LT3973

PRODUCTION

42V, 750mA Step-Down Regulator with 2.5μA Quiescent Current and Integrated Diodes

Part Models: 36
1ku List Price: Starting From $3.31

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Overview

Ultralow Quiescent Current
2.5μA I_Q at 12V_IN to 3.3V_OUT
Low Ripple Burst Mode^® Operation
Output Ripple < 10mV_P-P
Wide Input Voltage Range: 4.2V to 42V Operating
Adjustable Switching Frequency: 200kHz to 2.2MHz
Integrated Boost and Catch Diodes
750mA Output Current
Excellent Start-Up and Dropout Performance
Fixed Output Voltages: 3.3V, 5V
- 1.9μA I_Q at 12V_IN
Accurate Programmable Undervoltage Lockout
Low Shutdown Current: I_Q = 0.75μA
Internal Catch Diode Current Limit
Power Good Flag
Thermal Shutdown
Small, Thermally Enhanced 10-Lead MSOP and (3mm × 3mm) DFN Packages

The LT3973 is an adjustable frequency monolithic buck switching regulator that accepts a wide input voltage range up to 42V, and consumes only 2.5μA of quiescent current. A high efficiency switch is included on the die along with the catch diode, boost diode, and the necessary oscillator, control and logic circuitry. Low ripple Burst Mode operation maintains high efficiency at low output currents while keeping the output ripple below 10mV in a typical application. A minimum dropout voltage of 530mV is maintained when the input voltage drops below the programmed output voltage, such as during automotive cold crank. Current mode topology is used for fast transient response and good loop stability. A catch diode current limit provides protection against shorted outputs and overvoltage conditions, with thermal shutdown providing additional fault protection. An accurate programmable undervoltage lockout feature is available, producing a low shutdown current of 0.75μA. A power good flag signals when V_OUT reaches 90% of the programmed output voltage. The LT3973 is available in small, thermally enhanced 10-lead MSOP and 3mm × 3mm DFN packages.

Applications

Automotive Battery Regulation
Power for Portable Products
Industrial Supplies
Gate Drive Bias

Part Models: 36
1ku List Price: Starting From $3.31

Documentation

ADI has always placed the highest emphasis on delivering products that meet the maximum levels of quality and reliability. We achieve this by incorporating quality and reliability checks in every scope of product and process design, and in the manufacturing process as well. "Zero defects" for shipped products is always our goal. View our quality and reliability program and certifications for more information.

