The Apple 11-inch iPad Pro (2018) is the first iOS product that uses USB Type-C instead of the Lightning connector while supporting USB Power Delivery 2.0 based charging. This allows the iPad to connect directly over USB Type-C to other third party Power Delivery chargers such as the Google 45W USB-C Power Adapter for rapid charging.
Using the USB Type-C to Type-C cable that shipped with the Apple 11-inch iPad Pro (2018), we plugged in the iPad to the Google 45W USB-C Power Adapter to observe charging. The voltage immediately started off at about 5 volts which quickly increased to about 15 volts. The iPad only began to actually pull current right after hitting 15 volts to charge at around 15 watts (15 volts @ 1 amps). The current then gradually stepped up for the iPad to achieve about 37.5 watts (15 volts @ 2.5 amps) charging with the Google charger. The iPad subsequently pulled lower current after a while to eventually charge at around 30 watts (15 volts @ 2 amps). Click here to download the trace captured by the GRL-A1 power analyzer to see more details.