To USB or Not to USB


USB Type-C: More Power – Part 2

USB Fans,

It’s great when our 33,000+ readers send us email. We feel our friends read and enjoy our blog in addition to our competitors. (Hi Competitors!)

Chris Yokum, USB expert at Total Phase sent me educational email (and one compliment on elephant jokes).  He explains more precisely, more technically what Type C can/will do to deliver power.

I’ve included it verbatim to save me time, and also because I think it’s easier to follow than my actual blog writing.

Type-C with Chris Yokum of Totalphase


From: “Chris Yokum” at Total Phase
To: “Eric Huang”
Sent: Friday, March 18, 2016 9:59:06 PM
Subject: Type-C Default Current

Hi Eric – saw your blog, had a note to provide privately! 🙂

Look at Type-C 1.1 Table 4-13. Putting a 56Kohm pull-up on the DFP’s CC will indicate to the UFP that the DFP (Host) can provide only “Default” power, aka 900mA for USB3.0. Not a mandatory minimum of 7.5W, it’s still a possibility for Type-C to provide 4.5W or 2.5 even..

There’s a possibility to declare higher capability but devices aren’t guaranteed more. There’s possibility to also negotiate higher using PD, but that’s far beyond minimal Type-C..

I’m that comic book store owner on the Simpsons who… ahm.

How are you?


(Chris’s Mobile Phone number deleted to protect the elephants)

On Mar 19, 2016, at 1:00 PM, Chris Yokum
From: “Chris Yokum” at Total Phase

Incredible elephant jokes, btw. thanks!

From: “Eric Huang”
To: “Chris Yokum”  at Total Phase
Sent: Monday, March 21, 2016 7:47:55 PM
Subject: Re: Type-C Default Current

Do you mean that you don’t have to provide the higher power but you can provide the power without PD?   (Text deleted to protect the reader from Eric’s ignorance.  No elephant jokes deleted so no need for concern.)


From: Chris Yokum []
Sent: Monday, March 21, 2016 9:06 PM
To: Eric Huang <>
Subject: Re: Type-C Default Current

Hi Eric,

The fundamental tidbit for this is that “A Type-C connector is legal even if it only provides legacy USB power” – that’s why I emailed about your blog 🙂

You aren’t guaranteed more than a Type-A provided just because it’s Type-C. What Type-C brings is the option itself for higher advertisement (either simply via the pull-up resistor or in more complex cases by PD negotiation) and for the negotiation of complex power scenarios..

The answer to your question is “yes”

A port has an initial power capability advertisement through its pullup resistor (Rp) then (optionally) it can do a PD negotiation further. That initial power could be 15W, but the minimum is much less.

Does that help?



Eric’s Conclusion:  Type-C can provide up to 15W, but apparently isn’t guaranteed to.   It does mean the wall charger you buy with Type C can be rated up to 15W and be relatively inexpensive.  For other sources of charging (like your PC) it can vary depending on the manufacturer’s implementation.  Higher power is communicated through the use of a pull-up resister on the Host side.

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Elephant Jokes

Courtesy of Alex Shishkoff, outstanding FAE at Synopsys

From: Alex Shishkoff
Sent: Friday, March 18, 2016 1:05 PM
To: Eric Huang
Subject: Elephant jokes…
Importance: Low (You got that right)

You probably have these, but it gives me an excuse to type lame jokes.

(First 2 jokes deleted to protect elephants)

Q: What did Tarzan say when he saw a herd of elephants in the distance?
A: “Look, a herd of elephants in the distance!”

Q. What did Tarzan say when he saw a herd elephants wearing sunglasses?
A. Nothing, he did not recognize them.

Q. Why do elephants paint their toenails red?
A. So they can hide in cherry trees.

Q: Why do elephants hide in cherry trees?
A: So they can jump out and stomp on people.

Q: How did Tarzan die?
A: Picking cherries.

Underlined text is text I’ve inserted to improve the flow of the elephant jokes.

As if that was possible.

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