Other Parts Discussed in Thread: TPS2372
Hi,
My application uses a Non-isolated design. I do not use VCOUT and have terminated it with a 0.1UF capacitor.
A) When VCIN is not powered, that is it being terminated to just a 0.1uF capacitor, The TPS2373-4 chip is able to complete the hardware handshake and enable desired power output of PSE. But without VCIN there is nothing at signal TPH, TPL, BT and PG.
B) Since our application needs to identify PSE class and allocated power, we need TPH/TPL/BT signals and so we have biased VCIN using VDD-Resistor-ZENER(9.3V). But after this operation TPS2373 chip stops responding and does not perform handshaking and is not able to enable power output of PSE. Even after restoring to previous state the TPS2373 chip doesnt seem to work.
This was done in a custom circuit and not EVM. Our circuit doesn't have the isolation transformer or PWM controller but everything around TPS2373 is the same as in EVM. The application performs handshaking, enables PSE power output, An MCU which is powered by a battery and does not draw power from POE or VCOUT power outputs reads TPH/TPL/BT/PG.
Our questions are,
1) Has VDD-Resistor-Zener connection to power VCIN been tested by TI? Would you be able to share a schematics circuit to show how its been implemented in a non-isolated application.
2) If so, what is the bias voltage needed there? Datasheet specifies a voltage above 8.5V is enough.
3)Is there any documented case of TPS2373 going bad when applying VCIN in a non-isolated application?
