Analog Devices Inc. LTC4009CUF-2#TRPBF

Overview

LTC4009CUF-2#TRPBF from Analog Devices (formerly Linear Technology) is a synchronous buck battery charger controller optimized for lithium-ion/polymer battery packs with 1–4 series cells. It delivers ±0.5% output float voltage accuracy at 4.2 V/cell, supports programmable charge current (±4% accuracy), and features AC adapter input current limiting with 3% accuracy. Used in notebook computers and portable instruments, it enables high-efficiency charging (up to 95%) without audible noise using ceramic capacitors.

For engineers reviewing the LTC4009CUF-2#TRPBF datasheet, LTC4009CUF-2#TRPBF pinout, LTC4009CUF-2#TRPBF application, or LTC4009CUF-2#TRPBF equivalent, key selection criteria include its pin-programmable 4.2 V/cell output, 20-pin 4 mm × 4 mm QFN package, 550 kHz switching frequency, wide 6 V–28 V input range, and integrated ICL/CHRG/ACP status indicators for microcontroller-based charge management.

Technical Context

The LTC4009CUF-2#TRPBF implements a current-mode synchronous buck PWM architecture with quasi-constant 550 kHz switching frequency, eliminating audible noise with ceramic bulk capacitors. Its dual-loop control simultaneously regulates charge current via PROG pin feedback and battery voltage via FVS0/FVS1 digital select pins - fixed to 4.2 V/cell for this variant.

Adapter input current limiting is enforced by sensing CLP–CLN differential voltage across an external resistor, with ICL pin signaling active limiting. The device lacks built-in termination logic, requiring external MCU supervision for full charge algorithms including C/10 detection, thermal foldback, and safety cutoffs.

Key Specifications

Pinout & Package

Thermally enhanced 20-pin (4 mm × 4 mm) plastic QFN package with exposed GND pad (Pin 21) requiring PCB soldering for thermal and electrical integrity. θ_JA = 37°C/W.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar battery charger controller applications.

Compared with BQ24725ARHBT and MP2759GQZ, the LTC4009CUF-2#TRPBF offers superior analog current monitoring via PROG, flexible discrete current limiting with CLP/CLN, and pin-selectable 4.2 V/cell without firmware dependency - making it ideal for MCU-managed, cost-sensitive, or noise-critical industrial chargers.

Availability

LTC4009CUF-2#TRPBF is available at Aetrix Electronics and suitable for notebook computers, portable instruments, and battery backup systems requiring stable component supply, commercial-temperature grade reliability, and long-term production continuity.

Supply support for LTC4009CUF-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 ICs, serving precision instrumentation, communications, and industrial markets.

The LTC4009 family was designed as a flexible, high-accuracy battery charger controller platform for multi-chemistry, MCU-supervised charging in space-constrained portable equipment - emphasizing low-noise operation, wide input range, and robust status signaling.

FAQ

What battery chemistries does the LTC4009CUF-2#TRPBF support?

The LTC4009CUF-2#TRPBF supports lithium-ion and lithium-polymer battery packs with 1–4 series cells, configured for 4.2 V/cell output via FVS0/FVS1 pins. As a controller (not a complete charger), it requires external MCU supervision for full charge algorithms and can be adapted to other chemistries like LiFePO₄ or NiMH through custom voltage/current profiles and termination logic implemented externally. The LTC4009CUF-2#TRPBF itself does not embed chemistry-specific termination.

How is the 4.2 V/cell output set on the LTC4009CUF-2#TRPBF?

The LTC4009CUF-2#TRPBF uses digital pin-strapping: FVS0 = GND and FVS1 = INTVDD selects the 4.2 V/cell preset output voltage. This eliminates the need for external resistor dividers used in the base LTC4009 variant. The selected voltage is internally generated with ±0.5% accuracy across temperature, and no additional programming components are required for standard Li-ion applications.

Does the LTC4009CUF-2#TRPBF include built-in charge termination?

No, the LTC4009CUF-2#TRPBF does not include built-in charge termination. It is a controller IC that provides precise constant-current and constant-voltage regulation but relies on an external microcontroller to implement full charge algorithms - including C/10 detection (signaled via CHRG pin), thermal cutoff, timer-based termination, and safety timeouts. This architecture gives designers full flexibility for multi-stage or chemistry-specific charging.

What is the function of the PROG pin on the LTC4009CUF-2#TRPBF?

The PROG pin on the LTC4009CUF-2#TRPBF serves two functions: (1) it programs maximum charge current via an external resistor to GND, and (2) it provides a linear analog voltage output (0–1.2 V) proportional to actual charge current - enabling real-time current monitoring without additional sensing circuitry. This dual role simplifies system-level current measurement and closed-loop control in MCU-based designs.

Can the LTC4009CUF-2#TRPBF operate without an external microcontroller?

The LTC4009CUF-2#TRPBF can regulate charge current and voltage autonomously but cannot complete a safe, standards-compliant charge cycle without external supervision. It lacks built-in termination, temperature monitoring, fault recovery, or safety timers. An external microcontroller is required to interpret CHRG/ICL/ACP signals, manage C/10 detection, enforce safety limits, and initiate shutdown - making the LTC4009CUF-2#TRPBF a building-block controller, not a standalone charger.