USB Micro versus USB C type connectors

**Member Since: 8 years (?) starting with a Defy XT
**Phone: New Pixel 4a replacing a Moto G1
**Plan: My Choice with 1G data

My Pixel 4a came with a USB C cable and charger. I seems to charge very fast. Using a magnifying glass on the charger, I noted the output voltages are listed as the usual 5 volts DC (at 3.0 amps) characteristic of all earlier USB connectors but it also listed an output of 9 volts DC (at 2.0 amps). My next stop was Wikipedia to examine the standard pinout of the USB C cable, but that gave no clue as to voltages that might appear on some of the 12 pins on each side of the connector which allow it to be plugged into a device in an “any side up” orientation.

So here are my questions for anyone (no guessing allowed) who has authoritative answers:

  1. Does Google use one of the auxiliary pins on the USB C connector to permit a faster charge rate using 9 volts DC?

  2. If I use one of my older USB chargers that have a USB A connector into which I can connect a patch cable with a USB A on one end and a USB C on the other end, can I use it on the Pixel 4a without fear of damaging the phone?

  3. If the answer to question (1) is no, will I see the same apparent fast charge rate on my new phone if I have an older charger capable of delivering a 3.0 amps output at 5 volts if it can be fitted with a cable having a USB Type A connector on one end and a USB C connector on the other end? (Note: A quick check of several “old” chargers for previous cellphones with chargers having a USB Type A jack for output show current capacities of 800ma to 1.5 amps. Only a charger for a Samsung Tablet shows a current output of 2 amps (5 volts @ 2 amps=10 watts). The Samsung Tablet also seems to charge quickly. So perhaps the 15 watts (5 volts @ 3.0 amps) of my Pixel 4a charger is what is giving these delightfully quick charging results.)

It seems to me that I saw in some Pixel 4a literature a 18w charging capability is available. That is curiously familiar since 9 volts @ 2 amps produces – 18 watts!! Is Google using some of those “extra” pins in the USB C connector to use the connector in a proprietary way to get a fast charge?

There’s nothing proprietary about the fast charging supported by the Pixel. The USB-PD standard support 5V@2A, 12V@1.5A, 12V@3A, 12V@5A, 20V@3A, and 20V@5A (Just because the standard supports this, doesn’t mean all devices do. 60W and 100W charging is usually reserved for laptops that use USB-C). There is the competing fast charging protocol Quick Charge which is owned by Qualcomm and has completely different charging schemes. Google does not support QC on its devices. The latest Samsung devices support both QC and USB-PD.

There are plenty of USB-A to USB-C cables out there. Honestly, If you want a deep read on all of this here’s a great article by one of the experts in this: USB Type-C™’s Configuration Channel | by Benson Leung | Medium

If you still have questions after that, come back and we’ll try to answer them.


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