Analog Devices Inc. LT1571EGN-5#PBF

Overview

LT1571EGN-5#PBF from Analog Devices (formerly Linear Technology) is a 500kHz fixed-output constant-current/constant-voltage PWM battery charger IC for single-cell Li-Ion batteries, delivering up to 1.5A DC charge current with 4.1V or 4.2V preset output voltage (±0.6% accuracy), internal 0.1Ω sense resistor, and open-collector FLAG output for charge termination detection in portable power systems.

For engineers reviewing the LT1571EGN-5#PBF datasheet, LT1571EGN-5#PBF pinout, LT1571EGN-5#PBF application, or LT1571EGN-5#PBF equivalent, key selection criteria include switching frequency (500kHz), fixed 4.1V/4.2V cell voltage option, 16-pin narrow SSOP thermal package, charge current programming via PROG pin, and FLAG-based end-of-charge signaling in compact Li-Ion charging designs.

Technical Context

The LT1571EGN-5#PBF implements a current-mode PWM buck topology with integrated NPN power switch (2A peak), BOOST-driven saturation control, and dual-loop regulation: inner current loop via CA1/CA2 amplifiers sensing across internal 0.1Ω resistor, outer voltage loop using 2.465V ±0.6% reference and BAT2 pin for Kelvin-sensed battery voltage feedback.

It operates exclusively at 500kHz (440–550kHz over temperature), supports 4.1V/4.2V cell voltage selection via SELECT pin logic (open = 4.1V, grounded = 4.2V), and enters low-drain sleep mode (<5µA) when input power is removed - enabling cradle and adapter-based charging without battery drain.

Key Specifications

Pinout & Package

LT1571EGN-5#PBF is housed in a 16-lead narrow plastic SSOP (GN package) with fused GND pins connected to internal die attach paddle for heat sinking. Four corner GND pins must be soldered to expanded PCB lands for thermal performance.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LTC4000-5#PBF and BQ24075RGTR, LT1571EGN-5#PBF offers the most direct solution for compact, cost-sensitive 500kHz adapter-fed single-cell Li-Ion chargers with factory-preset 4.1V/4.2V outputs and minimal external components - balancing integration, accuracy, and thermal performance in 16-pin SSOP.

Availability

LT1571EGN-5#PBF is available at Aetrix Electronics and suitable for smartphone battery charging, wearable cradle chargers, portable medical instrument power, and industrial handheld scanner battery packs requiring stable component supply and long-term manufacturability.

Supply support for LT1571EGN-5#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 its precision analog and power management portfolio, emphasizing high-performance, thermally robust ICs for demanding industrial and portable applications.

The LT1571 series belongs to Linear Technology's dedicated battery charger IC product line, designed specifically for efficient, accurate, and autonomous constant-current/constant-voltage charging of Li-Ion, NiMH, and NiCd batteries in space- and thermal-constrained systems.

FAQ

What is the switching frequency of the LT1571EGN-5#PBF and how does it affect design?

The LT1571EGN-5#PBF operates at a fixed 500kHz switching frequency (440–550kHz over temperature). This allows use of smaller inductors (e.g., 10µH) and lower-value input/output capacitors compared to 200kHz variants like LT1571EGN-1, reducing board area and improving transient response in compact portable chargers. The higher frequency also increases switching losses slightly, requiring attention to thermal layout at >1A loads.

How is the battery voltage set on the LT1571EGN-5#PBF?

The LT1571EGN-5#PBF has factory-preset battery voltage options: 4.1V (SELECT pin left open) or 4.2V (SELECT pin grounded). Unlike the adjustable LT1571EGN-1, it contains internal resistor dividers tied to the BAT2 pin, eliminating external feedback components and ensuring ±0.6% accuracy without resistor tolerance or temperature drift effects.

What does the FLAG pin on the LT1571EGN-5#PBF indicate and how is it used?

The FLAG pin on the LT1571EGN-5#PBF is an open-collector output that goes low when the charge current drops to ≤20% of the programmed maximum (e.g., ≤200mA for a 1A setup), indicating near-full charge in constant-voltage mode. It requires an external pull-up resistor and can directly trigger a microcontroller interrupt, LED driver, or safety timer to terminate charging or initiate maintenance cycles.

Can the LT1571EGN-5#PBF charge batteries other than single-cell Li-Ion?

Yes - the LT1571EGN-5#PBF supports charging of NiMH and NiCd batteries using constant-current mode only, though its preset 4.1V/4.2V output is optimized for Li-Ion. For non-Li-Ion chemistries, the voltage regulation loop is typically disabled (e.g., by grounding VFB on LT1571EGN-1), but LT1571EGN-5#PBF lacks VFB; thus, it functions best as a precision CC source with external voltage clamping or monitoring.

What thermal considerations apply to the LT1571EGN-5#PBF in high-current operation?

The LT1571EGN-5#PBF uses a 16-pin narrow SSOP package with θ_JA = 75°C/W. At 1.5A charge current and 8.2V input, power dissipation exceeds 1W; proper thermal design - including soldering all four corner GND pins to large copper pours - is essential to keep junction temperature below 125°C. Derating to ≤1.2A is recommended above 60°C ambient without enhanced cooling.