Analog Devices Inc. LT3971AIMSE-5#TRPBF

Overview

LT3971AIMSE-5#TRPBF from Analog Devices (formerly Linear Technology) is a fixed-output 5.0V, 1.3A monolithic buck switching regulator in a thermally enhanced 10-lead MSOP package with exposed pad. It operates from 4.3V to 38V input, delivers ultralow 2.2μA quiescent current at no load (12V_IN→5V_OUT), features low-ripple Burst Mode operation (<15mV_P-P), and integrates power good flag, soft-start, and internal 10MΩ feedback divider optimized for USB VBUS regulation.

For engineers reviewing the LT3971AIMSE-5#TRPBF datasheet, LT3971AIMSE-5#TRPBF pinout, LT3971AIMSE-5#TRPBF application, or LT3971AIMSE-5#TRPBF equivalent, key selection criteria include its guaranteed 5.0V ±1.2% output accuracy over temperature, specified V_OUT pin current (–0.5μA typ), ABSMAX current compliance, and USB-specific PG threshold offset (9% of V_OUT).

Technical Context

The LT3971AIMSE-5#TRPBF implements a constant-frequency, current-mode control architecture with internal compensation and a bipolar NPN main switch (0.33Ω R_DS(on) equiv). Its fixed 5V output is regulated via an integrated 10MΩ resistor divider connected to the V_OUT pin-eliminating external FB resistors while maintaining ±0.6% initial accuracy and <0.01%/V line regulation.

Burst Mode operation is enabled by grounding the SYNC pin, reducing no-load input current to 2.2μA while holding output ripple below 15mV_P-P; power good signaling occurs when V_OUT reaches 91% of regulation, with 1.3% hysteresis. The device supports frequency synchronization from 250kHz to 2MHz via the RT pin but requires SYNC grounded for ultralow-I_Q operation.

Key Specifications

Pinout & Package

LT3971AIMSE-5#TRPBF is housed in a 10-lead MSOP package (MSE) with exposed thermal pad (Pin 11 = GND), θ_JA = 45°C/W, θ_JC = 10°C/W. The exposed pad must be soldered to PCB for thermal performance and EMI reduction.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar fixed-output buck regulator applications.

Compared with LT3971IMSE-5#TRPBF, the LT3971AIMSE-5#TRPBF provides tighter 5V accuracy (±1.2% vs ±2%), lower I_Q (2.2μA vs 3.5μA), and USB-specific validation; versus TPS54302DDCR, it delivers plug-and-play 5V USB compliance without external resistors or PG circuitry.

Availability

LT3971AIMSE-5#TRPBF is available at Aetrix Electronics and suitable for automotive USB charging ports, industrial sensor nodes, and portable medical devices requiring stable component supply with guaranteed long-term availability.

Supply support for LT3971AIMSE-5#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 its high-performance power management portfolio with rigorous automotive and industrial qualification standards.

The LT3971A family was designed specifically for wide-input, ultralow-I_Q buck regulation in battery-backed and automotive systems-emphasizing USB compliance, thermal robustness, and seamless integration into space-constrained designs.

FAQ

What is the guaranteed output voltage accuracy of the LT3971AIMSE-5#TRPBF over temperature?

The LT3971AIMSE-5#TRPBF guarantees 5.00V output with ±1.2% accuracy across the full –40°C to 125°C junction temperature range, as confirmed by electrical characteristics tables in the official datasheet. This specification includes initial tolerance, line regulation, and temperature drift-making it suitable for USB VBUS applications where strict 4.75V–5.25V compliance is mandatory. The LT3971AIMSE-5#TRPBF achieves this via laser-trimmed internal 10MΩ feedback resistors and process-matched reference circuitry.

Can the LT3971AIMSE-5#TRPBF be used for 5.15V USB VBUS regulation, and how is it configured?

Yes, the LT3971AIMSE-5#TRPBF supports 5.15V USB VBUS regulation by adding two external 1% resistors to the VOUT pin, as shown in Figure 3 of the datasheet. The internal 10MΩ divider sets the base 5V output, and the external network scales it upward while preserving accuracy-since the external resistors dominate the divider current, minimizing error from the VOUT pin's ±0.5μA current. This configuration ensures the LT3971AIMSE-5#TRPBF meets USB specification margins after cable drop.

What is the minimum input voltage required for the LT3971AIMSE-5#TRPBF to regulate 5V output?

The LT3971AIMSE-5#TRPBF requires a minimum input voltage of 4.3V to initiate regulation, as specified in Absolute Maximum Ratings and Electrical Characteristics. Below this, the internal circuitry cannot bias up; above it, regulation is maintained across the full 4.3V–38V range. At light loads and high frequencies, dropout may increase slightly due to minimum on-time limits-but the LT3971AIMSE-5#TRPBF reliably starts and regulates from 4.3V at 5V output under all conditions.

How does the LT3971AIMSE-5#TRPBF achieve 2.2μA quiescent current, and what conditions are required?

The LT3971AIMSE-5#TRPBF achieves 2.2μA quiescent current by entering low-ripple Burst Mode operation, which shuts down non-essential circuitry between switching pulses. This requires the SYNC pin to be grounded (not floating or driven), VIN ≥ 4.3V, and light load conditions (<92mA). Under these conditions, the LT3971AIMSE-5#TRPBF delivers single current pulses to maintain VOUT while sleeping between them-reducing average input current to 2.2μA at 12VIN→5VOUT.

Does the LT3971AIMSE-5#TRPBF require external compensation components?

No, the LT3971AIMSE-5#TRPBF uses an internally compensated current-mode control architecture, eliminating the need for external compensation networks. The internal compensation is optimized for stability with standard output capacitor ESR ranges and inductor values recommended in the datasheet (e.g., 10μH for 400kHz operation). This simplifies design, reduces BOM count, and ensures robust transient response without loop tuning-key for rapid deployment in USB and industrial applications.