Apple USB-C charger; how does that turn on?

[Beeldbuisje]

While working on my A1707 with defective CD3215 chips (concluded later this board's copper ways are destroyed), I never managed to find out how Apple's original USB-C charger turns on... Does somebody knows this?

When the charger has been plugged in, but disconnected from the laptop, or connected to a non working USB-C port, there's nothing visible on the VBUS output, nor on the CC pins.
Measured with scope as well as with a multimeter. Nothing.
Connecting this charger on a working port, immediately 5V.

What's the trigger to start the 5V on VBUS?

 

[2informaticos]

You can find lot of information on Internet.
Texas Instrument offers good documentation, being famous manufacturer of power supply chips of all kind.
CD3215 chip is made by TI and has exact same layout as TPS65981/2; also TPS65987, if I correctly remember.
Of course, internal firmware makes the diference; even CD3215C00 is not compatible with CD3215B03, for example.

5V output is triggered by hardware; detection being made through CC1/2 lines.
VBUS will not appear if the impedance sees by charger on corresponding CCx line is not expected one.
USB-C charger can deliver more voltages than 5V and 20V.
Software communication with the sink device is needed to establish the correct output voltage.
This data change is known as Power Delivery Protocol.
And all USB-C chargers must comply with it, not only ones from Apple!

Richtek also has a good information for this purpose.

Introduction to Richtek USB Type-C Power Delivery Solutions | Richtek Technology

www.richtek.com