Analog Devices Inc. LTC4009IUF-1#PBF

Overview

LTC4009IUF-1#PBF 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 4.1V/cell, supports 6V–28V input and 2V–28V output ranges, and features programmable charge current (±4% accuracy) and AC adapter input current limiting (±3% accuracy). It enables high-efficiency charging in notebook computers and portable instruments without audible noise using ceramic capacitors.

For engineers reviewing the LTC4009IUF-1#PBF datasheet, LTC4009IUF-1#PBF pinout, LTC4009IUF-1#PBF application, or LTC4009IUF-1#PBF equivalent, key selection considerations include its I-grade (–40°C to 125°C) operation, pin-programmable 4.1V/cell output, synchronous 550kHz PWM architecture, and integrated indicators for AC present, charging status, C/10 detection, and input current limiting.

Technical Context

The LTC4009IUF-1#PBF implements a current-mode synchronous buck topology with quasi-constant 550kHz switching frequency, enabling compact magnetics and ceramic bulk capacitors without audible noise. Its control loop uses ITH as the PWM ramp reference, PROG as the averaged charge current feedback node, and VFB (or FVS0/FVS1 on -1 variant) for precise voltage regulation.

It integrates dual-loop regulation: constant-current mode governed by CSP/CSN sense resistor and RPROG/RIN programming, and constant-voltage mode governed by external feedback (LTC4009) or digital pin-selectable thresholds (LTC4009-1). Input current limiting is enforced via CLP/CLN differential sensing, with ICL output signaling active limiting.

Key Specifications

Pinout & Package

20-pin (4mm × 4mm) plastic QFN package with exposed GND pad (Pin 21), optimized for thermal dissipation and high-density PCB layouts. Pin functions are validated per Linear Technology's official LTC4009-1 datasheet (Rev. D).

Key Features

Applications

Equivalent & Alternatives

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

Compared with LTC4009IUF-2#PBF, the LTC4009IUF-1#PBF provides tighter 4.1V/cell regulation for conservative Li-ion charging, while BQ24725ARGRT adds digital control at the cost of increased firmware complexity and loss of analog PROG monitoring.

Availability

LTC4009IUF-1#PBF is available at Aetrix Electronics and suitable for notebook computers, portable instruments, and battery backup systems requiring stable component supply, extended temperature operation, and precision multi-cell Li-ion charging.

Supply support for LTC4009IUF-1#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 and maintains full technical and manufacturing continuity for the LTC portfolio.

The LTC4009 family is designed as a flexible, high-accuracy battery charger controller platform supporting multi-chemistry charging under external microcontroller supervision - targeting portable computing and industrial portable equipment.

FAQ

What is the exact float voltage output of LTC4009IUF-1#PBF?

The LTC4009IUF-1#PBF is factory-configured to deliver 4.1V per cell for lithium-ion/polymer battery packs with 1–4 series cells. This value is set by internal precision resistors selected via FVS0 and FVS1 pins, eliminating the need for external feedback resistors and ensuring ±0.5% accuracy over –40°C to +125°C.

Does LTC4009IUF-1#PBF include built-in charge termination?

No, the LTC4009IUF-1#PBF does not include built-in charge termination. It is a controller IC intended for use with an external microcontroller or state machine that manages full CC/CV algorithms, including C/10 cutoff, temperature monitoring, and safety timers. The CHRG pin provides C/10 status indication but does not autonomously terminate charge.

How is input current limiting configured on LTC4009IUF-1#PBF?

Input current limiting on LTC4009IUF-1#PBF is configured using an external sense resistor (RIN) between CLP and CLN pins. The threshold is fixed at 100mV differential, so RIN value determines the absolute current limit (ILIM ≈ 100mV / RIN). The ICL pin asserts low when limiting is active, enabling real-time system-level power budgeting.

Can LTC4009IUF-1#PBF operate with ceramic output capacitors without audible noise?

Yes, the LTC4009IUF-1#PBF uses a synchronous quasi-constant frequency PWM architecture operating at 550kHz, which avoids sub-audible switching frequencies. This allows full use of low-ESR ceramic capacitors on both input and output without generating audible noise - a key advantage over variable-frequency or low-frequency controllers.

What is the thermal performance of LTC4009IUF-1#PBF in its QFN package?

The LTC4009IUF-1#PBF uses a thermally enhanced 20-pin 4mm × 4mm QFN with exposed GND pad (Pin 21). Its specified thermal resistance is θJA = 37°C/W with proper PCB copper pour. Junction temperature must remain ≤125°C; design margin requires verifying power dissipation under worst-case load, ambient, and layout conditions.