7.2.1 Design Requirements

In this application example we study the protection requirements for a USB Type-C DRP Port, fully equipped

with USB-PD, and 100W charging. The TPS25751 is used to easily enable a DRP port. Both the CC and SBU

pins are susceptible to shorting to the VBUS pin. With 100W charging, VBUS operates at 20V, requiring the CC

and SBU pins to tolerate 20V DC. With these protection requirements present for the USB Type-C connector, the

TPD4S201 is used.

Table 7-1 lists the TPD4S201 design parameters.

Table 7-1. Design Parameters

DESIGN PARAMETER

EXAMPLE VALUE

VBUS nominal operating voltage

20V

Short-to-VBUS tolerance for the CC and SBU pins

28V

VBIAS nominal capacitance

0.1µF

Dead battery charging

100W

Maximum ambient temperature requirement

85°C

7.2.2 Detailed Design Procedure

7.2.2.1 VBIAS Capacitor Selection

As noted in the Section 5.4 table, a minimum of 28V BUS rated capacitor is required for the VBIAS pin, and a

50V BUS capacitor is recommended. The VBIAS capacitor is in parallel with the central diode clamp integrated

inside the TPD4S201. A forward biased hiding diode connects the VBIAS pin to the C_CCx and C_SBUx pins.

Therefore, when a short-to-VBUS event occurs at 21V, 21V BUS minus a forward biased diode drop is exposed

to the VBIAS pin. Additionally, during the short-to-VBUS event, ringing almost doubles the settling voltage of 21V,

allowing a potential 42V to be exposed to the C_CCx and C_SBUx pins. However, the internal diode clamps

limit the voltage exposed to the C_CCx and C_SBUx pins to around 28V. Therefore, at least a 28V capacitor is

required to avoid the destruction of the VBIAS capacitor during short-to-VBUS events.

A 50V, X7R capacitor is recommended to further improve the derating performance of the capacitors. When the

voltage across a real capacitor is increased, the capacitance value derates. The more the capacitor derates, the

larger the ringing in the short-to-VBUS RLC circuit. The 50V X7R capacitors have great derating performance,

allowing for the best short-to-VBUS performance of the TPD4S201.

7.2.2.2 Dead Battery Operation

For this application, we want to support 100W dead battery operation. When the device is out of battery, dead

battery mode is entered. During dead battery mode, enable the USB PD Controller to receive power and apply

the maximum charging conditions of 20V and 5A. The TPS25751 has a built in LDO to supply the TPS25751

power from VBUS in a dead battery condition.

The OVP FETs of the TPD4S201 remain OFF when unpowered to provide protection in dead battery or

unpowered situations. However, when the OVP FETs are OFF, this isolates the TPS25751s dead battery

resistors from the USB Type-C ports CC pins. A USB Type-C power adapter is required to sense the RD

pull-down dead battery resistors on the CC pins to provide power on VBUS. Since the dead battery resistors of

the TPS25751 are isolated from the USB Type-C connector CC pins, connect the dead battery resistors of the

TPD4S201. Short the RPD_G1 pin to the C_CC1 pin, and short the RPD_G2 pin to the C_CC2 pin.

Once the power adapter sees the dead battery resistors of the TPD4S201, 5V is applied on the VBUS pin. The

pin provides power to the TPS25751, turning the PD controller on, and allowing the battery to begin to charge.

However, this application requires 100W charging in dead battery mode, so VBUS at 20V and 5A is required.

USB PD negotiation is required to accomplish this, so the TPS25751 needs to be able to communicate on the

CC pins. To expose the PD controller to the CC lines, turn on the TPD4S201 in dead battery mode. To turn

on the device, the TPD4S201 is powered by the internal LDO of the TPS25751, the LDO_3V3 pin. When the

TPS25751 receives power on VBUS, the TPD4S201 is turned on simultaneously.

www.ti.com

TPD4S201

SLVSIF2 – JULY 2025

Copyright © 2025 Texas Instruments Incorporated

Submit Document Feedback

15

Product Folder Links: TPD4S201