LTC6908 - Dual Output Oscillator with Spread Spectrum Modulation

LT4363 - High Voltage Surge Stopper with Current Limit

LTC4417 - Prioritized PowerPath Controller

LT3975 - 42V, 2.5A, 2MHz Step-Down Switching Regulator with 2.7µA Quiescent Current

Features

Ultralow Quiescent Current:
2.7μA I_Q at 12V_IN to 3.3V_OUT
Low Ripple Burst Mode® Operation
Output Ripple < 15mV_P-P
Wide Input Range: Operation from 4.3V to 42V
2.5A Maximum Output Current
Excellent Start-Up and Dropout Performance
Adjustable Switching Frequency: 200kHz to 2MHz
Synchronizable Between 250kHz to 2MHz
Accurate Programmable Undervoltage Lockout
Low Shutdown Current: I_Q = 700nA
Power Good Flag
Soft-Start Capability
Thermal Shutdown Protection
Current Limit Foldback with Soft-Start Override
Saturating Switch Design: 75mΩ On Resistance
Small, Thermally Enhanced 16-Lead MSOP Package

Typical Application

Description

The LT®3975 is an adjustable frequency monolithic buck switching regulator that accepts a wide input voltage range up to 42V. Low quiescent current design consumes only 2.7μA 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. The LT3975 can supply up to 2.5A of load current and has current limit foldback to limit power dissipation during short circuit. A low dropout voltage of 500mV is maintained when the input voltage drops below the programmed output voltage, such as during automotive cold crank.

An internally compensated current mode topology is used for fast transient response and good loop stability. A high efficiency 75mΩ switch is included on the die along with a boost Schottky diode and the necessary oscillator, control, and logic circuitry. An accurate 1.02V threshold enable pin can be driven directly from a microcontroller or used as a programmable undervoltage lockout. A capacitor on the SS pin provides a controlled inrush current (soft-start). A power good flag signals when V_OUT reaches 91.6% of the programmed output voltage. The LT3975 is available in a small 16-lead MSOP package with exposed pad for low thermal resistance.

Packaging

For complete and up to date package information and drawings, please refer to our packaging page

MS-16

Order Info

Part numbers ending in PBF are lead free. Please contact LTC marketing for information on lead based finish parts.
Part numbers containing TR or TRM are shipped in tape and reel or 500 unit mini tape and reel, respectively
Please refer to our general ordering information or the product datasheet for more details

Package Variations and Pricing

Part Number	Package	Pins	Temp	Price (1-99)	Price (1k)^*	RoHS Data
LT3975EMSE#PBF	MSOP	16	E	$4.43	$3.10	View
LT3975EMSE#TRPBF	MSOP	16	E		$3.16	View
LT3975HMSE#PBF	MSOP	16	H	$5.23	$3.66	View
LT3975HMSE#TRPBF	MSOP	16	H		$3.72	View
LT3975IMSE#PBF	MSOP	16	I	$4.87	$3.41	View
LT3975IMSE#TRPBF	MSOP	16	I		$3.47	View
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^* The USA list pricing shown is for BUDGETARY USE ONLY, shown in United States dollars (FOB USA per unit for the stated volume), and is subject to change. International prices may differ due to local duties, taxes, fees and exchange rates. For volume-specific price or delivery quotes, please contact your local Linear Technology sales office or authorized distributor.

Demo Boards

Linear Technology offers many demo boards free of charge to qualified customers. Contact your local sales office or distributor to inquire about a demo board. Certain demo boards are also available for sale via credit card on this website. Demo boards are for evaluation purposes only. It remains the customer’s responsibility to verify proper and reliable operation in the actual end application.

Part Number	Description	Price	Documentation
DC1736A	LT3975 Demo Board I 42V, 2.5A, 2.7uA Micropower Buck Regulator	Contact Factory	Design File Manual Schematic ltspice
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Click here to view our complete list of demo boards

Applications

Automotive Battery Regulation
Portable Products
Industrial Supplies

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Simulate

LTspice IV is a powerful, fast and free simulation tool, schematic capture and waveform viewer with enhancements and models for improving the simulation of switching regulators. To download LTspice IV and other FREE simulation tools, please visit our Design Simulation page.

To launch a ready to run LTspice demonstration circuit for this part:

Step 1: If you have not installed LTspice on this computer, download and install LTspice IV
Step 2: Once LTspice is installed, click on the link(s) below to launch the simulation
- LT3975 Demo Circuit - 3.3V Step-Down Converter (4.3-42V to 3.3V @ 2.5A)
Step 3: If LTspice IV does not automatically open after clicking the link above, you can instead run the simulation by right clicking on the link and selecting "Save Target As". After saving the file to your computer, start LTspice and open the demonstration circuit by selecting 'Open' from the 'File' menu

To explore other ready to run LTspice demonstration circuits, please visit our Demo Circuits Collection.

Related models available in LTspice IV
LT3975

Technical Support

For immediate technical assistance, contact your local sales office or distributor or call 1-800-4-LINEAR (US customers only) or 408-432-1900.
For less urgent requests, please complete our Technical Support Request Form. Please allow 2-3 business days for reply.