Tool/software:
Hi Sir,
if i want to switch between DC adapter and PoE , i need hotswap without reboot. how to do it?
the current approach is to give DC priority and will restart once when switching PoE.
thanks for you support and learn from you.
Hi Tommy,
Thanks for reaching out! The most straight forward way is putting the adapter on the Option 3 side (www.ti.com/.../slva306a.pdf).
If using the adapter on the Option 2 side, you may need to use TPS2373-4. This is PD only chip, and you will need to use a PWM controller chip after it (www.ti.com/.../TPS2373-4EVM-758).TPS2373-4 can turn on auto maintain power signature when adapter is sourcing the load
Making PoE -> adapter will be hitless. Making adapter -> PoE will cause a short term ~80ms PG goes down and hotswap in a 275 - 395 mA current limiting (the power should be limited to less than 12W during the ~80ms). So, after PSE-PD handshake finished, you can disable the PG pin's function to avoid it impact the adapter -> PoE transition. You can also not use PG pin overall, but it needs the PWM chip be able to have a >80ms delay startup or soft start time.
Another way on the Option 2 is using external hotswap like PMP20859 (https://www.ti.com/tool/PMP20859). This circuit has no transition limitation like TPS2373-4 case, but it may need higher cost.
Let me know if you have further questions or concerns.
Best regards,
Diang
