Analog Devices Inc. LT3971EMSE-3.3#TRPBF

Overview

LT3971EMSE-3.3#TRPBF from Analog Devices (formerly Linear Technology) is a fixed 3.3V, 1.2A monolithic buck switching regulator in a 10-lead MSOP package with exposed pad. It operates from 4.3V to 38V input, delivers ultralow 2.8µA quiescent current in regulation, and features low-ripple Burst Mode® operation (<15mV_P-P) for battery-powered industrial sensors and automotive body electronics.

For engineers reviewing the LT3971EMSE-3.3#TRPBF datasheet, LT3971EMSE-3.3#TRPBF pinout, LT3971EMSE-3.3#TRPBF application, or LT3971EMSE-3.3#TRPBF equivalent, key selection criteria include its 3.3V fixed output accuracy (±1.5% over temperature), 700nA shutdown current, power good flag, soft-start capability, and thermal performance in the thermally enhanced MSOP package.

Technical Context

The LT3971EMSE-3.3#TRPBF implements constant-frequency current-mode control with internal compensation, enabling fast transient response and stable loop behavior across wide input and load ranges. Its architecture integrates a 0.33Ω bipolar NPN switch, on-chip boost Schottky diode driver, and accurate 1.19V reference for feedback regulation.

Burst Mode® operation reduces no-load supply current to 2.8µA while maintaining output ripple below 15mV_P-P; frequency foldback during startup and overload protects against excessive inductor current. The power good (PG) flag asserts when VOUT reaches 91% of nominal, and the EN pin features 1.01V rising threshold with 30mV hysteresis.

Key Specifications

Pinout & Package

LT3971EMSE-3.3#TRPBF uses a 10-lead plastic MSOP package (3mm × 3mm footprint) with exposed pad (Pin 11) soldered to PCB for low thermal resistance (θ_JA = 45°C/W).

Key Features

Applications

Equivalent & Alternatives

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

Compared with LMR36520RNXR and TPS62840DGRR, the LT3971EMSE-3.3#TRPBF uniquely balances 38V input tolerance, 1.2A capability, 2.8µA IQ, and compact MSOP packaging - making it optimal for space- and reliability-critical 12V/24V embedded systems where both wide VIN and low standby power are mandatory.

Availability

LT3971EMSE-3.3#TRPBF is available at Aetrix Electronics and suitable for automotive body electronics, industrial wireless sensors, portable medical diagnostics, and rail-to-rail PLC I/O modules requiring stable component supply with long-term lifecycle assurance.

Supply support for LT3971EMSE-3.3#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 and power management portfolio for demanding industrial and automotive applications.

The LT3971 family was designed specifically for high-input-voltage, ultralow-quiescent-current buck conversion in battery-backed and automotive systems where efficiency at µA loads and robustness across wide temperature ranges are critical.

FAQ

What is the guaranteed output voltage accuracy of the LT3971EMSE-3.3#TRPBF over temperature?

The LT3971EMSE-3.3#TRPBF guarantees a 3.3V output within ±1.5% (3.25V to 3.35V) across its full operating junction temperature range of –40°C to 125°C, as confirmed by electrical characterization in the datasheet's "LT3971-3.3 Output Voltage" specification table. This accuracy holds under all line and load conditions within rated specifications and does not require external trimming components due to its internal 10MΩ feedback divider.

Can the LT3971EMSE-3.3#TRPBF operate with input voltages below 4.3V?

No - the LT3971EMSE-3.3#TRPBF has a minimum input voltage of 4.3V for proper regulation, as specified in the Absolute Maximum Ratings and Electrical Characteristics tables. Below this threshold, the internal circuitry cannot maintain feedback control or sustain switch operation; attempting to operate below 4.3V may result in unregulated output or dropout. For sub-4.3V applications, an alternative regulator such as the LT8610 (3.0V min VIN) should be evaluated.

How does the LT3971EMSE-3.3#TRPBF achieve 2.8µA quiescent current while regulating?

The LT3971EMSE-3.3#TRPBF achieves 2.8µA quiescent current through patented low-ripple Burst Mode® operation: during light loads, it delivers discrete current pulses to the output capacitor and enters deep sleep between bursts, powering down oscillator, error amplifier, and gate drive circuitry. This architecture - combined with optimized bias networks and a high-impedance internal feedback divider - reduces total input current to 2.8µA while maintaining regulation and <15mV_P-P ripple in typical applications.

Is an external catch diode required when using the LT3971EMSE-3.3#TRPBF?

Yes - the LT3971EMSE-3.3#TRPBF requires an external Schottky diode connected between the SW pin and VOUT. Although it integrates a boost Schottky diode driver (BD pin) and internal switch, the catch diode itself is external to enable selection of low-leakage, high-speed devices (e.g., <1µA reverse leakage at 25°C) critical for achieving ultralow quiescent current. The datasheet specifies DFLS2100 as a recommended part.

What is the function of the SYNC pin on the LT3971EMSE-3.3#TRPBF, and how should it be configured?

The SYNC pin on the LT3971EMSE-3.3#TRPBF selects between low-ripple Burst Mode® (SYNC grounded) and external clock synchronization (SYNC tied to 250kHz–2MHz square wave). Grounding SYNC enables optimal light-load efficiency (2.8µA IQ); connecting to an external clock forces pulse-skipping mode, increasing IQ to 1.5mA. For most battery-powered applications, SYNC must be grounded - tying it high offers no benefit and is not recommended.