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I am using the TPS25740B(datasheet) as a usb-c PD controller. I am confused why it can only output 60W with receptacle.

From the datasheet:

Later it says:

Question 1: Does this mean current should be limited to 3A solely because the cable connected to the receptable might not be able to handle 5A?

Also, I am a little confused as to how to wire the D+ and D- wires of the usb-c connector.

Question 2: What is the function of the D+ and D- pins on the USB-C connector during charging? Are these pins only used for charging negotiation if some sort of adapter is used?

Question 3: Does applying 2.7V at D+ and D- only advertise 2.4A to apple devices(which should be using the usb-c PD)? If so, then should I short D+ and D- for BC 1.2 DCP which would provide 1.5 A to all devices?

Question 4: On a usb-a port, Is there a way to provide 2.4A to apple devices and >=1.5A to other devices except for using a chip like this: TPS2511(datasheet). Would this also work on usb-c D+ and D-?

Thanks!

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Question 1: Does this mean current should be limited to 3A solely because the cable connected to the receptable might not be able to handle 5A?

Since it doesn't communicate with the cable to ask what it is rated for, they advice you to only use 5A with a captive cable. Otherwise someone could plug in cable only rated for 3A, the cable could report that it doesn't support 5A, but you could damage it because you ignore that signal. If you want 5A, there is probably a more appropriate part that can talk to the ID chip in 5A cables to check that it is safe to supply that much current.

Question 2: Shouldn't these only be necessary if a usb-a->usb-c adapter is used?

Most USB-C cables are not rated for 5A, so this is not a problem specific to USB-A.

Question 3: Does applying 2.7V at D+ and D- only advertise 2.4A to apple devices(which should be using the usb-c PD)? If so, then should I short D+ and D- for BC 1.2 DCP which would provide 1.5 A to all devices?

I think a lot of devices understood that convention, so probably not just Apple devices that would notice the voltage and charge at faster than 1.5A.

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  • \$\begingroup\$ Thanks for the answer. Sorry I was a little vague in question 2. What I meant to ask is: What is the function of the D+ and D- pins on the USB-C connector during charging? Are these pins only used for charging negotiation if some sort of adapter is used? Thanks again. \$\endgroup\$ Commented Jan 6, 2022 at 13:23
  • \$\begingroup\$ @jb0 I think non PD devices still use the resistor method to signal greater than 500mA. Trying my phone, it does draw 1 amp from an old 1 amp iPod charger with a USB A->C cable, so it is checking the voltages over USB-C. Hopefully someone else can confirm. \$\endgroup\$ Commented Jan 6, 2022 at 14:44
  • \$\begingroup\$ thanks for the clarification. \$\endgroup\$ Commented Jan 6, 2022 at 15:28

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