The LT1938 is an adjustable frequency (300kHz to 2.8MHz) monolithic buck switching regulator that accepts input voltages up to 25V. A high efficiency 0.18Ω switch is included on the die along with a boost Schottky diode and the necessary oscillator, control and logic circuitry. Current mode topology is used for fast transient response and good loop stability. The LT1938's high operating frequency allows the use of small, low cost inductors and ceramic capacitors resulting in low output ripple while keeping total solution size to a minimum. The low current shutdown mode reduces input supply current to less than 1µA while a resistor and capacitor on the RUN/SS pin provide a controlled output voltage ramp (soft-start). A power good flag signals when VOUTreaches 90% of the programmed output voltage. The LT1938 is available in a 3mm × 3mm DFN package with Exposed Pad for low thermal resistance.ApplicationsAutomotive Battery RegulationPower for Portable ProductsDistributed Supply RegulationIndustrial SuppliesWall Transformer Regulation