Other Parts Discussed in Thread: TL5209
We are working on our second AM335x board design using a PMIC TPS65217. The first design used a TPS65217B for DDR2 and we used RTC functionality for PMIC Power Enable. Our new design has DDR3 so we are using a TPS65217C and do NOT use RTC functionality or RTC-only mode per the "AM335x Schematic Checklist" RTC section (RTC feature disabled), the TPS65217C has pin 9 PWR_EN pulled to 1.8v via 10k.
for the most part we have had good luck with these designs. The new design is very similar to the BBB (except for RTC disabled). We have had some TPS65217 modules go bad with VSYS (pins 7&8) usually outputting .8 to 1v. If we isolate the VSYS by disconnecting the VIN loads the output does not change. Also, after this happens with the VSYS and VIN isolated, if I tie 5v to the VIN connections the outputs do not come up. It's like the module no longer responds. We have six 10uf caps on the VIN inputs located around the TPS65217 close to each of the input pins. I noticed that BBB uses only four 10uf caps. I've noticed that if a board is repetitively power cycled, thats when the problem seems to appear. I am curious if I have to much capacitance on the VSYS output? Also, same as the BBB, there is a TL5209 regulator being supplyed by the VSYS output. This schematic design was reviewed by TI engineering. So far, we have had four of the new board prototypes and on two of them the TPS65217C has appeared to have died.
As this design is still a prototype, I'm looking for whatever I can to make it more robust, any ideas?
Thanks,
Brian Weir