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TPS25740B: Negotiation failed with voltage limited to 15V

Ue
Genius 16465 points
Part Number: TPS25740B

Hi all

I have this question for the TPS25740BEVM, here is what I am doing:

  • configure the board to 18W: 
  • Psel on position P4 -> 36W, PCTRL shunt installed -> PMAX = PSEL/2
  • keep default configuration: HIPWR on H2 position -> 5V, 9V, 15V, 20V

Source cap is advertised as expected, with 18W Max power:

and iPad pro (last gen) select Pos 3 and charges with 18W, all OK.

 

Since I know my power supply will limit available voltage to max 15V, I modify the configuration such that

  • HIPWR on position H4 -> 5V, 9V, 12V, 15V and IMAX = 3A

Source cap is advertised as expected, with 18W Max power and expected voltages modified:  

But It seems the iPad Pro cannot get to negotiate a power:

 

And what I noticed is that as soon as the iPad Pro makes a request for a higher power contract, there's a hard reset occuring and the cycle starts over:

 

Is that a bad configuration on my side or some sort of incompatibility? 

I am looking forward to your feedback.

Best regards

Ueli