Analog Devices Inc. LT3971EMSE-5#TRPBF

Overview

LT3971EMSE-5#TRPBF from Analog Devices (formerly Linear Technology) is a fixed-output 5V, 1.2A monolithic buck switching regulator in a 10-lead MSOP package. It operates from 4.3V to 38V input, delivers ultralow 2.8µA quiescent current in regulation, maintains <15mV_P-P output ripple via low-ripple Burst Mode®, and integrates a 0.33Ω switch, boost Schottky diode, and internal compensation. It is used in automotive battery-powered systems requiring long standby life.

For engineers reviewing the LT3971EMSE-5#TRPBF datasheet, LT3971EMSE-5#TRPBF pinout, LT3971EMSE-5#TRPBF application, or LT3971EMSE-5#TRPBF equivalent, key selection criteria include its 5V fixed output, 2.8µA no-load IQ, 38V max VIN tolerance, power good flag, and soft-start capability - all critical for low-power industrial and automotive supply designs.

Technical Context

The LT3971EMSE-5#TRPBF implements constant-frequency current-mode control with adjustable switching frequency (200kHz–2MHz) set by an external RT resistor. Its internal 10MΩ feedback divider fixes VOUT to 5.00V ±1.4% over temperature and line, eliminating external resistors.

Burst Mode® operation reduces input current to 1.7µA in sleep cycles while maintaining tight output regulation and sub-15mV ripple; synchronization via the SYNC pin disables Burst Mode and increases light-load IQ to 1.5mA. The device features an accurate 1.01V enable threshold with 30mV hysteresis and a power good flag asserting when VOUT reaches 91% of nominal.

Key Specifications

Pinout & Package

LT3971EMSE-5#TRPBF is housed in a thermally enhanced 10-lead plastic MSOP package (3mm × 3mm footprint) with exposed pad (Pin 11) soldered to PCB ground for low θ_JA = 45°C/W.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LMR36520RNXR and TPS62840DGRR, the LT3971EMSE-5#TRPBF uniquely balances 38V input tolerance, 5V fixed output, 2.8µA IQ, and integrated power good - making it irreplaceable in automotive and wide-input industrial 5V rail designs where all four attributes are simultaneously required.

Availability

LT3971EMSE-5#TRPBF is available at Aetrix Electronics and suitable for automotive body electronics, industrial sensor transmitters, portable medical monitors, and smart building occupancy sensors requiring stable component supply across extended temperature ranges (–40°C to 125°C).

Supply support for LT3971EMSE-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-reliability analog power portfolio with rigorous qualification and long-term product support.

The LT3971 family was designed specifically for ultralow-quiescent-current step-down regulation in automotive, industrial, and battery-critical applications where extended standby life and wide input voltage range are essential.

FAQ

What is the guaranteed output voltage accuracy of the LT3971EMSE-5#TRPBF over temperature?

The LT3971EMSE-5#TRPBF guarantees 5.00V output with ±1.4% total error over –40°C to 125°C junction temperature, including initial tolerance, line regulation, and load regulation. This is achieved via laser-trimmed internal 10MΩ feedback resistors and a precision 1.19V reference, eliminating external resistor drift and leakage errors that degrade accuracy in adjustable regulators.

Does the LT3971EMSE-5#TRPBF require an external catch diode?

Yes, the LT3971EMSE-5#TRPBF requires an external Schottky catch diode connected between SW and VOUT. Although it integrates a boost Schottky diode (between BD and BOOST), the main power path relies on an external diode for inductor freewheeling. A low-leakage (<1µA), low-V_F Schottky such as DFLS2100 is recommended to preserve ultralow quiescent current performance.

How does the LT3971EMSE-5#TRPBF achieve 2.8µA quiescent current while regulating?

The LT3971EMSE-5#TRPBF achieves 2.8µA quiescent current through low-ripple Burst Mode® operation: it delivers discrete current pulses to the output capacitor, then enters deep sleep (drawing only 1.7µA), minimizing average input current. The internal oscillator, error amplifier, and gate driver are fully disabled between bursts, while the 1.19V reference and PG comparator remain active to monitor regulation status.

Can the LT3971EMSE-5#TRPBF be synchronized to an external clock?

Yes, the LT3971EMSE-5#TRPBF can be synchronized using the SYNC pin. When driven by an external clock (250kHz–2MHz), it locks its switching frequency and phase but exits Burst Mode, increasing light-load quiescent current to ~1.5mA. For lowest IQ, SYNC must be grounded; for EMI reduction in noise-sensitive systems, external sync is viable with the IQ trade-off accepted.

What thermal design considerations apply to the LT3971EMSE-5#TRPBF in MSOP package?

The LT3971EMSE-5#TRPBF's 10-lead MSOP package features an exposed thermal pad (Pin 11) that must be soldered to a minimum 100mm² copper pour tied to GND for effective heat dissipation. With θ_JA = 45°C/W, continuous 1.2A operation at 36V_IN/5V_OUT requires ≤40°C ambient or forced airflow to maintain <125°C junction temperature; thermal vias under the pad are strongly recommended.