LT3976

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40V, 5A, 2MHz Step-Down Switching Regulator with 3.3μA Quiescent Current

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Overview

  • Ultralow Quiescent Current:
    • 3.3μA IQ at 12VIN to 3.3VOUT
  • Low Ripple Burst Mode® Operation
    • Output Ripple < 15mVP-P
  • Wide Input Range: Operation from 4.3V to 40V
  • 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: IQ = 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 and 24-Lead 3mm × 5mm QFN Packages

The LT3976 is an adjustable frequency monolithic buck switching regulator that accepts a wide input voltage range up to 40V. Low quiescent current design consumes only 3.3μA 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 LT3976 can supply up to 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. 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 VOUT reaches 91.6% of the programmed output voltage. The LT3976 is available in small 16-lead MSOP and 24-lead 3mm × 5mm QFN packages with exposed pad for low thermal resistance.

Applications

  • Automotive Battery Regulation
  • Portable Products
  • Industrial Supplies
LT3976
40V, 5A, 2MHz Step-Down Switching Regulator with 3.3μA Quiescent Current
3.3V Step-Down Converter No-Load Supply Current Product Package 1 Product Package 2
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Documentation

Data Sheet 1

Reliability Data 1

User Guide 1

Data Sheet

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Software Resources

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Hardware Ecosystem

Parts Product Life Cycle Description
Oscillators 1
LTC6908
Resistor Set SOT-23 Oscillator with Spread Spectrum Modulation
Protection Switches & Controllers 1
LT4363
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Tools & Simulations

LTspice 2

Models for the following parts are available in LTspice:

  • LT3976
LTspice

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

eval board
schematic 1
DC1848A

LT3976 Demo Board I Buck with 3.3µA Iq, 4.3V ≤ VIN ≤ 40V, VOUT = 3.3V @ 5A

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Product Details

Demonstration circuit 1848A is a monolithic step-down DC/DC switching regulator featuring the LT3976. The LT3976 is a compact, high efficiency, high speed monolithic stepdown switching regulator that consumes only 3.3μA of quiescent current. The demo circuit is designed for 3.3V, 5A output from a 4.3V to 40V input. The switching frequency can be programmed either via oscillator resistor or external clock up to 2MHz. To synchronize to an external clock, move JP2 to SYNC and apply the external clock to the SYNC turret.
DC1848A
LT3976 Demo Board I Buck with 3.3µA Iq, 4.3V ≤ VIN ≤ 40V, VOUT = 3.3V @ 5A
DC1848A - Schematic

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