How the Power Capabilities Look Like for the Apple 18W USB-C Power Adapter That Came with the Apple 11-inch iPad Pro (2018)

The 18W USB-C Power Adapter ships with the Apple 11-inch iPad Pro (2018) which is the first iOS product that uses USB Type-C instead of the Lightning connector in the 2018 iPad Pro range. The Apple 18W USB-C Power Adapter supports the common USB Power Delivery profiles of 15 watts (5 volts @ 3 amps) and 18 watts (9 volts @ 2 amps) for charging out. The charger is also compatible with the latest Apple iPhone's like the Apple iPhone XS, iPhone XS Max and iPhone XR as well as iPad Pro's such as the Apple 12.9 inch iPad Pro and 10.5-inch iPad Pro although these products still need to use the typical USB to Lightning cable.

We used the USB Power Test App from Granite River Labs with the Granite River Labs USB Power Delivery Compliance C2 Tester to generate the following test results for the Apple 18W USB-C Power Adapter.

The USB Power Test App first negotiates a power contract for every PDO supported by the Apple 18W USB-C Power Adapter, and increases the load gradually to find the threshold where over current protection (OCP) kicks in and voltage and current start to drop for safety reasons.

The USB Power Test App reports out all the PDO's supported by the Apple charger and their OCP thresholds. OCP thresholds for the Apple charger are set at about 15-20% above the maximum current levels for the fixed PDO's.

PDO	OCP (A)
PDO#1 Fixed: 5V 3A	3.46
PDO#2 Fixed: 9V 2A	2.45

The USB Power Test App from Granite River Labs takes this data to produce an I-V curve which graphically shows the relationship between voltage and current for each PDO. We can observe as the current increases beyond the OCP threshold, the voltage immediately shuts off.

The USB Power Test App can also use the Granite River Labs USB Power Delivery Compliance C2 Tester integrated with the GW Instek APS-7100 programmable AC power supply to compare the charger's power output vs power input so that power efficiency can be measured and compared to regulatory limits from United States of Energy (DOE) Level VI or European Union's CoC Tier 2 requirements. We can repeat the power efficiency tests for different PDO's, current load conditions, and different AC input ranges, allowing us to get a complete picture of power efficiency ranges across all different usage scenarios.

Using the USB Power Delivery Compliance C2 Tester from Granite River Labs to run just a subset of the full USB Power Delivery compliance test suite, no compliance failures were observed for most of the tests performed for the Apple 18W USB-C Power Adapter.

USB-IF High Level Mapping Summary

Sl No	Test Category	Test Group Description	Test Result
1	PHY_PRIMARY_TX	BMC Physical Layer Transmitter	PASS
2	PHY_PRIMARY_RX	BMC Physical Layer Receiver	PASS
3	PHY_PRIMARY_MISC	BMC Physical Layer Miscellaneous	PASS
4	PROT_PRIMARY	Protocol Specific Primary	PASS
5	POWER_PRIMARY	Power Source/Sink Primary	PASS

Result Summary

Sl No	Test ID	Test Name	Test Result
1	TDA.2.1.1.1	TDA.2.1.1.1 BMC PHY TX EYE	PASS
2	TDA.2.1.1.2	TDA.2.1.1.2 BMC PHY TX BIT	PASS
3	TDA.2.1.2.2	TDA.2.1.2.2 BMC PHY RX INT REJ	PASS
4	TDA.2.1.2.1	TDA.2.1.2.1 BMC PHY RX BUSIDL	PASS
5	TDA.2.1.3.1	TDA.2.1.3.1 BMC PHY TERM	PASS
7	TDA.2.2.1	TDA.2.2.1 BMC PROT SEQ GETCAPS	PASS
11	TDA.2.2.7	TDA.2.2.7 BMC PROT BIST NOT 5V SRC	PASS
13	TDA.2.2.9	TDA.2.2.9 BMC PROT GSC REC	PASS
14	TDA.2.3.1.1	TDA.2.3.1.1 POW SRC LOAD P PC	PASS
15	TDA.2.3.2.1	TDA.2.3.2.1 POW SRC TRANS P PC	PASS

BMC Eye Diagram

We also used the GRL-USB-PD C2 Compliance Test Solution App to generate the following load trace that shows the Apple charger supporting different voltage and current levels for charging.

You can also see more details on how the Apple 11-inch iPad Pro (2018) supports USB Power Delivery in this review.