On-The-Go USB Solution Tames Power Management

Increased data rates and ease of use have fueled the USB interface's popularity for both wired and wireless applications. Designers of mobile devices will be especially interested in a new integrated power solution that conforms to the emerging USB On-The-Go (OTG) specification. Using a high-efficiency charge-pump topology, the AAT3125 regulates output voltage to 5 V and supplies up to 100-mA of output current. Additionally, all voltage-monitoring functionality is integrated to ensure OTG-protocol compatibility.

USB OTG is an addendum to the widely implemented USB 2.0 standard. It was developed to allow mobile devices and peripherals to communicate with each other without the aid of a personal computer. Portable devices and peripherals that conform to the specification circumvent the need for PC control. Instead, they dynamically negotiate a master/slave or "host/peripheral" relationship. By simplifying the device-to-device interface, USB OTG is expected to open up a wide range of applications for mobile devices.

To meet the requirements of USB OTG, dual-role devices must supply a minimum of 8 mA on the 5-V bus. They then maintain compatibility with the existing USB standard. To preserve battery run time, the system also must be able to step up battery voltage to 5 V with maximum efficiency. While running at 1 MHz, the high-efficiency AAT3125 regulates output voltage to 5 V. It ensures a power supply between 8 and 100 mA. The device's high switching frequency allows the use of smaller capacitors. These capacitors contribute to a smaller footprint—a key consideration in mobile-device design.