TPS65217: TPS65217 AC/USB Issue

Hi Chun,

Thank you for your interest.
Regarding the first question. You are right, the TPS65217 can be powered with a single supply (Vin, DC adapter). It internally decides whether the AC or USB pin level will be routed to the SYS pin. When you only have one supply, then you don’t receive any benefits by connecting the two pins (AC and USB) together. We recommend to connect Vin to AC (or USB) and connect the unused supply pin to GND.

Regarding your second question. You are correct, as stated in the slva686b you can leave the pins BAT and BAT_SENSE floating. BAT and BAT_SENSE must be connected to each other. If you want to prevent a lockup caused by a brownout on Vin, you can follow the guidelines 3.1 or 3.2 in slva901. To answer your question if you don’t design a RLL resistor you risk a lockup.

I hope this answers your questions.

Regards
Kevin

Chun,

Kevin's advice is correct.

With no battery, you must still short BAT_SENSE to BAT. TS pin is left floating by itself.

BAT should be tied to GND through a light load resistor, RLL (1k-10kOhms), to discharge excess energy on this pin when AC is removed and re-applied quickly. If this cannot happen in your application, RLL can be DNP (not populated) and then BAT/BAT_SENSE will be floating.