Table 3. Design Parameters

8.2.2.1 USB V_BUS Voltage Range

The USB V_BUS voltage range for a USB device operates between a minimum of 4.4 V and a maximum of 5.5 V (Legacy USB has a maximum of 5.25 V, but the new USB Type C standard raised the maximum to 5.5 V). The TPD1S414 is designed to operate with a V_{BUS_CON}, V_{BUS_SYS} voltage between 3.5 V and 5.9 V. This range exceeds the requirements for USB V_BUS, allowing this device to be used in any USB system. Therefore, no special voltage precautions are necessary when adding TPD1S414 to a USB system.

8.2.2.2 USB V_BUS Operating Current

In this application example, a V_BUS current of 3 A is required. With the addition of the new USB Type C Standard, the VBUS operating current can vary anywhere from 0.5 A to 3 A, depending on the current capability advertised by the source on the CC pin. TPD1S414 is designed to operate up to a maximum of 3.5 A of current, allowing it to be used with the new USB Type C connector. TPD1S414 also has a low RON of 39 mΩ (typical), 50 mΩ (maximum), allowing for excellent thermal performance and low voltage drop across the switch at 3 A.

8.2.2.3 V_{BUS_CON} and V_{BUS_SYS} Capacitance

The USB standard requires a minimum capacitance of 1 µF on V_BUS and allows for a maximum capacitance of 10 µF on a USB device. The minimum capacitance is to reduce inductive spiking on V_BUS when disconnecting the charging cable, and the maximum capacitance is to put a limit on how much a device can drop the V_BUS rail of its host when being hot-plugged into the system. This corresponds to having a typical capacitance of 1 µF on V_{BUS_CON} for a USB system, but higher capacitance up to 10 µF can be used. No more than 10 µF must be put on V_{BUS_CON} to ensure the USB specification is not violated. If more capacitance is required, place this on the V_{BUS_SYS} pin. TPD1S414 turns on its nFET switch with a soft start to help pass USB in-rush compliance, so it is recommended to place bulk capacitance on the V_{BUS_SYS} pin. External capacitors added to the V_{BUS_CON} pin must be placed as close to the V_{BUS_CON} pin as possible, and likewise external capacitors added to the V_{BUS_SYS} pin must be placed as close to the V_{BUS_SYS} pin as possible.

8.2.2.4 IEC 61000-4-5 100-V Open-Circuit Surge

The IEC 61000-4-5 standard specifies the lightning and industrial surge model. Power lines like the V_BUS line on the USB port are subject to switching and lightning transients. Power supply switching transients can enter the system due to capacitor bank switching on the rail, minor load switching on the system and various system faults like arcing to the grounding system of the installation. Direct lightning to the outer installations cause an overvoltage condition on the V_BUS line. In the event of an overvoltage condition, the OVP block of the processor or the protection circuitry turns off isolating the system from these transients. Abruptly turning off the load, causes a further ripple due to the inductive nature of the charging cable. End systems require protection against these transients. These transients have greater energy than the ESD events. Systems cannot be protected from these transients using simple ESD diodes. The TPD1S414 has a precision trigger and precision clamping circuit that ensures a DC tolerance of 30 V while suppressing surge voltage up to 100 V under 35 V. Figure 11 shows the performance of TPD1S414 in the powered-down state under an 100-V surge pulse.