STUSB4500 – I²C Pullup with No VBUS/VDD Applied

[JBean-IUP]

Hello,

I am currently designing a battery-powered device that incorporates the STUSB4500. I have a question regarding the I²C pins: specifically, whether it is safe for these pins to be pulled up (via the system microcontroller’s pull-ups) when no voltage is present on VBUS or VDD.

In my design, the primary microcontroller can be powered on even when the USB power is absent, which means the I²C lines would be driven high before VBUS or VDD is applied to the STUSB4500. I have reviewed the datasheet, but it does not clearly state whether the operating or maximum ratings for the I²C pins depend on VDD. My assumption is that it should be acceptable, but I wanted to confirm to avoid any potential issues.

Any guidance or confirmation you can provide would be greatly appreciated. Thank you for your time and assistance.

Thanks!

[TDK]

Datasheet says they're pulled down when VDD is not present. Probably this is by a protection diode in which case the system isn't going to be pulling them up without powering VDD. Backpowering through protection diodes should be avoided.