The BU90009GWZ from ROHM Semiconductor is an Isolated Buck DC-DC Converter that converts a DC input voltage of 2.3 - 5.5 V to a DC output voltage of 1.30 V. It includes a switching control logic circuit within an integrated gate driver, error compensation block, Pulse Width Modulation(PWM)/Pulse Frequency Modulation (PFM) control circuit, power MOSFETs, and protection circuits. This DC-DC converter integrates a mode control pin that allows the user to select forced PWM mode or PFM mode, thereby offering efficient power management. It is equipped with an auto-change mode function that provides power-saving operation under light load current conditions. This RoHS-compliant converter is available in a surface-mount package that measures 1.30 x 0.90 x 0.40 mm and is ideal for smartphones, cell phones, micro DC/DC modules, USB accessories, and portable applications.