Analog Devices Inc. LT1571EGN-2#TRPBF

Overview

LT1571EGN-2#TRPBF from Analog Devices (formerly Linear Technology) is a 200kHz fixed-output constant-current/constant-voltage battery charger IC for Li-Ion, NiMH, and NiCd batteries. It delivers up to 1.5A DC charge current with 5% accuracy, features an internal 0.1Ω sense resistor, supports preset 8.2V/8.4V output via SELECT pin, and provides a FLAG signal at 20% current taper for Li-Ion charge termination - used in compact cradle chargers and portable instrumentation.

For engineers reviewing the LT1571EGN-2#TRPBF datasheet, LT1571EGN-2#TRPBF pinout, LT1571EGN-2#TRPBF application, or LT1571EGN-2#TRPBF equivalent, key selection criteria include its 28-pin SSOP package thermal performance (θJA = 40°C/W), 8.2V/8.4V fixed voltage options, 200kHz switching frequency, integrated current-sense amplifier, and open-collector FLAG output for end-of-charge detection in space-constrained battery-powered systems.

Technical Context

The LT1571EGN-2#TRPBF implements a current-mode PWM buck topology with internal NPN power switch and bootstrap-driven BOOST pin. Its dual-loop control uses CA1 for precise current regulation (via SENSE/BAT pins and 0.1Ω internal sense resistor) and VA amplifier for voltage regulation against a 2.465V ±0.5% reference, enabling seamless CC/CV transition during Li-Ion charging.

It integrates dedicated circuitry for battery protection: undervoltage lockout (7V typical), reverse-battery drain suppression (5µA sleep current), and programmable charge termination via CAP/FLAG interface. The 28-pin fused-lead SSOP package thermally couples four corner GND pins to the die attach paddle for enhanced heat dissipation in high-current applications.

Key Specifications

Pinout & Package

LT1571EGN-2#TRPBF is housed in a 28-lead narrow plastic SSOP (GN) package with fused lead construction. Four corner GND pins are internally connected to the die attach paddle for thermal conduction; PCB land patterns must expand these pads for effective heat sinking. Absolute max VCC = 28 V, BOOST–VCC ≤ 20 V, FLAG ≤ VCC.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LTC4000-1#PBF and BQ24610RGER, LT1571EGN-2#TRPBF offers plug-and-play 8.2V/8.4V charging with no external sense resistor or digital interface - reducing BOM count and layout complexity for cost-sensitive, fixed-output portable chargers.

Availability

LT1571EGN-2#TRPBF is available at Aetrix Electronics and suitable for smartphone cradle chargers, portable medical monitors, industrial handheld scanners, and wearable docking stations requiring stable component supply and long-term production continuity.

Supply support for LT1571EGN-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 and maintains full support for legacy Linear power management products including the LT1571 family.

The LT1571 product line was designed specifically for high-efficiency, low-component-count battery charging in space-constrained portable electronics - emphasizing integrated sensing, fixed-voltage presets, and robust thermal packaging for 1A+ applications.

FAQ

What battery chemistries does the LT1571EGN-2#TRPBF support?

The LT1571EGN-2#TRPBF supports lithium-ion (Li-Ion), nickel-metal-hydride (NiMH), and nickel-cadmium (NiCd) batteries. Its constant-current/constant-voltage architecture is optimized for Li-Ion 2-cell packs (8.2V/8.4V), while its wide 1V–20V battery voltage range and programmable current make it adaptable to NiMH/NiCd configurations with appropriate termination methods like –dV/dt or temperature sensing. The LT1571EGN-2#TRPBF does not support lead-acid or LiFePO₄ without external voltage scaling.

How is the 8.2V/8.4V output voltage selected on the LT1571EGN-2#TRPBF?

The LT1571EGN-2#TRPBF uses the SELECT pin to choose between two factory-trimmed output voltages: leaving SELECT floating configures 8.2V, while grounding SELECT selects 8.4V. This hardware-based selection requires no external resistors or configuration registers. The internal voltage divider connects to BAT2, and an integrated switch disconnects it during shutdown to eliminate parasitic drain - a feature confirmed in the LT1571EGN-2#TRPBF datasheet's "BAT2 Pin" description and Figure 7 application circuit.

What is the function of the FLAG pin on the LT1571EGN-2#TRPBF?

The FLAG pin on the LT1571EGN-2#TRPBF is an open-collector output that signals near-full charge by pulling low when battery charge current drops to 20% of the programmed value - a threshold set by comparator E6 monitoring the CAP pin's filtered current signal. It sinks ≥1 mA and requires an external pull-up resistor. This signal is used to trigger external timers or microcontroller interrupts for charge termination. The LT1571EGN-2#TRPBF allows adjustment of this threshold down to 7.5% using an RCAP resistor on the CAP pin.

Can the LT1571EGN-2#TRPBF operate without an external current-sense resistor?

Yes, the LT1571EGN-2#TRPBF operates without an external current-sense resistor because it integrates a precision 0.1Ω metal-strip sense element between the SENSE and BAT pins. Charge current is programmed by setting the PROG pin current (IPROG = IBAT/2000) using a single external resistor to ground - for example, 4.93kΩ yields 1A. This eliminates board space, cost, and tolerance errors associated with discrete sense resistors, and is explicitly documented in the LT1571EGN-2#TRPBF's "Features" and "Charge Current Programming" sections.

What thermal design considerations apply to the LT1571EGN-2#TRPBF in high-current operation?

The LT1571EGN-2#TRPBF uses a 28-pin SSOP package with four corner GND pins fused to the internal die attach paddle for thermal conduction. To maintain junction temperature ≤125°C at 1.5A, PCB land patterns must expand these GND pads into a thermal plane - achieving the specified 40°C/W θJA. Layout guidelines require short, wide traces to SW/GND, placement of input/output capacitors near respective pins, and avoidance of routing under the IC body. These requirements are detailed in the LT1571EGN-2#TRPBF's "Package Information" and "Thermal Calculations" sections.