What's Inside the USB Power Delivery Profile of the Google Pixel 3 XL's 18W USB-C Power Adapter
The 18W USB-C Power Adapter ships with the Google Pixel 3 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) and the Google Pixel 2 XL (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 ran a subset of power tests for the Google 18W USB-C Power Adapter to generate the following test results.
The USB Power Test App first negotiates a power contract for every PDO supported by the Google 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 Google charger and their OCP thresholds. OCP thresholds for the Google charger are set at about 10-15% above the maximum current levels for the fixed PDO's.
|PDO#1 Fixed: 5V 3A|
|PDO#2 Fixed: 9V 2A|
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 Test App and FLIR thermal imaging tools, we measured the heat emitted by the Google charger as seen in the following temperature heat map graphs for both the 5V, 3A and 9V, 2A PDO's.
The max temperature was observed at 29.5 degree Celsius for the 5V, 3A PDO while the 9V, 2A PDO recorded a max temperature of 56.4 degree Celsius.
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, compliance failures were observed for some of the tests performed for the Google 18W USB-C Power Adapter.
USB-IF High Level Mapping Summary
Test Group Description
BMC Physical Layer Transmitter
BMC Physical Layer Receiver
BMC Phyiscal Layer Miscellaneous
Protocol Specific Primary
Power Source/Sink Primary
TDA.18.104.22.168 BMC PHY TX EYE
TDA.22.214.171.124 BMC PHY TX BIT
TDA.126.96.36.199 BMC PHY RX INT REJ
TDA.188.8.131.52 BMC PHY RX BUSIDL
TDA.184.108.40.206 BMC PHY TERM
TDA.2.2.1 BMC PROT SEQ GETCAPS
TDA.2.2.7 BMC PROT BIST NOT 5V SRC
TDA.2.2.9 BMC PROT GSC REC
TDA.220.127.116.11 POW SRC LOAD P PC
TDA.18.104.22.168 POW SRC TRANS P PC
BMC Eye Diagram
Using the GRL-USB-PD C2 Compliance Test Solution App to further capture the load trace screenshot below, we can also see that the Google 18W USB-C Power Adapter supports different voltage and current levels for charging.
You can also see this review for more details on the power capabilities of the Google Pixel 3 XL.