A Closer Look at the Google 45W USB-C Power Adapter USB Power Delivery Behavior

The Google 45W USB-C Power Adapter ships with the Google Pixelbook and supports the common USB Power Delivery profiles of 15 watts (5 volts @ 3 amps), 27 watts (9 volts @ 3 amps), 36 watts (12 volts @ 3 amps), 45 watts (15 volts @ 3 amps), and 45 watts (20 volts @ 2.25 amps).

Using the USB Power Test App from Granite River Labs with the Granite River Labs USB Power Delivery Compliance C2 Tester, we generated the following test results for the Google 45W USB-C Power Adapter to view its power capabilities.

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. Interestingly it is missing both the above mentioned 36 watts (12 volts @ 3 amps) and 45 watts (20 volts @ 2.25 amps) power profiles of the charger. OCP thresholds for the charger are set at about 15% above the maximum current levels for the fixed PDO's.

PDO	OCP (A)
PDO#1 Fixed: 5V 3A	3.48
PDO#2 Fixed: 9V 3A	3.47
PDO#3 Fixed: 15V 3A	3.48

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.

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, we can confirm that the Google 45W USB-C Power Adapter does support all the following PDO's- 15 watts (5 volts @ 3 amps), 27 watts (9 volts @ 3 amps), 36 watts (12 volts @ 3 amps), 45 watts (15 volts @ 3 amps), and 45 watts (20 volts @ 2.25 amps) for charging.

Power Capabilities

Parameter	GetCapabilities
No of Source PDOs
Supply Type #1	Fixed
Peak Current #1	0x0(A)
Voltage #1	0x64(5V)
Max Current #1	0x12C(3A)
Supply Type #2	Fixed
Peak Current #2	0x0(A)
Voltage #2	0xB4(9V)
Max Current #2	0x12C(3A)
Supply Type #3	Fixed
Peak Current #3	0x0(A)
Voltage #3	0xF0(12V)
Max Current #3	0x12C(3A)
Supply Type #4	Fixed
Peak Current #4	0x0(A)
Voltage #4	0x12C(15V)
Max Current #4	0x12C(3A)
Supply Type #5	Fixed
Peak Current #5	0x0(A)
Voltage #5	0x190(20V)
Max Current #5	0xE1(2.25A)

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	PASS
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	PASS

BMC Eye Diagram

Below is a load screenshot captured using the GRL-USB-PD C2 Compliance Test Solution App that shows the Google 45W USB-C Power Adapter  supporting various voltage and current levels for charging.