The ISL91128 is a high-current, buck-boost switching regulator for systems using new battery chemistries. It uses the Renesas proprietary buck-boost algorithm to maintain voltage regulation while providing excellent efficiency and very low output voltage ripple when the input voltage is close to the output voltage. The device also includes a selectable Bypass mode for low power consumption in applications that have a Sleep or Low Power mode. The ISL91128 is capable of delivering at least 2.2A continuous output current (VOUT = 3.3V) across a battery voltage range of 2.5V to 4.35V. This maximizes the energy utilization of advanced, single-cell Li-ion battery chemistries that have significant capacity left at voltages below the system voltage. Its fully synchronous low ON-resistance 4-switch architecture and a low quiescent current of only 30µA optimize efficiency under all load conditions. The ISL91128 supports a broader set of programmable features that can be accessed using an I2C bus interface. With a programmable output voltage range of 1.9V to 5.0V, the ISL91128 is ideal for applications requiring dynamically changing supply voltages. A programmable slew rate can be selected to provide smooth transitions between output voltage settings. The ISL91128 is available in a 20-bump, 0.4mm pitch WLCSP (2.15mm x 1.74mm) with a 2.5MHz switching frequency, which further reduces the size of external components.