6 Demonstration of DRP operation with the ISOUSB211 EVM

This section discusses the implementation of an isolated USB Type-C DRP by combining the ISOUSB211 evaluation module (EVM) and TUSB320-LA-EVM.

In Figure 6-1, the ISOUSB211 and TUSB320LAI together form a DRP. A standard peripheral-like mouse or USB flash drive interfaced with the TUSB320-LA-EVM configured as an upstream-facing port emulates a USB Type-C peripheral. The role of this second TUSB320-LA-EVM is only USB Type-A to USB Type-C conversion. When connected in this fashion, side 1 of the ISOUSB211 EVM is powered by the VBUS output of the PC’s USB port. Side 2 is powered by the isolated DC/DC converter present on the ISOUSB211 EVM. The TUSB320LAI configured as a DRP detects the connection of a peripheral and provides a VBUS supply on the USB Type-C cable. The external peripheral (standard flash drive plus the TUSB320-LA-EVM) detects VBUS on the USB Type-C cable, and proceeds to connect.

The peripheral was able to enumerate, and data communication and transfer was successful.

The TUSB320-LA-EVM uses Schottky diodes in the supply path, which drop about 0.7 V. For proper operation in high-speed mode (when using a flash drive), we connected an external power supply (5.5 V) to the DC_IN terminal of the TUSB320-LA-EVM to account for the 1.4-V voltage drop in the VBUS path across two Schottky diodes. This 5.5-V supply was not needed when using a mouse (low-speed operation).

In Figure 6-2, the ISOUSB211 and TUSB320LAI together form a DRP. A standard host (any laptop or PC) interfaced with the TUSB320-LA-EVM configured as a downstream-facing port emulates a USB Type-C host. The role of this second TUSB320-LA-EVM is only USB Type-A to USB Type-C conversion. Side 1 of the ISOUSB211 EVM is powered by an external 5-V power supply, and the isolated DC/DC converter on the ISOUSB211 is disabled. The TUSB320LAI configured as a DRP detects the connection of a host and does not drive the USB Type-C VBUS. The external host (a standard laptop plus the TUSB320 EVM) detects Rd pulldowns on CC pins and drives the VBUS supply. After VBUS is present on the USB Type-C connector, the peripheral connects.

The peripheral was able to enumerate and data transfer was successful.

An additional 5.5-V power supply was necessary for high-speed operation given the voltage drop across Schottky diodes on the TUSB320-LA-EVM, as explained earlier.