The AT43USB380 is a straightforward upgrade of the AT43USB370 Host/Function Processor to support the USB 2.0 On-The-Go (OTG) specification. It can operate either as a single-chip Host/Function Processor or if used in conjunction with an external Atmel Charge Pump, as a full OTG solution. The AT43USB380 is functionally equivalent to the AT43USB370 as a Host/Function Processor and can be used in place of the AT43USB370 in the existing AT43USB370 design with minor hardware modifications. The pinout differences between the AT43USB370 and the AT43USB380 are due to the inclusion of the on-chip OTG interface in the AT43USB380. To support OTG functionality, an external Charge Pump has to be connected to the OTG interface of the AT43USB380, as shown in Figure 1 on page 7. The external Charge Pump serves in the following two capacities: 1. As a power source to the downstream USB devices. 2. As a signaling interface during the OTG session negotiation upon connection. From the hardware standpoint, the AT43USB380 is equivalent to the AT43USB370 with the following exceptions: