TPS23754: T2P not becoming active when APD is active

Hi Michael,

Thanks for reaching out! May I know if the you connect a plug power supply at RJ45 directly or Option 1 or 2? Is the plug power a DC voltage, how much is it? 

For the APD, it is used for Option 2 adapter. Could you show the APD connection and I can see what voltage pulls it to high?  

Best regards,

Diang 

Hi Diang,

we are using ORing option 1. Here is the schematic:

When plug power is present, the voltage divider provides between 2.0V and 2.4V at the APD-pin.

Best regards,

Michael

Hi Michael,

Thanks for the schematic. 

The oring is more like the Option2. I will take a look and get back to you in 4 business days.

Best regards,

Diang

Hi Michael,

I tested on TPS23754EVM-420, the T2P pin will be low (active low) when you use Option 2 adapter and APD pin is above threshold. Can you show circuit with T2P connection?

Best regards,

Diang

Hi Diang,

here is the complete circuit. The question is: When T2P pin fails to go low, what should I check?

Hi Michael,

Thanks for your full schematic. Is your converter non-isolated since R15 shorts the RTN and isolated ground?  Besides, normally you need the VDD-VSS (or VDD-RTN) voltage > 15V to make the internal logic circuit work, including the T2P function.   

Best regards,

Diang

There are 2 different stuffing options, PD and PSE. This resistor is only stuffed for the PSE option.

My question is, what could be the reason for not having the T2P go low when adapter power is present and the ADP-pin is higher than 1.5V?

Hi Michael,

I am currently working on verification. Will be back for E2E support from Jan 20th. Thanks for your patience. 

Best regards,

Diang

Hi Michael,

Thanks for your patience. 

Michael Gilge said:

My question is, what could be the reason for not having the T2P go low when adapter power is present and the ADP-pin is higher than 1.5V?

Except the faults like over temperature, or transients during startup, shut down, the only reason I could guess now is improper grounding or too low VDD-VSS voltage. Could you help to check when your APD - RTN is > 1.57V meanwhile  

- Your VDD-VSS voltage is higher than 15V

- The DC adapter ground is refer to RTN

Best regards,

Diang