How the USB Power Delivery Profile Looks Like for the Google Pixel 2 XL's 18W USB-C Power Adapter

The 18W USB-C Power Adapter ships with the Google Pixel 2 XL and supports the common USB Power Delivery profiles of 15 watts (5 volts @ 3 amps) and 18 watts (9 volts @ 2 amps). Note this 18W charger is different from the original charger shipped with the original Google Pixel (seen in this review) although still supports the same power profiles.

Using the USB Power Test App from Granite River Labs with the Granite River Labs USB Power Delivery Compliance C2 Tester, we generate the following test results for the Google 18W USB-C Power Adapter to see how this charger supports power.

The USB Power Test App first negotiates a power contract for every PDO supported by the Google charger, 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 Google charger and their OCP thresholds.

PDO	OCP (A)	%OCP
PDO#1 Fixed: 5V 3A	3.29	109.6%
PDO#2 Fixed: 9V 2A	2.31	115.3%

The USB Power Test App from Granite River Labs also produces 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, some compliance failures were observed for the Google 18W USB-C Power Adapter.

Result Summary

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

BMC Eye Diagram

Looking at the load screenshot captured from the GRL-USB-PD C2 Compliance Test Solution App, we can see that the 18W USB-C Power Adapter  supports different voltage and current levels for charging.