Analog Devices Inc. LTC3871ILXE

Overview

LTC3871ILXE from Analog Devices is a 4-quadrant, bidirectional synchronous DC/DC controller IC designed for bipolar power supplies that source and sink current across ±10 V output rails. It supports input voltage ranges from 5 V to 24 V, delivers up to 3 A continuous output current, operates at 200 kHz switching frequency, and features integrated gate drivers for N- and P-channel MOSFETs in a 38-pin LQFP package. It enables regenerative braking and audio H-bridge biasing in automotive and precision analog systems.

For engineers reviewing the LTC3871ILXE datasheet, LTC3871ILXE pinout, LTC3871ILXE application, or LTC3871ILXE equivalent, key selection criteria include its 4-quadrant control architecture, dual-sense resistor interface (RS1/RS2), ±10 V programmable output with 0.1 V–1.048 V analog control input, and cold-crank resilient operation down to 5 V input without loss of bidirectional functionality.

Technical Context

The LTC3871ILXE implements true 4-quadrant regulation by independently controlling both sourcing and sinking modes via separate current-sense inputs (ISN/ISP) and dedicated gate drive outputs (TG/BG). Its control loop accepts an external analog voltage (CTRL pin) to linearly set output polarity and magnitude between –10 V and +10 V while maintaining regulation under dynamic load and input transients.

It integrates synchronous rectification logic with phase-aligned gate timing for QN1 and QP1, supports external clock synchronization (SYNC pin), and uses internal charge pump circuitry to sustain gate drive during low-VIN conditions. The device does not integrate power MOSFETs and requires external discrete inductors (L1/L2) and sense resistors for full 4-quadrant operation.

Key Specifications

Pinout & Package

Package: 38-pin LQFP (7 mm × 7 mm), exposed thermal pad, lead-free and RoHS-compliant.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar 4-quadrant controller applications.

Compared with LT8714 and LTC7804, the LTC3871ILXE uniquely combines analog-programmable bipolar output, dual current-sense interface, and cold-crank tolerant 5 V–24 V operation in a single controller-making it the only direct fit for compact, high-fidelity 4-quadrant supply designs where size, simplicity, and transient immunity are critical.

Availability

LTC3871ILXE is available at Aetrix Electronics and suitable for automotive regenerative braking systems, audio amplifier bias supplies, industrial test equipment, and battery emulation platforms requiring stable component supply with guaranteed long-term availability.

Supply support for LTC3871ILXE 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 leader in high-performance analog, mixed-signal, and digital signal processing semiconductors, serving industrial, automotive, communications, and healthcare markets.

The LTC3871ILXE belongs to ADI's Power by Linear™ 4-quadrant controller product line, engineered specifically for bipolar, bidirectional power conversion in safety-critical and high-dynamic-range applications where conventional buck or boost topologies fall short.

FAQ

What is the primary function of the LTC3871ILXE in a power system?

The LTC3871ILXE is a 4-quadrant synchronous DC/DC controller that regulates bipolar output voltages (±10 V) while sourcing and sinking current. Unlike standard buck or boost controllers, the LTC3871ILXE enables true bidirectional power flow-making it essential for applications like regenerative braking and audio biasing where energy must flow both to and from the load. Its analog CTRL input directly maps to output voltage polarity and magnitude.

Does the LTC3871ILXE integrate power MOSFETs or require external ones?

The LTC3871ILXE does not integrate power MOSFETs and requires external N-channel (QN1) and P-channel (QP1) MOSFETs for full 4-quadrant operation. It provides dedicated TG and BG gate drivers with matched timing to ensure synchronous rectification and minimize conduction losses. Reference designs validate use of BSC034N06NS and SQJ457EP-T1 GE3 MOSFETs with the LTC3871ILXE.

Can the LTC3871ILXE operate during automotive cold-crank conditions?

Yes, the LTC3871ILXE is explicitly designed for cold-crank resilience, supporting continuous 4-quadrant operation across a 5 V to 24 V input range. During input drops to 5 V, it maintains regulation of ±10 V output without mode switching or loss of sinking capability-verified in bench testing with 4.5 A reverse current at 12.5 V input. This makes the LTC3871ILXE suitable for automotive start-stop and battery transient environments.

How is output voltage polarity and magnitude controlled on the LTC3871ILXE?

Output voltage is controlled via the analog CTRL pin, which accepts a 0.1 V to 1.048 V input signal. At 0.1 V, the LTC3871ILXE regulates –10 V; at 1.048 V, it regulates +10 V. This linear mapping enables smooth zero-crossing transitions-demonstrated with 60 Hz sine-wave output in application circuits. No DAC, microcontroller, or digital interface is required to program the LTC3871ILXE.

What are the key thermal considerations for the LTC3871ILXE in bidirectional operation?

The LTC3871ILXE uses a 38-pin LQFP package with an exposed thermal pad rated for operation up to +125°C junction temperature. Thermal imaging confirms stable operation at 4.5 A reverse current (sink mode) with peak temperatures below 45°C on the power train. Proper PCB copper pour under the exposed pad and thermal vias to inner ground planes are required to maintain reliability in sustained 3 A sourcing or sinking conditions.