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AT&T's Type-C Wall Charger Offers 18W Fast Charging with USB Power Delivery for Mobile Devices

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Pixel 3 XL

by Google Inc.

Not only a major mobile carrier in the US, AT&T now has its own products supporting USB Power Delivery technology like the AT&T 18W Type-C Wall Charger. The AT&T charger uses USB Power Delivery 2.0 over the USB Type-C port to supply 18 watts of charging. This level of charging is enough for most mobile phones sold today such as the Apple iPhone XS Max or Android phones such as the Google Pixel 3 XL and the Samsung Galaxy S9+. 18 watts output can also provide decently fast charging to tablets like the Apple 11-inch iPad Pro (2018).

Note if you need to charge your iPhone you need to use the Apple USB-C to Lightning Cable.

The label on the packaging shows that the AT&T 18W Type-C Wall Charger has been certified by AT&T as meeting the USB compliance specifications. This means that the charger should have a high degree of compatibility to charge most other USB compliant devices.

The AT&T 18W Type-C Wall Charger has a design that matches well with many smart home devices. 

The AT&T 18W Type-C Wall Charger claims to support these power profiles for charging- 15 watts (5 volts @ 3 amps), 18 watts (7 volts @ 2.57 amps), 18 watts (9 volts @ 2 amps) and 18 watts (12 volts @ 1.5 amps) using USB Power Delivery over USB Type-C.

Like many ac wall chargers, the AT&T 18W Type-C Wall Charger has standard foldable prongs to plug into a ac wall socket.

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 AT&T 18W Type-C Wall Charger.

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

Port1 Plot

The USB Power Test App also reports out all the PDO's supported by the AT&T charger and their OCP thresholds. OCP thresholds for the AT&T charger are set at about 15-20% above the maximum current levels for the fixed PDO's.

PDOOCP (A)
PDO#1 Fixed: 5V 3A3.67
PDO#2 Fixed: 7V 2.57A3.09
PDO#3 Fixed: 9V 2A2.36
PDO#4 Fixed: 12V 1.5A1.75

The USB Power Test App 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.

IV Curve

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 AT&T 18W Type-C Wall Charger.

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


Eye Diagram 

The following load trace was also generated using the GRL-USB-PD C2 Compliance Test Solution App that shows the AT&T charger supporting different voltage and current levels for charging.

We'll see how the AT&T 18W Type-C Wall Charger performs with various USB Type-C devices in the next coming reviews.

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