Hello, my name is Matt [INAUDIBLE]. I'm a marketing engineer at Texas Instruments Marketing System Connectivity Products. In this video, I will briefly introduced the nine-volt fast-charging protection application for the TS3USB3000 switch. Smartphones, laptops, portable electronic point-of-sale devices, cameras, drones, and other mobile devices are adopting larger and larger batteries. These batteries can hold more charge and extend the battery life of the products.

Regular charging adapters convert AC voltage to 5 volts, but new charging adapters convert to a higher power, which enables faster charging. There are several proposed methods from different manufacturers to implement faster charging. But the common theme is that the higher input voltage is required at the power connector.

Higher input voltage allows more power into the system. Typical values include 5, 9, or 12 volt output levels, depending on the adapter capability. The adapter voltage default setting is the usual 5 volt VBUS level. But signaling on the D-plus, D-minus data lines between the external adapter and the mobile device can negotiate the adapter output higher, as needed. The charging IC or MCU in the system controls this signaling so that the adapter voltage only goes to the appropriate level.

Typically, when inserting the USB connector, you need a USB switch to transmit data between the microcontroller or MCU and a charger like the the TIBQ25890. These switches are also an integrated solution which saves board space and simplifies signal routing on your board. Upon first connection, the MCU has control of the D-plus, D-minus data lines and will detect whether it is a charger or a USB attachment.

TI provides multiple USB switches that cover a wide spectrum in terms of configuration, voltage ranges, on resistance, and bandwidth. Since fast charging generally operates at 9 volts and the MCU cannot tolerate high voltages, it becomes crucial that the MCU is never exposed to 9 volts. However, there are instances where the MCU could potentially be exposed to 9 volts.

The USB connector has four pins-- VBUS, D-minus, D-plus, and ground, shown from right to left in this figure. After negotiating the fast charged state, the VBUS, will now be at 9 volts. Here, the USB connector is inserted to the receptacle. However, if it is removed at an angle, it might cause the VBUS pin to short with the D-minus pin of the connector.

Here is a block diagram that shows the result of what happens if there is no USB switch for protection. If there is a dedicated charging port connected, the MCU communicates with the charger that it can negotiate for a fast charge at 9 volts. However, if the VBUS pin shorts with the D-minus pin of the connector, the MCU would be exposed to the 9 volts and be damaged.

However, the TS3USB3000 switch can tolerate 9 volts and provides an elegant solution to this problem. If a charger is connected to the USB port, the MCU will detect this and toggle the select pin to the charger. The MCU will then communicate to the charger that it can handle fast charge with VBUS at 9 volts. Now, if there's a short between the VBUS and D-minus pins, the MCU is protected from this.

This slide shows the same application in a slightly different layout. The charger can also be placed before the switch, while the switch toggles between the MCU and a Universal Asynchronous Receiver Transmitter, or UART. The mode of operation is very similar. When a charger is connected to the USB port, the MCU will detect that a dedicated charging port is attached. The MCU will then pull the output-enabled pin high to disable the switch.

The MCU then communicate to the charger that it can negotiate for a fast charge with VBUS at 9 volts. Since the switch is disabled, the MCU and UR will still be protected, even if there's a short circuit at the connector port. In summary, the TS3USB3000 switch serves two purposes. One, it switches between the host and the charger, and two, it protect the MCU at five to nine volts.

For the first case, any USB switch can be used, depending on what kind of bandwidth and on resistance that the customer wants. But for the second case, only the TS3USB3000 can protect the MCU in case there's a short. For more information, please see the following resources.