TPS23758: TPS2375x Part selection assistance

Hi,

We are designing a low power PoE PD device around the TPS2375x series and would like some advice on choosing the correct part. We are currently considering the TPS23758 and TPS23755

The PD is a small, low power < 5w device that needs to support both 802.3af and non-standard 24v Passive PoE (Mode B).

The intention currently, is as follows:

1) Use a "Fly-Buck" topology to generate 2 power rails, a 5v 500mA primary regulated output and a secondary 12v ~100mA isolated output via a Wurth 750316819 transformer.

2) Use the Mode B pairs from the Passive 24v supply with the Aux ORing Option 2 "PoE preference" as described in the TPS23758/TPS23755 datasheets and the SLVA306A app report.  The Passive PoE supply will be manually enabled via a jumper to pull up APD, so hot swapping power supplies is not required.

This post https://e2e.ti.com/support/power-management-group/power-management/f/power-management-forum/1167490/tps23758evm-080-use-the-tps23758-as-buck-converter suggests that a sync buck topology is workable with either TPS23758 or TPS23755, so given the requirements above, we would appreciate some advice/suggestions on the correct part to choose.

Thanks in advance,

Neil