Part Model	Pin/Package Drawing	Documentation	CAD Symbols, Footprints, and 3D Models
LT3973EDD#PBF	10-Lead DFN (3mm x 3mm w/ EP)	Material Declaration Reliablity Data Package Resources	Ultra Librarian SamacSys
LT3973EDD#TRPBF	10-Lead DFN (3mm x 3mm w/ EP)	Material Declaration Reliablity Data Package Resources	Ultra Librarian SamacSys
LT3973EDD-3.3#PBF	10-Lead DFN (3mm x 3mm w/ EP)	Material Declaration Reliablity Data Package Resources	Ultra Librarian SamacSys
LT3973EDD-3.3#TRPBF	10-Lead DFN (3mm x 3mm w/ EP)	Material Declaration Reliablity Data Package Resources	Ultra Librarian SamacSys
LT3973EDD-5#PBF	10-Lead DFN (3mm x 3mm w/ EP)	Material Declaration Reliablity Data Package Resources	Ultra Librarian SamacSys
LT3973EDD-5#TRPBF	10-Lead DFN (3mm x 3mm w/ EP)	Material Declaration Reliablity Data Package Resources	Ultra Librarian SamacSys
LT3973EMSE#PBF	10-Lead MSOP w/ EP	Material Declaration Reliablity Data Package Resources	Ultra Librarian SamacSys
LT3973EMSE#TRPBF	10-Lead MSOP w/ EP	Material Declaration Reliablity Data Package Resources	Ultra Librarian SamacSys
LT3973EMSE-3.3#PBF	10-Lead MSOP w/ EP	Material Declaration Reliablity Data Package Resources	Ultra Librarian SamacSys
LT3973EMSE-3.3#TRPBF	10-Lead MSOP w/ EP	Material Declaration Reliablity Data Package Resources	Ultra Librarian SamacSys
LT3973EMSE-5#PBF	10-Lead MSOP w/ EP	Material Declaration Reliablity Data Package Resources	Ultra Librarian SamacSys
LT3973EMSE-5#TRPBF	10-Lead MSOP w/ EP	Material Declaration Reliablity Data Package Resources	Ultra Librarian SamacSys
LT3973HDD#PBF	10-Lead DFN (3mm x 3mm w/ EP)	Material Declaration Reliablity Data Package Resources	Ultra Librarian SamacSys
LT3973HDD#TRPBF	10-Lead DFN (3mm x 3mm w/ EP)	Material Declaration Reliablity Data Package Resources	Ultra Librarian SamacSys
LT3973HDD-3.3#PBF	10-Lead DFN (3mm x 3mm w/ EP)	Material Declaration Reliablity Data Package Resources	Ultra Librarian SamacSys
LT3973HDD-3.3#TRPBF	10-Lead DFN (3mm x 3mm w/ EP)	Material Declaration Reliablity Data Package Resources	Ultra Librarian SamacSys
LT3973HDD-5#PBF	10-Lead DFN (3mm x 3mm w/ EP)	Material Declaration Reliablity Data Package Resources	Ultra Librarian SamacSys
LT3973HDD-5#TRPBF	10-Lead DFN (3mm x 3mm w/ EP)	Material Declaration Reliablity Data Package Resources	Ultra Librarian SamacSys
LT3973HMSE#PBF	10-Lead MSOP w/ EP	Material Declaration Reliablity Data Package Resources	Ultra Librarian SamacSys
LT3973HMSE#TRPBF	10-Lead MSOP w/ EP	Material Declaration Reliablity Data Package Resources	Ultra Librarian SamacSys
LT3973HMSE-3.3#PBF	10-Lead MSOP w/ EP	Material Declaration Reliablity Data Package Resources	Ultra Librarian SamacSys
LT3973HMSE-3.3#TRPBF	10-Lead MSOP w/ EP	Material Declaration Reliablity Data Package Resources	Ultra Librarian SamacSys
LT3973HMSE-5#PBF	10-Lead MSOP w/ EP	Material Declaration Reliablity Data Package Resources	Ultra Librarian SamacSys
LT3973HMSE-5#TRPBF	10-Lead MSOP w/ EP	Material Declaration Reliablity Data Package Resources	Ultra Librarian SamacSys
LT3973IDD#PBF	10-Lead DFN (3mm x 3mm w/ EP)	Material Declaration Reliablity Data Package Resources	Ultra Librarian SamacSys
LT3973IDD#TRPBF	10-Lead DFN (3mm x 3mm w/ EP)	Material Declaration Reliablity Data Package Resources	Ultra Librarian SamacSys
LT3973IDD-3.3#PBF	10-Lead DFN (3mm x 3mm w/ EP)	Material Declaration Reliablity Data Package Resources	Ultra Librarian SamacSys
LT3973IDD-3.3#TRPBF	10-Lead DFN (3mm x 3mm w/ EP)	Material Declaration Reliablity Data Package Resources	Ultra Librarian SamacSys
LT3973IDD-5#PBF	10-Lead DFN (3mm x 3mm w/ EP)	Material Declaration Reliablity Data Package Resources	Ultra Librarian SamacSys
LT3973IDD-5#TRPBF	10-Lead DFN (3mm x 3mm w/ EP)	Material Declaration Reliablity Data Package Resources	Ultra Librarian SamacSys
LT3973IMSE#PBF	10-Lead MSOP w/ EP	Material Declaration Reliablity Data Package Resources	Ultra Librarian SamacSys
LT3973IMSE#TRPBF	10-Lead MSOP w/ EP	Material Declaration Reliablity Data Package Resources	Ultra Librarian SamacSys
LT3973IMSE-3.3#PBF	10-Lead MSOP w/ EP	Material Declaration Reliablity Data Package Resources	Ultra Librarian SamacSys
LT3973IMSE-3.3#TRPBF	10-Lead MSOP w/ EP	Material Declaration Reliablity Data Package Resources	Ultra Librarian SamacSys
LT3973IMSE-5#PBF	10-Lead MSOP w/ EP	Material Declaration Reliablity Data Package Resources	Ultra Librarian SamacSys
LT3973IMSE-5#TRPBF	10-Lead MSOP w/ EP	Material Declaration Reliablity Data Package Resources	Ultra Librarian SamacSys

