SLVSEW9B August 2019 – December 2019 TPS66120 , TPS66121
PRODUCTION DATA.
VBUS Overvoltage Protection (OVP) is optional. If VBUS OVP is not required, then the OVP terminal should be tied to ground as shown in Figure 6. VBUS OVP is used to detect voltages on VBUS that exceed a set threshold. Upon detection, the PPHV power path is disabled quickly to help protect components connected downstream of the PPHV terminal. It should be noted that VBUS OVP is not a replacement for VBUS TVS protection which is protecting the VBUS terminal itself.
The VBUS OVP threshold is set by a resistor divider from the VBUS terminal to ground as shown in Figure 5. For this design, R1 and R2 are fixed values to provide VBUS OVP protection at the highest voltage contract level. Using R1 = 432-kΩ and R2 =20-kΩ sets a nominal VBUS OVP threshold of 22.6 V. For some applications, it may be desirable to dynamically change the VBUS OVP level based on the negotiated power contract. One possible way is shown in Figure 7. In this case, the PD controller via GPIO, selects the proper divider ratio to set the VBUS OVP threshold based on the negotiated voltage contract level.