Analog Devices Inc. LT3973IDD-5#TRPBF

Overview

LT3973IDD-5#TRPBF from Analog Devices (formerly Linear Technology) is a 42V, 750mA fixed-output 5V monolithic buck switching regulator with integrated power switch, catch diode, and boost diode. It delivers ultralow 2.5µA quiescent current at 12V_IN, maintains <10mV_P-P output ripple in Burst Mode, and sustains regulation down to 530mV dropout - enabling reliable operation during automotive cold-crank events.

For engineers reviewing the LT3973IDD-5#TRPBF datasheet, LT3973IDD-5#TRPBF pinout, LT3973IDD-5#TRPBF application, or LT3973IDD-5#TRPBF equivalent, key selection criteria include its fixed 5V output, -40°C to 125°C industrial temperature grade, 10-lead 3mm × 3mm DFN package with exposed thermal pad, and integrated diode architecture eliminating external catch/boost diodes.

Technical Context

The LT3973IDD-5#TRPBF implements constant-frequency current-mode control with programmable 200kHz–2.2MHz switching via RT resistor, enabling optimization of efficiency vs. size trade-offs. Its bipolar NPN internal switch is driven by a charge-pump boosted gate voltage (via BOOST pin), ensuring full saturation even at high duty cycles.

It integrates dual current limiting: peak switch current limit (1.65A typ) and valley catch diode current limit (1.15A typ), providing robust short-circuit protection. The power-good (PG) flag asserts when V_OUT reaches 90% of 5V, and accurate programmable EN/UVLO (1.19V threshold, 45mV hysteresis) enables precise input voltage supervision.

Key Specifications

Pinout & Package

LT3973IDD-5#TRPBF uses a thermally enhanced 10-lead (3mm × 3mm) plastic DFN package with exposed GND pad (Pin 11) requiring PCB soldering for thermal and electrical integrity.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LT8609SIS8E#TRPBF and TPS54560QDGQRQ1, the LT3973IDD-5#TRPBF offers the smallest footprint and lowest I_Q among fixed-5V 42V-input regulators with fully integrated diodes - ideal for space- and battery-life-constrained industrial and portable designs where 750mA suffices.

Availability

LT3973IDD-5#TRPBF is available at Aetrix Electronics and suitable for automotive body electronics, industrial IoT sensor nodes, portable medical devices, and PLC I/O modules requiring stable component supply with guaranteed long-term availability.

Supply support for LT3973IDD-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 continues its legacy of high-performance power management ICs for demanding analog and mixed-signal applications.

The LT3973IDD-5#TRPBF belongs to the LT3973 family of ultralow-I_Q buck regulators designed specifically for battery-powered and automotive systems where extended standby life and cold-crank resilience are critical.

FAQ

What is the output voltage tolerance of the LT3973IDD-5#TRPBF over temperature?

The LT3973IDD-5#TRPBF delivers a fixed 5.0V output with ±1.2% tolerance across its full –40°C to 125°C operating junction temperature range, as specified in the Electrical Characteristics table. This accuracy is achieved via laser-trimmed internal feedback resistors and is independent of external component tolerances - ensuring consistent 5V regulation in automotive and industrial environments where ambient temperature varies widely. The LT3973IDD-5#TRPBF does not require external resistors to set V_OUT.

Can the LT3973IDD-5#TRPBF operate with input voltages below 4.2V?

The LT3973IDD-5#TRPBF can begin switching at input voltages as low as ~3V, but it only guarantees regulation to 5V when V_IN ≥ 4.2V. Below this, the internal reference degrades and output voltage drops proportionally. For reliable 5V operation, maintain V_IN ≥ 4.2V; during cold-crank, the device sustains regulation down to V_IN = V_OUT + 530mV (i.e., 5.53V). The LT3973IDD-5#TRPBF's EN/UVLO pin remains inactive below 4.2V unless externally biased.

How does the LT3973IDD-5#TRPBF achieve ultralow quiescent current?

The LT3973IDD-5#TRPBF achieves 2.5µA quiescent current through a combination of deep subthreshold biasing, clock-gated circuit blocks, and automatic transition into Burst Mode at light loads - where most internal circuitry shuts down between switching bursts. This architecture minimizes static current draw while preserving fast transient response and low output ripple. The LT3973IDD-5#TRPBF maintains this ultra-low I_Q across its full input voltage range (4.2V–42V) and temperature range (–40°C to 125°C).

Is an external catch diode required when using the LT3973IDD-5#TRPBF?

No - the LT3973IDD-5#TRPBF integrates both the catch Schottky diode and boost Schottky diode on-die, eliminating the need for external diodes. This integration reduces total solution size, component count, and forward-voltage losses. The internal catch diode is rated for 1.15A valley current and exhibits 550mV typical forward voltage at 200mA, as confirmed in the Electrical Characteristics table. The LT3973IDD-5#TRPBF's datasheet explicitly states "integrated boost and catch diodes" as a core feature.

What thermal considerations apply to the LT3973IDD-5#TRPBF's DFN package?

The LT3973IDD-5#TRPBF uses a 10-lead 3mm × 3mm DFN with exposed thermal pad (Pin 11), achieving θ_JA = 40°C/W when properly soldered to ≥2 cm² of 2-oz copper on the PCB. To ensure reliable operation at 750mA, the exposed pad must be fully soldered to a solid GND plane with ≥4 thermal vias (0.3mm diameter) connecting to inner/ground layers. Without adequate thermal relief, junction temperature rise may exceed limits - especially at high V_IN/V_OUT ratios. The LT3973IDD-5#TRPBF includes thermal shutdown with hiccup recovery to prevent damage during transient overloads.