Analog Devices Inc. LT3650IMSE-4.2#PBF

Overview

LT3650IMSE-4.2#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, 4.2V 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 - used in 12V–24V automotive cradle chargers and industrial handheld instruments.

For engineers reviewing the LT3650IMSE-4.2#PBF datasheet, LT3650IMSE-4.2#PBF pinout, LT3650IMSE-4.2#PBF application, or LT3650IMSE-4.2#PBF equivalent, key selection considerations include its 4.2V float accuracy (±0.5%), 1MHz average current mode control, MSOP-12 package thermal performance, and dual termination options (C/10 vs. 3-hour safety timer).

Technical Context

The LT3650IMSE-4.2#PBF implements a fixed-frequency (1MHz) average current mode buck regulator architecture with internal 2A switch and bootstrapped gate drive (BOOST pin). Its control loop directly regulates average inductor current via SENSE–BAT differential sensing and integrates voltage error (BAT vs. 4.2V reference) to generate ITH, which sets current limit.

It supports two independent termination schemes: analog C/10 detection (VSENSE–VBAT = 10mV ±2.5mV) or programmable timer (3h typical with 0.68µF on TIMER pin), with bad-battery detection triggered if preconditioning fails within 22.5 minutes. Preconditioning activates below 2.9V BAT and reduces charge current to 15% of programmed IMAX.

Key Specifications

Pinout & Package

LT3650IMSE-4.2#PBF is housed in a 12-lead plastic MSOP package (3mm × 4.9mm, 0.65mm pitch) with exposed thermal pad (Pin 13 = SGND). The package supports high-power dissipation (θJA = 43°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 charging applications.

Compared with MP2617GQ-Z and BQ24610RGER, the LT3650IMSE-4.2#PBF uniquely combines integrated 2A switching, dual termination modes (C/10 + timer), and autonomous preconditioning - delivering higher functional integration and reduced design risk for mid-power industrial chargers.

Availability

LT3650IMSE-4.2#PBF is available at Aetrix Electronics and suitable for industrial handheld instruments, 12V to 24V automotive cradle chargers, and desktop cradle chargers requiring stable component supply, long-lifecycle support, and guaranteed lead-free compliance.

Supply support for LT3650IMSE-4.2#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 industrial, automotive, communications, and healthcare markets.

The LT3650 product line was designed specifically for high-input-voltage, monolithic Li-Ion charging in space-constrained industrial and automotive applications - emphasizing integration, thermal robustness, and autonomous safety features without external controllers.

FAQ

What is the exact float voltage accuracy of the LT3650IMSE-4.2#PBF?

The LT3650IMSE-4.2#PBF guarantees a float voltage of 4.20V with ±0.5% accuracy over temperature and line conditions, meaning the actual regulated battery voltage remains within 4.18V to 4.22V. This tight tolerance ensures compliance with Li-Ion cell manufacturer specifications and prevents overvoltage stress that could reduce cycle life or cause safety hazards. The 0.5% figure is specified across –40°C to 85°C ambient and applies to all LT3650IMSE-4.2#PBF units in production.

Does the LT3650IMSE-4.2#PBF support both C/10 and timer-based charge termination simultaneously?

No - the LT3650IMSE-4.2#PBF supports either C/10 termination or timer-based termination, selected by the configuration of the TIMER pin. When TIMER is grounded, C/10 detection is active; when a capacitor is connected to TIMER, the internal timer governs termination. During timer operation, C/10 detection still occurs and drives the CHRG pin low, but the full charge cycle continues until timer expiration. The LT3650IMSE-4.2#PBF does not combine both methods into a single logical AND/OR decision.

Can the LT3650IMSE-4.2#PBF be used with input voltages below 7.5V?

The LT3650IMSE-4.2#PBF requires ≥7.5V on VIN to start up under normal conditions, but can operate down to 4.75V once running - provided the BOOST–SW voltage remains >2V. This is achieved by connecting the BOOST capacitor's anode to a stable ≥5V source (e.g., regulated 5V rail or battery) instead of VIN. Without this external BOOST supply, startup below 7.5V is not supported. All LT3650IMSE-4.2#PBF operating specifications assume VIN ≥ 7.5V for initial enablement.

How does the LT3650IMSE-4.2#PBF implement bad-battery detection?

The LT3650IMSE-4.2#PBF triggers bad-battery detection if the battery voltage fails to rise above 2.9V during preconditioning within one-eighth of the programmed timer duration (e.g., 22.5 minutes for a 3-hour timer). Upon detection, charging halts, CHRG goes high-impedance, and FAULT is pulled low. The condition clears automatically when the faulty battery is removed and replaced - no reset signal or power cycle is needed. This behavior is inherent to the LT3650IMSE-4.2#PBF's analog state machine and requires no firmware.

What is the thermal performance difference between the MSOP and DFN packages for the LT3650IMSE-4.2#PBF?

Both the LT3650IMSE-4.2#PBF (MSOP-12) and LT3650IDD-4.2#PBF (DFN-12) share identical θJA = 43°C/W and θJC = 3°C/W thermal resistance values when their exposed pads are properly soldered to a 1-in² copper pour. However, the MSOP package has a larger body (3mm × 4.9mm vs. 3mm × 3mm) and longer leads, offering slightly better mechanical stability and easier rework - while the DFN provides superior power density. Thermal performance in practice depends more on PCB layout than package choice for the LT3650IMSE-4.2#PBF.