Analog Devices Inc. LT3971EDD-3.3#PBF

Overview

LT3971EDD-3.3#PBF from Analog Devices (formerly Linear Technology) is a fixed-output 3.3V, 1.2A monolithic buck switching regulator in a thermally enhanced 10-lead (3mm × 3mm) DFN 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 power switch, boost Schottky diode, and internal compensation - ideal for automotive battery-powered systems requiring long standby life.

For engineers reviewing the LT3971EDD-3.3#PBF datasheet, LT3971EDD-3.3#PBF pinout, LT3971EDD-3.3#PBF application, or LT3971EDD-3.3#PBF equivalent, key selection criteria include its fixed 3.3V output, 2.8µA no-load IQ, 1.2A output capability, 4.3–38V input range, and integrated soft-start and power-good flag - all critical for low-power industrial and automotive DC/DC conversion.

Technical Context

The LT3971EDD-3.3#PBF employs a constant-frequency current-mode control architecture with internal 10MΩ feedback divider set for 3.3V output (±1.5% over temperature). Its oscillator supports 200kHz–2MHz operation via RT resistor or external sync, and features frequency foldback during startup/overload to limit inrush and sustain regulation.

Burst Mode® operation enables ultralow IQ by disabling control circuitry between energy pulses while maintaining tight output regulation; the open-drain PG pin asserts when VOUT reaches 91% of nominal, and the EN pin provides 1.01V rising threshold with 30mV hysteresis for precise enable/disable control.

Key Specifications

Pinout & Package

LT3971EDD-3.3#PBF uses a 10-lead (3mm × 3mm) plastic DFN package with exposed thermal pad (Pin 11 = GND), optimized for low θ_JA = 45°C/W and high power density.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LMR36520RNXR and TPS62840DRVR, the LT3971EDD-3.3#PBF uniquely balances 38V input capability, 2.8µA IQ, integrated PG/SS, and automotive-grade thermal performance in a 3mm × 3mm footprint - making it optimal for battery-backed industrial and automotive systems demanding both longevity and ruggedness.

Availability

LT3971EDD-3.3#PBF is available at Aetrix Electronics and suitable for automotive body control modules, industrial sensor nodes, portable medical diagnostics, and rail-to-rail PLC I/O modules requiring stable component supply across extended temperature and long product lifecycles.

Supply support for LT3971EDD-3.3#PBF 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 power management semiconductors, formed through the acquisition of Linear Technology in 2017.

The LT3971 family was designed by Linear Technology specifically for high-input-voltage, ultralow-quiescent-current DC/DC conversion in automotive, industrial, and battery-powered applications - emphasizing reliability, thermal efficiency, and ease of use without external compensation.

FAQ

What is the guaranteed output voltage accuracy of the LT3971EDD-3.3#PBF over temperature?

The LT3971EDD-3.3#PBF guarantees a 3.3V output with ±1.5% tolerance over the full –40°C to 125°C junction temperature range, as confirmed by electrical characterization data in the datasheet (Section "ELECTRICAL CHARACTERISTICS", row "LT3971-3.3 Output Voltage"). This accuracy is achieved using an internal precision 10MΩ feedback divider and trimmed bandgap reference, eliminating drift-related errors common in external resistor networks.

Can the LT3971EDD-3.3#PBF operate from a 5V input source?

Yes, the LT3971EDD-3.3#PBF can operate from a 5V input, but only if the minimum input voltage requirement of 4.3V is met. At 5V input, the device delivers full 1.2A output with typical efficiency >88% (per Figure G01), and maintains regulation down to ~3.8V input before dropout - verified in "TYPICAL PERFORMANCE CHARACTERISTICS" (Figure G19). Below 4.3V, EN must be grounded to ensure shutdown.

Does the LT3971EDD-3.3#PBF require an external catch diode?

No, the LT3971EDD-3.3#PBF does not require an external catch diode because it integrates a boost Schottky diode driver (BD pin) and relies on an external Schottky diode connected between BD and VOUT. The internal boost circuit drives this external diode to generate the higher-than-VIN voltage needed for NPN switch saturation - a key differentiator from synchronous buck controllers that integrate both FETs.

How does the power good (PG) flag behave during startup of the LT3971EDD-3.3#PBF?

During startup, the PG pin of the LT3971EDD-3.3#PBF remains low until VOUT reaches 91% of 3.3V (i.e., 3.003V), then transitions to high-impedance state, allowing an external pull-up to assert a logic-high signal. This behavior is confirmed in the "PIN FUNCTIONS" section and "ELECTRICAL CHARACTERISTICS" table (PG Threshold Offset = 5.5–12.5% of VOUT). PG is only valid when EN is high and VIN > 4.3V.

Is the LT3971EDD-3.3#PBF pin-compatible with other variants in the LT3971 family?

Yes, the LT3971EDD-3.3#PBF shares identical pinout and package (10-lead 3mm × 3mm DFN) with LT3971EDD#PBF, LT3971EDD-5#PBF, and all DFN-packaged LT3971 variants - including matching pin functions for BD, BOOST, SW, VIN, EN, VOUT/FB, SS, RT, PG, and SYNC. This allows direct substitution between fixed 3.3V, fixed 5V, and adjustable versions without PCB changes.