LTC1539 Datasheet | Linear Technology

Features s s s s s s s LTC1538-AUX/LTC1539 Dual High Efficiency, Low Noise, Synchronous Step-Down Switching Regulators DESCRIPTION The LTC ®1538-AUX/LTC1539 are dual, synchronous stepdown switching regulator controllers which drive external N-channel power MOSFETs in a phase-lockable fixed frequency architecture. The Adaptive Power TM output stage selectively drives two N-channel MOSFETs at frequencies up to 400k Hz while reducing switching losses to maintain high efficiencies at low output currents. An auxiliary 0.5A linear regulator using an external PNP pass device provides a low noise, low dropout voltage source. A secondary winding feedback control pin (SFB1) guarantees regulation regardless of load on the main output by forcing continuous operation. A 5V/20m A regulator, internal 1.19V reference and an unmitted parator remain active when both controllers are shut down. A power-on reset timer (POR) is included which generates a signal delayed by 65536/f CLK (typ 300ms) after the controller’s output is within 5% of the regulated first voltage. Internal resistive dividers provide pin selectable output voltages with remote sense capability on one of the two outputs. The operating current levels are user-programmable via external current sense resistors. Wide input supply range allows operation from 3.5V to 30V (36V maximum). , LTC and LT are registered trademarks of Linear Technology Corporation. Adaptive Power is a trademark of Linear Technology Corporation. s s s s s s s s s Maintains Constant Frequency at Low Output Currents Dual N-Channel MOSFET Synchronous Drive Programmable Fixed Frequency (PLL Lockable) Wide VIN Range: 3.5V to 36V Operation Ultrahigh Efficiency Very Low Dropout Operation: 99% Duty Cycle Low Dropout, 0.5A Linear Regulator for VPP Generation or Low Noise Audio Supply Built-In Power-On Reset Timer Programmable Soft Start Low-Battery Detector Remote Output Voltage Sense Foldback Current Limiting (Optional) Pin Selectable Output Voltage...