Analog Devices Inc. LTC4009IUF-2#TRPBF

Overview

LTC4009IUF-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 550 kHz quasi-constant-frequency PWM to eliminate audible noise with ceramic capacitors. It is used in notebook computers and portable instruments requiring high-efficiency, externally managed charging.

For engineers reviewing the LTC4009IUF-2#TRPBF datasheet, LTC4009IUF-2#TRPBF pinout, LTC4009IUF-2#TRPBF application, or LTC4009IUF-2#TRPBF equivalent, key selection criteria include its I-grade temperature range (–40°C to 125°C), 20-pin 4 mm × 4 mm QFN package, AC adapter input current limiting with 3% accuracy, analog charge current monitoring via PROG pin, and absence of built-in termination - requiring external MCU supervision for full charge algorithm control.

Technical Context

The LTC4009IUF-2#TRPBF implements a current-mode synchronous buck topology with fixed 550 kHz nominal switching frequency and adjustable duty cycle up to 99%. Its error amplifier compares a 1.2085 V internal reference against feedback from either an external resistor divider (LTC4009) or digital FVS0/FVS1 pins (LTC4009-2), enabling precise CV regulation.

It integrates dual gate drivers (TGATE and BGATE), a 5 V INTVDD regulator, and three open-drain status outputs (CHRG, ACP, ICL) with defined logic states for bulk charge, C/10 detection, and input current limiting. Charge current is set by RSENSE, RIN, and RPROG; input current limit is set by CLP–CLN differential voltage (100 mV threshold).

Key Specifications

Pinout & Package

20-pin (4 mm × 4 mm) plastic QFN package with exposed thermal pad (Pin 21 = GND), rated for –40°C to 125°C operation. Thermal resistance 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 LTC4009IUF-2#TRPBF, the LTC4009IUF-1#TRPBF offers identical form-factor and thermal performance but targets 4.1 V/cell Li-ion, while the BQ24725ARHBT adds integrated telemetry and safety logic at the cost of larger footprint and non-compatible interface - making LTC4009IUF-2#TRPBF optimal for MCU-supervised, cost-sensitive, high-efficiency designs.

Availability

LTC4009IUF-2#TRPBF is available at Aetrix Electronics and suitable for notebook computers, portable instruments, and battery backup systems requiring stable component supply across industrial temperature ranges and long production lifecycles.

Supply support for LTC4009IUF-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, Inc. (ADI) is a global semiconductor leader specializing in high-performance analog, mixed-signal, and power management ICs for precision, reliability, and efficiency-critical applications.

The LTC4009 product line delivers flexible, high-efficiency battery charger controllers for multi-cell Li-ion/polymer systems, designed for integration into MCU-managed charging architectures where external algorithm control and thermal robustness are essential.

FAQ

What battery chemistries does the LTC4009IUF-2#TRPBF support?

The LTC4009IUF-2#TRPBF supports lithium-ion and lithium-polymer battery packs with 1–4 series cells, configured for 4.2 V/cell float voltage. It does not include built-in charge termination, so external circuitry (e.g., microcontroller) must implement full CC/CV/taper/stop algorithms for any chemistry - including NiMH or lead-acid - provided voltage and current limits are appropriately programmed.

How is the 4.2 V/cell output voltage selected on the LTC4009IUF-2#TRPBF?

The LTC4009IUF-2#TRPBF uses two digital inputs - FVS0 (Pin 9) and FVS1 (Pin 10) - to select its fixed output voltage. For 4.2 V/cell operation, FVS0 = INTVDD (5 V) and FVS1 = INTVDD (5 V). This configuration is hardwired in the device variant; no external resistors are needed, unlike the base LTC4009 which requires an external FBDIV–VFB divider.

Does the LTC4009IUF-2#TRPBF include built-in charge termination?

No, the LTC4009IUF-2#TRPBF does not include built-in charge termination. It is a controller-only IC requiring external supervision (e.g., MCU) to manage end-of-charge conditions such as timer cutoff, voltage plateau detection, or temperature-based termination. The CHRG pin provides C/10 indication but does not autonomously stop charging.

What is the purpose of the ICL pin on the LTC4009IUF-2#TRPBF?

The ICL pin on the LTC4009IUF-2#TRPBF is an active-low open-drain indicator that asserts (pulls low) when the programmed AC adapter input current limit is reached and the charge current is reduced to maintain that limit. It enables system firmware to dynamically adjust load or throttle CPU activity to avoid adapter overload, ensuring stable operation during concurrent charging and system use.

Can the LTC4009IUF-2#TRPBF operate without an external microcontroller?

The LTC4009IUF-2#TRPBF can regulate voltage and current autonomously but cannot complete a safe, standards-compliant charge cycle without external control. Since it lacks built-in termination, thermal monitoring, or safety timers, a microcontroller or dedicated state machine is required to interpret CHRG, ACP, and ICL signals and execute the full charge algorithm - making standalone operation unsafe for production Li-ion systems.