Part Models	Product Lifecycle	PCN

Apr 17, 2025 - 25_0043 Change of Gold to Copper Wire and BOM (Automotive)
		PCN25_0043_Form Material_Report Delta Qualification Matrix Qualification Results Summary
LT3973EDD#PBF	PRODUCTION
LT3973EDD#TRPBF	PRODUCTION
LT3973EDD-3.3#PBF	PRODUCTION
LT3973EDD-3.3#TRPBF	PRODUCTION
LT3973EDD-5#PBF	PRODUCTION
LT3973EDD-5#TRPBF	PRODUCTION
LT3973HDD#PBF	PRODUCTION
LT3973HDD#TRPBF	PRODUCTION
LT3973HDD-3.3#PBF	PRODUCTION
LT3973HDD-3.3#TRPBF	PRODUCTION
LT3973HDD-5#PBF	PRODUCTION
LT3973HDD-5#TRPBF	PRODUCTION
LT3973IDD-3.3#PBF	PRODUCTION
LT3973IDD-3.3#TRPBF	PRODUCTION
LT3973IDD-5#PBF	PRODUCTION
LT3973IDD-5#TRPBF	PRODUCTION
Apr 17, 2025 - 25_0119 Bond Wire Change from Gold to Copper (Automotive)
		PCN25_0119_Form Material_Report Delta Qualification Matrix Qualification Results Summary
LT3973EMSE#PBF	PRODUCTION
LT3973EMSE#TRPBF	PRODUCTION
LT3973EMSE-3.3#PBF	PRODUCTION
LT3973EMSE-3.3#TRPBF	PRODUCTION
LT3973EMSE-5#PBF	PRODUCTION
LT3973EMSE-5#TRPBF	PRODUCTION
LT3973HMSE#PBF	PRODUCTION
LT3973HMSE#TRPBF	PRODUCTION
LT3973HMSE-3.3#PBF	PRODUCTION
LT3973HMSE-3.3#TRPBF	PRODUCTION
LT3973HMSE-5#PBF	PRODUCTION
LT3973HMSE-5#TRPBF	PRODUCTION
LT3973IMSE-3.3#PBF	PRODUCTION
LT3973IMSE-3.3#TRPBF	PRODUCTION
LT3973IMSE-5#PBF	PRODUCTION
LT3973IMSE-5#TRPBF	PRODUCTION
Jun 5, 2024 - 24_0003 Epoxy Change from Henkel 8290 to 8290A for MSOP Package (2)
		PCN24_0003_Form Material_Report Qualification Results Summary Delta Qualification Matrix
LT3973EMSE#PBF	PRODUCTION
LT3973EMSE#TRPBF	PRODUCTION
LT3973EMSE-3.3#PBF	PRODUCTION
LT3973EMSE-3.3#TRPBF	PRODUCTION
LT3973EMSE-5#PBF	PRODUCTION
LT3973EMSE-5#TRPBF	PRODUCTION
LT3973HMSE#PBF	PRODUCTION
LT3973HMSE#TRPBF	PRODUCTION
LT3973HMSE-3.3#PBF	PRODUCTION
LT3973HMSE-3.3#TRPBF	PRODUCTION
LT3973HMSE-5#PBF	PRODUCTION
LT3973HMSE-5#TRPBF	PRODUCTION
LT3973IMSE-3.3#PBF	PRODUCTION
LT3973IMSE-3.3#TRPBF	PRODUCTION
LT3973IMSE-5#PBF	PRODUCTION
LT3973IMSE-5#TRPBF	PRODUCTION
Feb 4, 2020 - 20_0130 Laser Top Mark Conversion for 10-Lead MSOP Packages Assembled in ADPG and UTAC
		PCN20_0130_Form Material_Report
LT3973EMSE#PBF	PRODUCTION
LT3973EMSE#TRPBF	PRODUCTION
LT3973EMSE-3.3#PBF	PRODUCTION
LT3973EMSE-3.3#TRPBF	PRODUCTION
LT3973EMSE-5#PBF	PRODUCTION
LT3973EMSE-5#TRPBF	PRODUCTION
LT3973HMSE#PBF	PRODUCTION
LT3973HMSE#TRPBF	PRODUCTION
LT3973HMSE-3.3#PBF	PRODUCTION
LT3973HMSE-3.3#TRPBF	PRODUCTION
LT3973HMSE-5#PBF	PRODUCTION
LT3973HMSE-5#TRPBF	PRODUCTION
LT3973IMSE#PBF	PRODUCTION
LT3973IMSE#TRPBF	PRODUCTION
LT3973IMSE-3.3#PBF	PRODUCTION
LT3973IMSE-3.3#TRPBF	PRODUCTION
LT3973IMSE-5#PBF	PRODUCTION
LT3973IMSE-5#TRPBF	PRODUCTION
Oct 11, 2022 - 22_0244 Epoxy Change from Henkel 8290 to 8290A for MSOP Package
		PCN22_0244_Form Material_Report Qualification Results Summary Delta Qualification Matrix
LT3973IMSE#PBF	PRODUCTION
LT3973IMSE#TRPBF	PRODUCTION
Jul 12, 2022 - 22_0157 UTAC Thai Limited (UTL) as Alternate Assembly Site for MSOP Packages [With Modification in BOM]
		PCN22_0157_Form Material_Report Qualification Results Summary Delta Qualification Matrix Detailed Parts List
LT3973IMSE#PBF	PRODUCTION
LT3973IMSE#TRPBF	PRODUCTION
Jun 21, 2022 - 22_0050 UTAC Thai Limited (UTL) as Alternate Assembly Site for MSOP Packages / Devices
		PCN22_0050_Form Material_Report Qualification Results Summary Delta Qualification Matrix
LT3973IMSE#PBF	PRODUCTION
LT3973IMSE#TRPBF	PRODUCTION

