[beagleboard] VIO, Sitara B15 & B5 voltage levels (Gerald)

Hi All (Gerald),

A bit confused about the differences between the BBW and BBB Sitara balls B15 and B5 voltage levels. Reviewing the schematic for the BBW it appears PORZ (B15) is being driven from the TPS65217B pin PGOOD (26) and PGOOD's power supply source VIO is at 3.3v. While on the Sitara RTC_PORZ (B5) is being driven at 1.8 v due to the resistor divider R141 and R18. My understanding from reading the TRM on the Sitara is that both B15 and B5 are 1.8v level pins.

Now on the BBB, both B15 and B5 on the Sitara are being driven directly from the TPS65217C who's VIO is at 1.8v and this all makes sense.

Any help in clarifying my confusion would certainly help.

We're in the process of bringing up our new custom board based on the BBB and have burned up a Sitara because we pushed 3.3v into the VIO pin of the TPS65217C and therefore killed the Sitara via B15 and B5.

Thanks Gerald.

Never mind again. After digging deeper into the TRM and referring to note 11 for VDDSHV6 (page 42), that power supply can be 3.3v and therefore B15 is happy at 3.3v. On the other hand RTC_PORZ can only be at 1.8 (VDDS_RTC). I understand fully now and the confusion between the BBW and BBB is gone.

Again, thank you Gerald and team for all the great work.

Ross

Glad you figured it out.

Gerald