Analog Devices Inc. LT3973EMSE-3.3#TRPBF

Overview

LT3973EMSE-3.3#TRPBF from Analog Devices (formerly Linear Technology) is a fixed 3.3V, 42V-input, 750mA monolithic step-down regulator with integrated boost and catch diodes, 2.5µA quiescent current, and low-ripple Burst Mode® operation. It delivers automotive-grade power regulation in cold-crank conditions with 530mV minimum dropout voltage and a power good flag for system sequencing.

For engineers reviewing the LT3973EMSE-3.3#TRPBF datasheet, LT3973EMSE-3.3#TRPBF pinout, LT3973EMSE-3.3#TRPBF application, or LT3973EMSE-3.3#TRPBF equivalent, key selection criteria include its fixed 3.3V output, 10-lead MSOP package with exposed pad, –40°C to 125°C operating range, and compatibility with high-input-voltage industrial and automotive supply rails.

Technical Context

The LT3973EMSE-3.3#TRPBF implements constant-frequency current-mode control with programmable switching frequency (200kHz–2.2MHz) via RT pin resistor. Its internal bipolar NPN switch is driven by a charge-pump boosted gate voltage, enabling full saturation even at low VIN–VOUT differentials.

Burst Mode® operation reduces no-load input current to 1.8µA while maintaining <10mVP-P output ripple; an accurate 90% power-good threshold (PG) and programmable EN/UVLO (1.19V rising, 30mV hysteresis) support robust system-level power sequencing and fault management.

Key Specifications

Pinout & Package

LT3973EMSE-3.3#TRPBF uses a thermally enhanced 10-lead MSOP package (3mm × 3mm footprint) with exposed GND pad (Pin 11) requiring solder connection to PCB for thermal and electrical integrity.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar step-down regulator applications.

Compared with LT3973EMSE-3.3#TRPBF, LT8609SIS8E#TRPBF offers +1.25A output headroom and synchronous efficiency gains but lacks the same cold-crank dropout performance; TPS54332DDAR provides higher current at lower cost but demands external components and cannot replace LT3973EMSE-3.3#TRPBF in 42V or ultra-low-IQ designs.

Availability

LT3973EMSE-3.3#TRPBF is available at Aetrix Electronics and suitable for automotive body electronics, industrial IoT sensor nodes, portable medical diagnostics, and PLC I/O modules requiring stable component supply across extended temperature and high-reliability environments.

Supply support for LT3973EMSE-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 legacy of high-performance power management ICs with rigorous automotive and industrial qualification standards.

The LT3973 family was designed specifically for demanding 42V-input applications such as automotive infotainment, ADAS subsystems, and industrial power supplies where ultra-low quiescent current, integrated diodes, and cold-crank resilience are mandatory.

FAQ

What is the guaranteed output voltage accuracy of the LT3973EMSE-3.3#TRPBF over temperature?

The LT3973EMSE-3.3#TRPBF delivers 3.3V output with ±1.2% initial accuracy over the full –40°C to 125°C junction temperature range, as specified in the Electrical Characteristics table. This is achieved via laser-trimmed internal feedback resistors and process-matched bandgap references, ensuring stable 3.3V rail generation without external calibration.

Can the LT3973EMSE-3.3#TRPBF operate with input voltages below 4.2V?

Yes-the LT3973EMSE-3.3#TRPBF begins switching at ~3V input but regulates only down to 3.8V minimum for accurate 3.3V output. Below 4.2V, EN/UVLO functionality is disabled; for reliable cold-crank operation, tie EN/UVLO to GND to force enable and rely on the device's inherent dropout behavior with 530mV minimum VIN–VOUT differential.

How does the LT3973EMSE-3.3#TRPBF maintain low output ripple in Burst Mode® operation?

The LT3973EMSE-3.3#TRPBF achieves <10mVP-P ripple in Burst Mode® by minimizing energy per burst and tightly controlling burst frequency. During light loads, it shuts down all non-essential circuitry-including oscillator and error amplifier-reducing input current to 1.8µA while maintaining precise output voltage regulation through controlled pulse-width modulation of discrete energy packets.

Is an external boost capacitor required for the LT3973EMSE-3.3#TRPBF, and what value is recommended?

Yes-an external 0.47µF X7R ceramic capacitor is required between BOOST and SW pins to generate the gate-drive voltage for the internal bipolar NPN switch. This capacitor must be placed adjacent to the IC with minimal trace length to ensure low-ESL performance and reliable switch saturation across temperature and load conditions.

What thermal considerations apply to the LT3973EMSE-3.3#TRPBF in a 10-lead MSOP package?

The LT3973EMSE-3.3#TRPBF has θJA = 45°C/W in the MSOP package; successful thermal design requires soldering the exposed GND pad (Pin 11) to ≥2cm² of inner-layer copper pour with ≥4 thermal vias. At 750mA load and 12VIN→3.3VOUT, typical power dissipation is ~1.1W-requiring careful PCB layout to maintain junction temperature ≤125°C in 70°C ambient environments.