VBUS on nRF52840 in USB-PD high voltage

[John Galvin]

I am designing a battery system with can charge or supply power via a USB-C PD controller. It will operate up to 20V. I want the option to connect this USB-C D+/D- to the nRF52840 for diagnostics & bootloading the firmware.

What do I need to do with VBUS? I'm not powering the nRF52840 directly from VBUS, but I suspect this needs VBUS to be present when the connected to a host or device (I am a DRP) & absent when disconnected.

[John Galvin]

Just to clarify, LTC4411 solution suggested by your AI is too expesive. I was hoping that my PD controller (TPS25751DREFR) would supply a suitable signal, but It doesn't I 24V to 5V regulator seems quite a overkill,but maybe that's the only solution. If so what current is required on VBUS which my system is already powered from VDD?

[Hung Bui]

Hi John, 

VBUS is indeed needed for the USBDETECTED and USBREMOVED event. 

From what I can see in the spec the current of VBUS when USB active is 2.4mA. My understanding is that this is regardless if you power the chip from VBUS or from VDD/VDDH. 

[John Galvin]

Thanks for your input. The TPS25751D required a 5V supply PP5V which is used to power the CC comms duing the initial negotiation. I think I can get the TPS25751D to assert a GPIO signal when a connected & negate when disconnected. I could use this with control a FET fromthe PP5V

[Hung Bui]

Hi John, 
Sounds like a plan. I don't have much experience with USB-PD but I assume you still can communicate via DATA+- instead of CC ?