7.3.1 Overvoltage Protection on V_{BUS_CON} up to 30-V DC

When the V_{BUS_CON} voltage rises above V_OVP, the internal nFET switch is turned off, removing power from the system side. V_{BUS_CON} can tolerate up to 30-V DC. The response to overvoltage is very rapid, with the nFET switch turning off in less than 100 ns. When the V_{BUS_CON} voltage returns back to below V_OVP – V_{HYS_OVP}, the nFET switch is turned on again after an internal delay of t_{OVP_RECOV} (t_DELAY). This time delay ensures that the V_{BUS_CON} supply has stabilized before turning the switch back on. After t_{OVP_RECOV}, the TPD1S414 turns on the nFET through a soft start. Once the OVP condition is cleared the nFET is turned completely on.

7.3.2 Low R_ON nFET Switch Supports Host and Charging Mode

The nFET switch has a total ON-resistance (R_ON) of 39 mΩ. This equates to a voltage drop of less than 140 mV when charging at the maximum 3.5-A current level. Such low R_ON helps provide maximum potential to the system as provided by an external charger or by the system when in host mode.

7.3.3 ±15-kV IEC 61000-4-2 Level 4 ESD Protection

The V_{BUS_CON} pin can withstand ESD events up to ±15-kV Contact and Air-Gap. An ESD clamp diverts the current to ground.

7.3.4 100-V IEC 61000-4-5 µs Surge Protection

The V_{BUS_CON} pin can withstand surge events up to 100-V open-circuit voltage (V_PP), and 700 W. A precision clamp diverts the current to ground and active circuitry switches OFF the nFET earlier than 100 ns before an overvoltage can get through to V_{BUS_SYS}.

7.3.5 Start-Up and OVP Recovery Delay

The TPD1S414 has a built-in start-up delay. Once the device has been enabled, a time t_DELAY elapses before the charge pump is enabled which turns on the nFET. A manufactured preprogrammed soft start, t_SS, is used when turning on the nFET with the charge pump. Once the device is enabled, these start delays, t_DELAY + t_SS, work together to meet the USB inrush current compliance. Similarly, after an OVP event has occurred, the device waits a time t_{OVP_RECOV} before enabling the charge pump to turn on the nFET. The soft-start, t_SS, is still used when turning on the nFET with the charge pump after an OVP event, making the total time for the nFET switch to turn on after the OVP event t_{OVP_RECOV} + t_SS.

7.3.6 Integrated Input Enable and Status Output Signal

The TPD1S414 integrates an enable signal to control the ON and OFF state of its nFET. The device also integrates an status output signal through the ACK pin which indicates whether or not a fault is occurring on the device. See the Table 2 table to understand the functionality of these pins in all of the TPD1S414's states.

7.3.7 Thermal Shutdown

The TPD1S414 family has an overtemperature protection circuit to protect against system faults or improper use. The basic function of the thermal shutdown (TSD) circuit is to sense when the junction temperature has exceeded the absolute maximum rating and shuts down the device until the junction temperature has cooled to a safe level. When in the thermal shutdown condition, the device asserts a fault by setting the ACK pin to High-Z.

7.4.1 V_{BUS_CON} < V_UVLO

When V_{BUS_CON} is less than V_UVLO, the device is in its unpowered state. The nFET is OFF and the ACK pin is High-Z. In this state, TPD1S414 still provides IEC 61000-4-2 ±15-kV Contact/±15-kV air-gap protection and IEC 61000-4-5 100-V open-circuit surge protection.

7.4.2 V_UVLO < V_{BUS_CON} < V_OVP

When V_{BUS_CON} is greater than V_UVLO and less than V_OVP, the device is in its powered state. In this state, the nFET can be controlled ON and OFF through the enable pin. When the EN pin is Low, the nFET is ON and can be used for both charging and host or OTG mode. While the nFET switch is ON, the ACK pin is held Low. When the enable pin is high, the nFET switch is held OFF and the ACK pin is High-Z. In both the enable and disabled states, the TPD1S414 provides IEC 61000-4-2 ±15-kV contact/±15-kV air-gap protection and IEC 61000-4-5 100-V open-circuit surge protection.

7.4.3 V_{BUS_CON} > V_OVP

When V_{BUS_CON} is greater than V_OVP, the device is in the overvoltage protection sate. In this state, the nFET switch is forced OFF regardless of the state of the enable pin and ACK is set High-Z. V_{BUS_CON} can handle overvoltage protection up to 30 V.

7.4.4 OVP Operation

When the V_{BUS_CON} voltage rises above V_OVP, the internal nFET switch is turned off, removing power from the system. The response is rapid, with the FET switch turning off in less than 100 ns. The ACK pin is set to High-Z when an overvoltage condition is detected and the nFET is turned OFF. This pin can be pulled up through external resistors to indicate an OVP condition. When the V_{BUS_CON} voltage returns below V_OVP – V_HYS-OVP, the nFET switch is turned on again after the internal delay of t_{OVP_Recov}. This delay time ensures that the V_{BUS_CON} supply has stabilized before turning the switch back on. After t_{OVP_Recov}, the TPD1S414 turns on the nFET through a soft start to ensure that the USB Inrush current compliance is met. When the OVP condition is cleared and the nFET is completely turned on, the ACK is reset LOW.

7.4.5 Host/OTG Mode

The TPD1S414's UVLO and OVP voltages are referenced to V_{BUS_CON} voltage. In OTG mode, V_{BUS_SYS} is driving the V_{BUS_CON}. Under this situation, initially V_{BUS_CON} is powered through the body diode of the nFET by V_{BUS_SYS}. Once the UVLO threshold on V_{BUS_CON} is met, the nFET turns on. If there is a short to ground on V_{BUS_CON} the OTG supply is expected to limit the current.

Table 2. Device Operation