8.3.1 4-Channels of Short-to-V_BUS Overvoltage Protection (CC1, CC2, SBU1, SBU2 Pins): 24-V_DC Tolerant

The TPD8S300 provides 4-channels of Short-to-V_BUS Overvoltage Protection for the CC1, CC2, SBU1, and SBU2 pins of the USB Type-C connector. The TPD8S300 is able to handle 24-V_DC on its C_CC1, C_CC2, C_SBU1, and C_SBU2 pins. This is necessary because according to the USB PD specification, with V_BUS set for 20-V operation, the V_BUS voltage is allowed to legally swing up to 21 V, and 21.5 V on voltage transitions from a different USB PD V_BUS voltage. The TPD8S300 builds in tolerance up to 24-V_BUS to provide margin above this 21.5 V specification to be able to support USB PD adaptors that may break the USB PD specification.

When a short-to-V_BUS event occurs, ringing happens due to the RLC elements in the hot-plug event. With very low resistance in this RLC circuit, ringing up to twice the settling voltage can appear on the connector. More than 2x ringing can be generated if any capacitor on the line derates in capacitance value during the short-to-V_BUS event. This means that more than 44 V could be seen on a USB Type-C pin during a Short-to-V_BUS event. The TPD8S300 has built in circuit protection to handle this ringing. The diode clamps used for IEC ESD protection also clamp the ringing voltage during the short-to-V_BUS event to limit the peak ringing to around 30 V. Additionally, the overvoltage protection FETs integrated inside the TPD8S300 are 30-V tolerant, therefore being capable of supporting the high-voltage ringing waveform that is experienced during the short-to-V_BUS event. The well designed combination of voltage clamps and 30-V tolerant OVP FETs insures the TPD8S300 can handle Short-to-V_BUS hot-plug events with hot-plug voltages as high as 24-V_DC.

The TPD8S300 has an extremely fast turnoff time of 70 ns typical. Furthermore, additional voltage clamps are placed after the OVP FET on the system side (CC1, CC2, SBU1, SBU2) pins of the TPD8S300, to further limit the voltage and current that is exposed to the USB Type-C CC/PD controller during the 70 ns interval while the OVP FET is turning off. The combination of connector side voltage clamps, OVP FETs with extremely fast turnoff time, and system side voltage clamps all work together to insure the level of stress seen on a CC1, CC2, SBU1, or SBU2 pin during a short-to-V_BUS event is less than or equal to an HBM event. This is done by design, as any USB Type-C CC/PD controller will have built in HBM ESD protection.

Figure 29 is an example of the TPD8S300 successfully protecting the TPS65982, the world's first fully integrated, full-featured USB Type-C and PD controller.

Figure 29. TPD8S300 Protecting the TPS65982 During a Short-to-V_BUS Event

8.3.2 8-Channels of IEC 61000-4-2 ESD Protection (CC1, CC2, SBU1, SBU2, DP_T, DM_T, DP_B, DM_B Pins)

The TPD8S300 integrates 8-Channels of IEC 61000-4-2 system level ESD protection for the CC1, CC2, SBU1, SBU2, DP_T (Top side D+), DM_T (Top Side D–), DP_B (Bottom Side D+), and DM_B (Bottom Side D–) pins. USB Type-C ports on end-products need system level IEC ESD protection in order to provide adequate protection for the ESD events that the connector can be exposed to from end users. The TPD8S300 integrates IEC ESD protection for all of the low-speed pins on the USB Type-C connector in a single chip. Also note, that while the RPD_Gx pins are not individually rated for IEC ESD, when they are shorted to the C_CCx pins, the C_CCx pins provide protection for both the C_CCx pins and the RPD_Gx pins. Additionally, high-voltage IEC ESD protection that is 24-V DC tolerant is required for the CC and SBU lines in order to simultaneously support IEC ESD and Short-to-V_BUS protection; there are not many discrete market solutions that can provide this kind of protection. The TPD8S300 integrates this type of high-voltage ESD protection so a system designer can meet both IEC ESD and Short-to-V_BUS protection requirements in a single device.

8.3.3 CC1, CC2 Overvoltage Protection FETs 600 mA Capable for Passing VCONN Power

The CC pins on the USB Type-C connector serve many functions; one of the functions is to be a provider of power to active cables. Active cables are required when desiring to pass greater than 3 A of current on the V_BUS line or when the USB Type-C port uses the super-speed lines (TX1+, TX2–, RX1+, RX1–, TX2+, TX2–, RX2+, RX2–). When CC is configured to provide power, it is called VCONN. VCONN is a DC voltage source in the range of 3 V-5.5 V. If supporting VCONN, a VCONN provider must be able to provide 1 W of power to a cable; this translates into a current range of 200 mA to 333 mA (depending on your VCONN voltage level). Additionally, if operating in a USB PD alternate mode, greater power levels are allowed on the VCONN line.

