LT3971A/LT3971A-5 38V, 1.3A, 2MHz Step-Down Regulator with 2.2µA Quiescent Current FEATURESDESCRIPTION n Ultralow Quiescent Current: The LT®3971A is an adjustable frequency monolithic buck 2.8μA IQ Regulating 12VIN to 3.3VOUT switching regulator that accepts a wide input voltage range n Fixed Output Voltages: 5V up to 38V. Low quiescent current design consumes only 2.2μA IQ Regulating 12VIN to 5VOUT 2.8μA of supply current while regulating with no load. Low n Low Ripple Burst Mode ® Operation: ripple Burst Mode operation maintains high efficiency at Output Ripple < 15mVP-P low output currents while keeping the output ripple below n Wide Input Voltage Range: 4.3V to 38V 15mV in a typical application. An internally compensated n 1.3A Maximum Output Current current mode topology is used for fast transient response n Adjustable Switching Frequency: 200kHz to 2MHz and good loop stability. A high efficiency 0.33Ω switch n Synchronizable Between 250kHz to 2MHz is included on the die along with a boost Schottky diode n Fast Transient Response and the necessary oscillator, control and logic circuitry. n Accurate 1V Enable Pin Threshold An accurate 1V threshold enable pin can be used to shut n Low Shutdown Current: IQ = 700nA down the LT3971A, reducing the input supply current to n Power Good Flag 700nA. A capacitor on the SS pin provides a controlled n Soft-Start Capability inrush current (soft-start). A power good flag signals when n Internal Compensation VOUT reaches 91% of the programmed output voltage. The n Output Voltage: 1.19V to 30V LT3971A is available in a small 10-lead MSOP package n Small Thermally Enhanced 10-Lead MSOP Package with an exposed pad for low thermal resistance. The LT3971A and LT3971A-5 have a more accurate ref- APPLICATIONS erence voltage compared to the LT3971 and LT3971-5. The LT3971A-5 also has specified VOUT pin current and n USB VBUS Regulation ABSMAX current. These characteristics are important for n Automotive Battery Regulation USB applications. n Power for Portable Products L, LT, LTC, LTM, Linear Technology, Burst Mode and the Linear logo are registered trademarks n Industrial Supplies of Linear Technology Corporation. All other trademarks are the property of their respective owners. TYPICAL APPLICATIONNo Load Supply Current5.15V Step-Down Converter for USB Applications 3.0 OUTPUT IN REGULATION VIN 6.3V TO 38V V 2.5 IN LT3971A-5 OFF ON EN BOOST 0.47μF 10μH PG SW 2.0 SS 4.7μF LT3971A-5 RT INPUT CURRENT (μA) BD 1.5 20k, 1% VOUT VOUT 5.15V 118k SYNC GND 1.3A 715k 47μF 1.0 1% f = 400kHz 5 10 15 20 25 30 35 3971 TA01a INPUT VOLTAGE (V) 3971A TA01b 3971af 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
