz fixed-frequency buck architecture, using internal 2A switch and bootstrapped BOOST drive to achieve high efficiency across 4.75V–32V inputs. Its voltage error amplifier (V-EA) and current error amplifier (C-EA) jointly regulate BAT voltage and SENSE–BAT differential to maintain precise CC/CV profiles.

It integrates dual termination logic: C/10 detection (triggered at VSENSE–BAT = 10mV ±2.5mV) and user-programmable timer (3-hour default via 0.68µF capacitor on TIMER pin), with bad-battery detection activated if preconditioning fails within 22.5 minutes. Preconditioning initiates below 2.9V BAT and reduces charge current to 15% of programmed IMAX.

Key Specifications

Pinout & Package

LT3650IDD-4.1#PBF is housed in a 3mm × 3mm, 12-pin plastic DFN package with exposed thermal pad (Pin 13 = SGND). The package supports high-power dissipation (θJC = 3°C/W) and requires soldering the exposed pad to PCB ground for thermal and electrical integrity.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LT3650EDD-4.1#PBF, the LT3650IDD-4.1#PBF guarantees full specification compliance over –40°C to 85°C, making it suitable for harsh environments; versus BQ24610RGER, it offers true monolithic integration-reducing external component count by ~7 parts and eliminating gate-drive design risks-while maintaining identical 4.1V float accuracy and thermal safety features.

Availability

LT3650IDD-4.1#PBF is available at Aetrix Electronics and suitable for industrial handheld instruments, 12V–24V automotive cradle chargers, and desktop cradle chargers requiring stable component supply, long-term lifecycle support, and guaranteed extended temperature performance.

Supply support for LT3650IDD-4.1#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 (acquired Linear Technology in 2017) is a global leader in high-performance analog, mixed-signal, and power management semiconductors, serving precision instrumentation, industrial, automotive, and communications markets.

The LT3650 product line was designed as a family of high-input-voltage monolithic Li-Ion chargers targeting industrial and automotive applications where wide VIN range, integrated safety features, and minimal external components are critical.

FAQ

What is the exact float voltage of the LT3650IDD-4.1#PBF, and how tightly is it specified?

The LT3650IDD-4.1#PBF has a nominal float voltage of 4.10V, specified as 4.08V to 4.12V (±0.5%) over temperature and line. This tight tolerance is achieved via laser-trimmed internal reference and applies across the full –40°C to 85°C operating range, ensuring consistent full-charge termination for single-cell Li-Ion and Li-Polymer batteries without external feedback calibration.

Does the LT3650IDD-4.1#PBF require an external blocking diode on the VIN input?

No, the LT3650IDD-4.1#PBF does not require an external blocking diode on VIN. It incorporates internal reverse-voltage protection that prevents battery discharge back into the input supply when VIN is absent or lower than battery voltage. This feature eliminates diode forward-drop losses and simplifies input stage design in 12V/24V-powered systems.

How does the LT3650IDD-4.1#PBF handle deeply discharged batteries below 2.9V?

The LT3650IDD-4.1#PBF automatically enters precondition mode when BAT voltage falls below 2.9V (with 90mV hysteresis). In this mode, it limits charge current to 15% of the programmed maximum (e.g., 300mA for a 2A setup) until BAT rises above the threshold. If the battery fails to respond within 22.5 minutes (1/8 of 3-hour timer), a bad-battery fault is asserted on the FAULT pin.

Can the LT3650IDD-4.1#PBF be configured for timer-only termination without C/10 detection?

Yes - the LT3650IDD-4.1#PBF can be configured for timer-only termination by connecting the TIMER pin to ground. When disabled, C/10 detection remains active but is ignored for termination; instead, charging continues until the full timer interval elapses (e.g., 3 hours with 0.68µF), regardless of current level. This mode is useful for top-off cycles or chemistries requiring fixed-duration CV phases.

What thermal management requirements apply to the LT3650IDD-4.1#PBF in a 2A charging application?

The LT3650IDD-4.1#PBF requires soldering its exposed thermal pad (Pin 13, SGND) to a minimum 200mm² copper pour on the PCB. With θJC = 3°C/W and typical 2A operation at 12V input, junction-to-ambient rise is ~25°C above ambient under natural convection. For continuous 2A charging in enclosed enclosures >60°C ambient, forced airflow or additional thermal vias are recommended to maintain TJ <125°C.