Analog Devices Inc. LT3650EDD-4.1#TRPBF

Overview

LT3650EDD-4.1#TRPBF from Analog Devices (formerly Linear Technology) is a monolithic 2A step-down Li-Ion/Polymer battery charger IC with integrated 2.5A switch, 4.1V float voltage, and 4.75V–32V input range. It delivers constant-current/constant-voltage charging with programmable C/10 or 3-hour timer termination, preconditioning for deeply discharged batteries, and NTC-based temperature monitoring - deployed in 12V–24V automotive cradle chargers and industrial handheld instruments.

For engineers reviewing the LT3650EDD-4.1#TRPBF datasheet, LT3650EDD-4.1#TRPBF pinout, LT3650EDD-4.1#TRPBF application, or LT3650EDD-4.1#TRPBF equivalent, key selection considerations include its 4.1V float voltage accuracy (±0.5%), 100mV current sense threshold, 1MHz fixed-frequency average current mode control, thermal foldback protection, and DFN-12 (3mm × 3mm) package with exposed GND pad.

Technical Context

The LT3650EDD-4.1#TRPBF implements average current mode control using a 1MHz oscillator and internal voltage/current error amplifiers to directly regulate inductor average current via the SENSE–BAT differential voltage. Its architecture integrates a bootstrapped high-side switch (SW pin), BOOST rail generation, and precision analog comparators for C/10 detection (10mV threshold), preconditioning (2.9V BAT threshold), and timer-based bad-battery fault detection (one-eighth of full cycle time).

It supports dual termination modes: C/10 current drop (ITH = 0.1V) or programmable internal timer (3-hour default via 0.68µF on TIMER pin), with auto-restart at 97.5% float voltage and shutdown bias current of 15µA. The RNG/SS pin enables dynamic charge current scaling (0–1V range, 50µA source) and soft-start via external RC.

Key Specifications

Pinout & Package

LT3650EDD-4.1#TRPBF 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 LTC4000-4.1#PBF, LT3650EDD-4.1#TRPBF offers higher integration and smaller solution size but less current headroom; versus BQ24610RGER, it adds critical NTC monitoring and system current limiting at the cost of slightly higher BOM complexity and price.

Availability

LT3650EDD-4.1#TRPBF 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 lead-free compliance.

Supply support for LT3650EDD-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, 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, thermally demanding applications - emphasizing integration, safety features (NTC, bad-battery detection), and robust operation across automotive and industrial temperature ranges.

FAQ

What is the exact float voltage of the LT3650EDD-4.1#TRPBF?

The LT3650EDD-4.1#TRPBF has a nominal float voltage of 4.10 V, specified as 4.08 V (min) to 4.12 V (max) at 25°C, with ±0.5% accuracy over temperature. This value is factory-trimmed and applies exclusively to the -4.1 variant; the -4.2 variant targets 4.20 V. The LT3650EDD-4.1#TRPBF does not support user-adjustable float voltage - it is fixed by internal reference design.

Does the LT3650EDD-4.1#TRPBF require an external blocking diode on the VIN line?

No, the LT3650EDD-4.1#TRPBF does not require an external blocking diode on VIN. Its internal architecture includes reverse-voltage protection that prevents battery discharge back into the input supply when VIN is absent or below battery voltage. This eliminates the 0.3–0.7V forward drop and associated power loss of a discrete diode, improving efficiency and simplifying layout.

How is charge current programmed on the LT3650EDD-4.1#TRPBF?

Charge current on the LT3650EDD-4.1#TRPBF is set by an external sense resistor (R_SENSE) between SENSE and BAT pins, where I_MAX = 0.1V / R_SENSE. For 2A, R_SENSE = 50 mΩ. The RNG/SS pin provides dynamic scaling: applying 0.5V to RNG/SS reduces max current to 1A (50% scaling), per the 0.1 × V_RNG/SS relationship. No DAC or digital interface is needed - analog voltage control suffices.

Can the LT3650EDD-4.1#TRPBF be used with a 5V input supply?

Yes, the LT3650EDD-4.1#TRPBF operates down to 4.75V input, making it compatible with regulated 5V ±5% supplies. However, startup requires either VIN ≥ 7.5V *or* (V_BOOST – V_SW) > 2V - so with 5V input, proper BOOST capacitor charging (e.g., via BAT-connected diode) is essential for reliable initial turn-on. Full 2A operation is achievable at 5V, though efficiency decreases due to higher duty cycle.

What happens during a bad-battery fault on the LT3650EDD-4.1#TRPBF?

During a bad-battery fault - triggered when the battery fails to reach 2.9V within one-eighth of the programmed timer duration - the LT3650EDD-4.1#TRPBF suspends charging, pulls FAULT low, sets CHRG to high-Z, and disables the switch. If timer termination is enabled, the timer pauses. The fault clears automatically only upon removal and replacement of the faulty battery; no manual reset is required. The LT3650EDD-4.1#TRPBF then initiates a new precondition cycle.