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 I2 C 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 (2.15mmx1.74mm) with a 2.5MHz switching frequency, which further reduces the size of external components.


  • Accepts input voltages above or below regulated output voltage
  • Automatic and seamless transitions between Buck and Boost modes
  • I2C interface
  • Input voltage range: 1.8V to 5.5V
  • Continuous output current: up to 2.4A (PVIN = 2.5V, VOUT = 3.3V)
  • High efficiency: up to 96%
  • 30µA quiescent current maximizes light-load efficiency
  • Selectable bypass power saving mode operation
  • 2.5MHz switching frequency minimizes external component size
  • Fully protected for short-circuit, over-temperature, and undervoltage
  • Small 2.15mmx1.74mm WLCSP


  • Brownout-free system voltage for smart phones and tablet PCs
  • Wireless communication devices
  • 2G/3G/4G RF power amplifiers

tuneProduct Options

Part Number Part Status Pkg. Type Carrier Type MOQ Buy Sample
Active WLCSP-TKCURDL Reel 3000
Active WLCSP-TKCURDL Reel 250


Title language Type Format File Size Date
Datasheets & Errata
star ISL91128 Datasheet Datasheet PDF 1.07 MB
Application Notes & White Papers
Five Easy Steps to Create a Multi-Load Power Solution White Paper PDF 846 KB
AN9208: High Frequency Power Converters Application Note PDF 592 KB
AN1681: Grounding Techniques Application Note PDF 509 KB
AN1684: Nonideality of Ground Application Note PDF 397 KB

memoryBoards & Kits

Part Number Title Type Company
ISL91128IIN-EVZ High-Efficiency Buck-Boost Regulator with 4.5A Switches and I²C Interface Evaluation Board Evaluation Renesas

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