Can Qualcomm QC and USB Type-C coexist on the same connector?

Nov 28, 2015

Can Qualcomm QC and USB Type-C coexist on the same connector?

I get this question sometimes, so I wanted to do a quick post to address it. tl;dr : USB Type-C Spec forbids it.

Longer explanation:

Qualcomm’s QuickCharge 2.0 and 3.0 use variable voltage on Vbus in order to get more power over the same USB A-to-microB cables. My Nexus 6, for example, comes with a Motorola Turbo Charger which outputs at 5V, 9V, and 12V. QC 2.0 allows for up to 18W charging over an A-to-microB cable by using the combination 12V * 1.5A.

18W is no slouch, actually, and right now, that’s actually 3W more than the 15W that USB Type-C 3A charging can do.

The difference is that Qualcomm’s solution is very proprietary, and it takes over the D+/D- (usb data) lines for good, so that Type-A port can’t be used to communicate to your PC at the same time you fast charge.

USB Type-C doesn’t have that restriction. You can have a hub with a 3A charging port that also hooks up all the data lines as the negotiation is separate from D+/D-.

When the USB-IF got to specifying Type-C, at the same time, considered higher voltages and much more dynamic power requirements as well. That is when the USB Power Delivery was introduced as well. Power Delivery will be able to handle much higher voltages (up to 20V) and higher currents (up to 5A) in a non-proprietary way.

This section of the Type-C specification 4.8.2 calls out chargers and devices that want to use a proprietary charging method and restricts them specifically from modifying Vbus (which is what QC does to get to 9V and 12V), and from altering roles from source to sink.

The idea is to reduce the confusion that could happen because PD does all of these things in an open and non-proprietary way.

If you’re looking for an explanation why the Nexus 6P and 5X do not support QC of some kind, it’s because of the final line in the section I’ve screenshotted here.

USB Type-C Specification rev 1.2, Section 4.8.2, which forbids methods like QC 2.0 and QC 3.0

Also, any USB Type-C charger that purports to support QC2.0 or QC3.0 out of the same Type-C port is also breaking this section of the spec as well.

Hope this has been helpful!

#USB #TypeC #USBC #Nexus6P #Nexus5X

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