When a USB Type-C port is configured for VCONN and using the TPD8S300, this VCONN current flows through the OVP FETs of the TPD8S300. Therefore, the TPD8S300 has been designed to handle these currents and have an RON low enough to provide a specification compliant VCONN voltage to the active cable. The TPD8S300 is designed to handle up to 600 mA of DC current to allow for alternate mode support in addition to the standard 1 W required by the USB Type-C specification.

8.3.4 CC Dead Battery Resistors Integrated for Handling the Dead Battery Use Case in Mobile Devices

An important feature of USB Type-C and USB PD is the ability for this connector to serve as the sole power source to mobile devices. With support up to 100 W, the USB Type-C connector supporting USB PD can be used to power a whole new range of mobile devices not previously possible with legacy USB connectors.

When the USB Type-C connector is the sole power supply for a battery powered device, the device must be able to charge from the USB Type-C connector even when its battery is dead. In order for a USB Type-C power adapter to supply power on V_BUS, RD pull-down resistors must be exposed on the CC pins. These RD resistors are typically included inside a USB Type-C CC/PD controller. However, when the TPD8S300 is used to protect the USB Type-C port, the OVP FETs inside the device isolates these RD resistors in the CC/PD controller when the mobile device has no power. This is because when the TPD8S300 has no power, the OVP FETs are turned off to guarantee overvoltage protection in a dead battery condition. Therefore, the TPD8S300 integrates high-voltage, dead battery RD pull-down resistors to allow dead battery charging simultaneously with high-voltage OVP protection.

If dead battery support is required, short the RPD_G1 pin to the C_CC1 pin, and short the RPD_G2 pin to the C_CC2 pin. This connects the dead battery resistors to the connector CC pins. When the TPD8S300 is unpowered, and the RP pull-up resistor is connected from a power adaptor, this RP pull-up resistor activates the RD resistor inside the TPD8S300. This enables V_BUS to be applied from the power adaptor even in a dead battery condition. Once power is restored back to the system and back to the TPD8S300 on its VPWR pin, the TPD8S300 removes its RD pull-down resistor and turn on its OVP FETs within 3.5 ms to guarantee the RD pull-down resistor inside the CC/PD Controller is exposed within 10 ms. This is by design, because if the RD pull-down resistor is not exposed within 10 ms, the power adaptor can legally interpret this behavior as a port disconnect and remove V_BUS.

If desiring to power the CC/PD controller during dead battery mode and if the CC/PD Controller is configured as a DRP, it is critical that the TPD8S300 be powered before or at the same time that the CC/PD controller is powered. It is also critical that when unpowered, the CC/PD controller also expose its dead battery resistors. When the TPD8S300 gets powered, it exposes the CC pins of the CC/PD controller within 3.5 ms. Once the TPD8S300 turns on, the RD pull-down resistors of the CC/PD controller must be present immediately, in order to guarantee the power adaptor connected to power the dead battery device keeps its V_BUS turned on. If the power adaptor sees any change to its CC voltage for more than 10 ms, it can disconnect V_BUS. This removes power from the device with its battery still not sufficiently charged, which consequently removes power from the CC/PD controller and the TPD8S300. Then the RD resistors of the TPD8S300 are exposed again, connect the power adaptor's V_BUS to start the cycle over. This creates an infinite loop, never or very slowly charging the mobile device.

If the CC/PD Controller is configured for DRP and has started its DRP toggle before the TPD8S300 turns on, this DRP toggle is unable to guarantee that the power adaptor does not disconnect from the port. Therefore, it is recommended if the CC/PD controller is configured for DRP, that its dead battery resistors be exposed as well, and that they remain exposed until the TPD8S300 turns on. This is typically accomplished by powering the TPD8S300 at the same time as the CC/PD controller when powering the CC/PD controller in dead battery operation.

If dead battery charging is not required in your application, connect the RPD_G1 and RPD_G2 pins to ground.

8.3.5 3-mm × 3-mm WQFN Package

The TPD8S300 comes in a small, 3-mm × 3-mm WQFN package, greatly reducing the size of implementing a similar protection solution discretely. The WQFN package allows support for a wider range of PCB designs. Additionally, the pin-out of the TPD8S300 was designed to optimize routing with the TPS6598x family of USB Type-C/PD controllers.

Table 1. Device Mode Table