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35W Car Charger

by AT&T

Explore Connectivity Technologies

How the Power Profile Looks Like for the AT&T 35W PD Car Charger Supporting USB Power Delivery

The AT&T retail store is one of the many places to shop for different kinds of mobile/PC accessories and smart devices. From popular brands like Belkin, mophie and Samsung, AT&T also offers its own brand of products such as the AT&T 18W Type-C Wall ChargerAT&T 47W Dual Port Car Charger and AT&T 35W PD Car Charger.

The AT&T 35W PD Car Charger supports USB Power Delivery 2.0 technology for fast charging over the USB Type-C interface through the DC power outlet of your car. This car charger makes use of 15 watts (5 volts @ 3 amps), 27 watts (9 volts @ 3 amps) and 35 watts (15 volts @ 2.33 amps) power profiles to quickly charge tablets and smaller notebook computers like Apple's 11-inch iPad Pro (2018) and MacBook (Early 2016) and phones like the Apple  iPhone XS Max or Android phones such as Google's Pixel 3 XL and the Samsung Galaxy S10 Series.

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

Like many AT&T chargers, the AT&T 35W PD Car Charger has been certified by both AT&T and USB-IF as seen from the USB certification logo on the box. This means that this car charger should have a high degree of compatibility to charge most other USB compliant devices.

It's a good thing that the AT&T 35W PD Car Charger comes with its own USB Type-C to Type-C cable accessory which you won't need to use your own cable with the charger.  

While the AT&T 35W PD Car Charger has only a single USB Type-C connector and in case you want to charge multiple devices, you may look for the  AT&T 47W Dual Port Car Charger which has both a Type-C and Type-A connector.

Using the USB Power Test App from Granite River Labs with the Granite River Labs USB Power Delivery Compliance C2 Tester, we performed the following tests for the AT&T 35W PD Car Charger to find out more on the charger's power capabilities.

The USB Power Test App first negotiates a power contract for every PDO supported by the AT&T 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 AT&T charger and their OCP thresholds. We can see that for the 9V and 15V PDO's, the OCP thresholds above the maximum current levels are very high which should only be around 10-20% for best practices.

PDOOCP (A)%OCP
PDO#1 Fixed: 5V 3A3.18105.9%
PDO#2 Fixed: 9V 3A5.48182.6%
PDO#3 Fixed: 15V 2.33A5.5235.8%

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 for the AT&T 35W PD Car Charger, some compliance failures were observed even though the charger claims to be USB-IF certified so just be careful when using this 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

FAIL

3

PHY_PRIMARY_MISC

BMC Physical Layer Miscellaneous

PASS

4

PROT_PRIMARY

Protocol Specific Primary

FAIL

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

FAIL

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

8

TDA.2.2.2.1

TDA.2.2.2.1 BMC PROT SEQ CHKCAP P PC

FAIL

9

TDA.2.2.2.2

TDA.2.2.2.2 BMC PROT SEQ CHKCAP NOMARK P PC

PASS

13

TDA.2.2.7

TDA.2.2.7 BMC PROT BIST NOT 5V SRC

PASS

15

TDA.2.2.9

TDA.2.2.9 BMC PROT GSC REC

FAIL

16

TDA.2.3.1.1

TDA.2.3.1.1 POW SRC LOAD P PC

PASS

17

TDA.2.3.2.1

TDA.2.3.2.1 POW SRC TRANS P PC

PASS

BMC Eye Diagram


Eye Diagram 

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