LT3991

PRODUCTION

55V, 1.2A Step-Down Regulator with 2.8μA Quiescent Current

Part Models: 16
1ku List Price: Starting From $3.54

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Overview

Ultralow Quiescent Current: 2.8μA I_Q Regulating 12V_IN to 3.3V_OUT
Fixed Output Voltages: 3.3V, 5V 2.1μA I_Q Regulating 12V_IN
Low Ripple Burst Mode^® Operation: Output Ripple < 15mV_P-P
Wide Input Voltage Range: 4.3V to 55V
1.2A Maximum Output Current
Adjustable Switching Frequency: 200kHz to 2MHz
Synchronizable Between 250kHz to 2MHz
Fast Transient Response
Accurate 1V Enable Pin Threshold
Low Shutdown Current: I_Q = 700nA
Power Good Flag
Soft-Start CapabilityV
Internal Compensation
Saturating Switch Design: 0.44Ω On-Resistance
Output Voltage: 1.19V to 30V
Small Thermally Enhanced 10-Pin MSOP Package and (3mm × 3mm) DFN Packages

The LT3991 is an adjustable frequency monolithic buck switching regulator that accepts a wide input voltage range up to 55V. Low quiescent current design consumes only 2.8μA of supply current while regulating with no load. Low ripple Burst Mode operation maintains high efficiency at low output currents while keeping the output ripple below 15mV in a typical application. An internally compensated current mode topology is used for fast transient response and good loop stability. A high efficiency 0.44Ω switch is included on the die along with a boost Schottky diode and the necessary oscillator, control and logic circuitry. An accurate 1V threshold enable pin can be used to shut down the LT3991, reducing the input supply current to 700nA. A capacitor on the SS pin provides a controlled inrush current (soft-start). A power good flag signals when V_OUT reaches 91% of the programmed output voltage. The LT3991 is available in small 10-pin MSOP and 3mm × 3mm DFN packages with exposed pads for low thermal resistance.

Applications

Automotive Battery Regulation
Power for Portable Products
Industrial Supplies

Part Models: 16
1ku List Price: Starting From $3.54

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
LT3991EDD#PBF	10-Lead DFN (3mm x 3mm w/ EP)	Material Declaration Reliablity Data Package Resources	Ultra Librarian SamacSys
LT3991EDD#TRPBF	10-Lead DFN (3mm x 3mm w/ EP)	Material Declaration Reliablity Data Package Resources	Ultra Librarian SamacSys
LT3991EMSE#PBF	10-Lead MSOP w/ EP	Material Declaration Reliablity Data Package Resources	Ultra Librarian SamacSys
LT3991EMSE#TRPBF	10-Lead MSOP w/ EP	Material Declaration Reliablity Data Package Resources	Ultra Librarian SamacSys
LT3991EMSE-3.3#PBF	10-Lead MSOP w/ EP	Material Declaration Reliablity Data Package Resources	Ultra Librarian SamacSys
LT3991EMSE-3.3#TRPBF	10-Lead MSOP w/ EP	Material Declaration Reliablity Data Package Resources	Ultra Librarian SamacSys
LT3991EMSE-5#PBF	10-Lead MSOP w/ EP	Material Declaration Reliablity Data Package Resources	Ultra Librarian SamacSys
LT3991EMSE-5#TRPBF	10-Lead MSOP w/ EP	Material Declaration Reliablity Data Package Resources	Ultra Librarian SamacSys
LT3991IDD#PBF	10-Lead DFN (3mm x 3mm w/ EP)	Material Declaration Reliablity Data Package Resources	Ultra Librarian SamacSys
LT3991IDD#TRPBF	10-Lead DFN (3mm x 3mm w/ EP)	Material Declaration Reliablity Data Package Resources	Ultra Librarian SamacSys
LT3991IMSE#PBF	10-Lead MSOP w/ EP	Material Declaration Reliablity Data Package Resources	Ultra Librarian SamacSys
LT3991IMSE#TRPBF	10-Lead MSOP w/ EP	Material Declaration Reliablity Data Package Resources	Ultra Librarian SamacSys
LT3991IMSE-3.3#PBF	10-Lead MSOP w/ EP	Material Declaration Reliablity Data Package Resources	Ultra Librarian SamacSys
LT3991IMSE-3.3#TRPBF	10-Lead MSOP w/ EP	Material Declaration Reliablity Data Package Resources	Ultra Librarian SamacSys
LT3991IMSE-5#PBF	10-Lead MSOP w/ EP	Material Declaration Reliablity Data Package Resources	Ultra Librarian SamacSys
LT3991IMSE-5#TRPBF	10-Lead MSOP w/ EP	Material Declaration Reliablity Data Package Resources	Ultra Librarian SamacSys

Part Models	Product Lifecycle	PCN

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
LT3991EMSE#PBF	PRODUCTION
LT3991EMSE#TRPBF	PRODUCTION
LT3991EMSE-3.3#PBF	PRODUCTION
LT3991EMSE-3.3#TRPBF	PRODUCTION
LT3991EMSE-5#PBF	PRODUCTION
LT3991EMSE-5#TRPBF	PRODUCTION
LT3991IMSE#PBF	PRODUCTION
LT3991IMSE#TRPBF	PRODUCTION
LT3991IMSE-3.3#PBF	PRODUCTION
LT3991IMSE-3.3#TRPBF	PRODUCTION
LT3991IMSE-5#PBF	PRODUCTION
LT3991IMSE-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
LT3991EMSE#PBF	PRODUCTION
LT3991EMSE#TRPBF	PRODUCTION
LT3991EMSE-3.3#PBF	PRODUCTION
LT3991EMSE-3.3#TRPBF	PRODUCTION
LT3991EMSE-5#PBF	PRODUCTION
LT3991EMSE-5#TRPBF	PRODUCTION
LT3991IMSE#PBF	PRODUCTION
LT3991IMSE#TRPBF	PRODUCTION
LT3991IMSE-3.3#PBF	PRODUCTION
LT3991IMSE-3.3#TRPBF	PRODUCTION
LT3991IMSE-5#PBF	PRODUCTION
LT3991IMSE-5#TRPBF	PRODUCTION

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

Software Resources

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Hardware Ecosystem

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Tools & Simulations

LTspice 1

LT3991 Demo Circuit - 55V 1.2A 2MHz Step-Down Regulator with 2.8µA Iq (12V to 3.3V @ 1.2A)

Models for the following parts are available in LTspice:

LT3991

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

LT3991EMSE Demo Board | 55V, 1.2A, Step-Down Regulator with 2.8µA Quiescent Current

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Product Details

Demonstration circuit 1526 is a monolithic step-down DC/DC switching regulator featuring the LT3991. The switching frequency is adjustable up to 2MHz. The demo circuit is designed for 3.3V, 1.2A output from a 4.5V to 55V input. The wide input range of the LT3991 allows a variety of input sources including automotive batteries and 24V industrial supplies. Low ripple Burst Mode increases the efficiency at the light load while keeping the output ripple below 15mV. The part is in shutdown when the EN pin is low and active when the pin is high. The threshold of the EN pin is accurate at 1.01V with 30mV of hysteresis. When V_IN is above 6V, adding a resistor divider from V_IN to EN can program the LT3991 to regulate the output only when V_IN is above a desired voltage. The circuit consumes only 2.8μA of quiescent current. The boost diode, control and logic circuit are integrated to reduce the components count and solution size. The current mode control scheme creates fast transient response and good loop stability.

Resources

DC1526A - Schematic
3/12/2010

DC1526A - Demo Manual
3/12/2010

DC1526A - Design Files
3/12/2010

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