Hello Xingyun5399,

Pin 6 should be connected to the G pin. This DER did not clearly show that the IC has 2 G pins (Pin 2 and Pin 13) that are internally connected and that pin 6 of T8 should be connected to it. 

You can see this connection more clearly in one of our other DERs, DER-1002: RDR-1002 - 140 W USB PD 3.1 Extended Power Range (EPR) Power Supply using InnoSwitch5-Pro (PowiGaN), HiperPFS-5 and Injoinic USB PD Controller | Power Integrations

I have also included an image of the schematic with that specific trace highlighted for your convenience.

I hope this answers your question. 

Hello Xingyun5399,

To answer your questions,

1. Yes, they are the same.
2. All the other connections should be fine.
3. Yes, you can replace it with the PFS5178 and the design will work but you may encounter lower power factor because the design is not optimized with the PFS5178 chip size in mind.

I hope this helps.

Hello Waer

Thanks for your help

Hello Xingyun5399,

The T pin can be left floating when the shut down mode of the IC is not needed or will not be used. The connection you mentioned from T to REF is also internal so no need to connect them externally. 

You can see this mentioned on page 3 of the datasheet for the HiperPFS-5.

I hope this answers your question.

hello Waer

Thank you for your help.

Because I am reading the Chinese datasheet and it is not written in detail, I will download a citation to read.