This is the most up-to-date revision of the Data Sheet.

Software Resources

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Hardware Ecosystem

Parts	Product Life Cycle	Description
Circuit Monitors 1
LTC2960	RECOMMENDED FOR NEW DESIGNS	36V Nano-Current Two-Input Voltage Monitor
Protection Switches & Controllers 2
LTC4365	RECOMMENDED FOR NEW DESIGNS	Overvoltage, Undervoltage and Reverse Supply Protection Controller
LTC4359	RECOMMENDED FOR NEW DESIGNS	Ideal Diode Controller with Reverse Input Protection

Tools & Simulations

LTspice 1

LT3973 Demo Circuit - µPower High Voltage Buck Regulator with Integrated Diodes (5.6-42V to 5V @ 750mA)

Models for the following parts are available in LTspice:

LT3973

LTspice® is a powerful, fast and free simulation software, schematic capture and waveform viewer with enhancements and models for improving the simulation of analog circuits.

Evaluation Kits

LT3973EMSE Demo Board | 42V, 750mA Step-Down Regulator with 2.5µA Quiescent Current

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Product Details

Demonstration circuit 1730A features the LT3973, a monolithic step-down switching regulator which consumes only 2.5μA quiescent current. The demo circuit is designed for a 5V, 750mA output from a 5.6V to 42V input. The wide input range of the LT3973 allows a variety of input sources including automotive batteries and 24V industrial supplies. In order to reduce the number of components and solution size, the catch diode and boost diode are integrated. The switching frequency is adjustable up to 2.2MHz. At light loads, the regulator operates in Burst Mode^® to maintain high efficiency and low output ripple.

Resources

DC1730A - Demo Manual
11/16/2011

DC1730A - Design Files
12/14/2011

DC1730A - Schematic
12/14/2011

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