LT3975 42V, 2.5A, 2MHz Step-Down Switching Regulator with 2.7µA Quiescent Current FEATURESDESCRIPTION n Ultralow Quiescent Current: The LT®3975 is an adjustable frequency monolithic buck 2.7µAIQ at 12VIN to 3.3VOUT switching regulator that accepts a wide input voltage range n Low Ripple Burst Mode® Operation up to 42V. Low quiescent current design consumes only Output Ripple < 15mVP-P 2.7µA of supply current while regulating with no load. Low n Wide Input Range: Operation from 4.3V to 42V ripple Burst Mode operation maintains high efficiency at n 2.5A Maximum Output Current low output currents while keeping the output ripple below n Excellent Start-Up and Dropout Performance 15mV in a typical application. The LT3975 can supply up n Adjustable Switching Frequency: 200kHz to 2MHz to 2.5A of load current and has current limit foldback to n Synchronizable Between 250kHz to 2MHz limit power dissipation during short circuit. A low dropout n Accurate Programmable Undervoltage Lockout voltage of 500mV is maintained when the input voltage n Low Shutdown Current: IQ = 700nA drops below the programmed output voltage, such as n Power Good Flag during automotive cold crank. n Soft-Start Capability An internally compensated current mode topology is used n Thermal Shutdown Protection for fast transient response and good loop stability. A high n Current Limit Foldback with Soft-Start Override efficiency 75mΩ switch is included on the die along with a n Saturating Switch Design: 75mΩ On Resistance boost Schottky diode and the necessary oscillator, control, n Small, Thermally Enhanced 16-Lead MSOP Package and logic circuitry. An accurate 1.02V threshold enable pin APPLICATIONS can be driven directly from a microcontroller or used as a programmable undervoltage lockout. A capacitor on the n Automotive Battery Regulation SS pin provides a controlled inrush current (soft-start). n Portable Products A power good flag signals when VOUT reaches 91.6% of n Industrial Supplies the programmed output voltage. The LT3975 is available L, LT, LTC, LTM, Burst Mode, Linear Technology and the Linear logo are registered trademarks in a small 16-lead MSOP package with exposed pad for of Linear Technology Corporation. All other trademarks are the property of their respective owners. low thermal resistance. TYPICAL APPLICATIONNo-Load Supply Current3.3V Step-Down Converter 4.5 IN REGULATION VIN 4.3V TO 42V 4.0 VIN 3.5 OFF ON EN BOOST 0.47µF 3.3µH PG SW 3.0 10µF PDS560 LT3975 2.5 SS OUT INPUT CURRENT (µA) 2.0 1M VOUT RT FB 3.3V 10pF 1.5 10nF 2.5A SYNC GND 47µF 78.7k 576k 1210 1.0 0 5 10 15 20 25 30 35 40 45 3975 TA01a f = 600kHz INPUT VOLTAGE (V) 3975 TA01b 3975f 1 Document Outline FEATURES DESCRIPTION APPLICATIONS TYPICAL APPLICATION ABSOLUTE MAXIMUM RATINGS PIN CONFIGURATION ORDER INFORMATION ELECTRICAL CHARACTERISTICS TYPICAL PERFORMANCE CHARACTERISTICS PIN FUNCTIONS BLOCK DIAGRAM OPERATION APPLICATIONS INFORMATION TYPICAL APPLICATIONS PACKAGE DESCRIPTION TYPICAL APPLICATION RELATED PARTS
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