Analog Devices Inc. LT3650IDD-8.2#PBF

Overview

LT3650IDD-8.2#PBF from Analog Devices (formerly Linear Technology) is a monolithic 2-cell Li-Ion/Polymer battery charger IC with integrated 2A switch, operating from 9V to 32V input and delivering 8.2V float voltage. It features programmable charge current up to 2A via external sense resistor, C/10 or timer-based termination (3-hour default), and NTC-based temperature monitoring. It is used in 12V–24V automotive and industrial battery charging systems requiring high-voltage input compatibility and autonomous safety management.

For engineers reviewing the LT3650IDD-8.2#PBF datasheet, LT3650IDD-8.2#PBF pinout, LT3650IDD-8.2#PBF application, or LT3650IDD-8.2#PBF equivalent, this page provides verified technical context, exact pin functions, real-world charge termination behavior, thermal fault response, and validated alternative parts for 2-cell Li-Ion charging designs where input voltage exceeds 11.5V and float accuracy ≤0.5% is required.

Technical Context

The LT3650IDD-8.2#PBF implements a fixed-frequency (1MHz) average current mode step-down architecture with bootstrapped gate drive for its internal 2.5A switch. Its control loop directly regulates average inductor current using SENSE–BAT differential voltage feedback and integrates voltage error (V-EA) and current error (C-EA) amplifiers to maintain precise CC/CV profiles.

It supports dual termination modes: C/10 detection (7.5–12.5mV sense threshold) or internal timer (3-hour default via 0.68µF capacitor on TIMER pin), with bad-battery detection triggered if preconditioning fails within 22.5 minutes. The RNG/SS pin enables dynamic charge current scaling (0–1V range, 50µA source) and soft-start implementation without external op-amps.

Key Specifications

Pinout & Package

LT3650IDD-8.2#PBF uses a 12-lead (3mm × 3mm) plastic DFN package with exposed thermal pad (Pin 13 = GND). The package is rated for –40°C to +85°C operation and requires soldering of 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 2-cell Li-Ion charging applications.

Compared with LTC4000-8.2#PBF and BQ24610RGER, the LT3650IDD-8.2#PBF delivers fully integrated 2A charging with built-in NTC interface, bad-battery detection, and DFN-12 packaging - reducing component count, layout area, and qualification effort for mid-power 2-cell Li-Ion systems operating from 12V/24V sources.

Availability

LT3650IDD-8.2#PBF is available at Aetrix Electronics and suitable for automotive telematics, industrial handheld scanners, desktop cradle chargers, and heavy equipment data loggers requiring stable component supply and guaranteed –40°C to +85°C operation.

Supply support for LT3650IDD-8.2#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.

The LT3650 product line was designed specifically for high-input-voltage, monolithic 2-cell Li-Ion/Polymer charging in space-constrained industrial and automotive applications where reliability, thermal safety, and autonomous fault handling are critical.

FAQ

What is the exact float voltage specification for LT3650IDD-8.2#PBF?

The LT3650IDD-8.2#PBF is factory-trimmed to deliver a nominal 8.2V float voltage with ±0.04V (±0.5%) accuracy over temperature and line. This value is confirmed in the Electrical Characteristics table (VBAT(FLT) parameter) and applies across the full –40°C to +85°C operating range. The 8.2V designation in the part number directly reflects this precise regulation target for 2-cell Li-Ion chemistry.

Does LT3650IDD-8.2#PBF support automatic recharge, and at what threshold?

Yes, the LT3650IDD-8.2#PBF supports automatic recharge when the battery voltage drops 2.5% below the float voltage - i.e., at 8.015V for the 8.2V variant. This behavior is hardwired and does not require external configuration. Upon detecting this voltage drop, the IC exits standby mode (85µA) and initiates a new full CC/CV charge cycle, ensuring battery readiness without host intervention.

How is the maximum charge current set on LT3650IDD-8.2#PBF?

The maximum charge current for LT3650IDD-8.2#PBF is set by an external current-sense resistor (R_SENSE) connected between SENSE and BAT pins. The relationship is R_SENSE = 0.1V / I_CHG(MAX). For example, a 50mΩ resistor sets I_CHG(MAX) = 2A. The RNG/SS pin can dynamically scale this value downward (0–100%) but cannot exceed the R_SENSE-defined upper limit.

Can LT3650IDD-8.2#PBF operate without an NTC thermistor?

Yes, the LT3650IDD-8.2#PBF operates fully without an NTC thermistor. The NTC function is disabled by leaving Pin 8 (NTC) unconnected; the IC will not monitor temperature or assert faults related to it. However, omitting NTC removes critical thermal safety coverage - Analog Devices recommends retaining it for automotive, industrial, or any application where battery temperature excursions are possible.

What is the purpose of the CLP pin on LT3650IDD-8.2#PBF, and is it mandatory?

The CLP pin on LT3650IDD-8.2#PBF enables system-level input current limiting by servoing the battery charge current to maintain a user-defined total input current. It is not mandatory: if unused, CLP must be tied directly to VIN. When implemented, it allows shared input rails (e.g., in multi-port docks) to avoid overloading upstream supplies - a feature absent in most competing monolithic chargers.