USB Power Delivery: Plugging into the Benefits
aptiv.com36 points by mooreds 4 days ago
36 points by mooreds 4 days ago
I've basically stopped buying any portable electronics unless they take USB-C.
Currently travelling with a laptop, watch, toothbrush, eReader, camera, bug-bite treater, and phone - all charging from the same power brick.
I'm guaranteed of getting a replacement cable / charger wherever I am in the world if I need it.
The only slight snag is some cheaper itema refuse to use PD and insist on plain 5V/2A - buy most decent travel chargers have NON-PD ports.
Amusingly, most of the buses I've taken recently also have USB-C ports on them for ad hoc charging. Perhaps one day EVs will use USB-PD-Max rather than CCS :-)
Same!
I've also returned a few USB devices that ship with a USB-A to USB-C cable and ONLY charge in that mode, they also MUST charge with USB-C PD.
The two so far were a therapy light and some Zippo hand warmers. Like, who in the hell would design a device that has a USB-C port on it where only a fraction of chargers will work on it. It feels even worse than proprietary charges, because you see a USB-C port on it and think, oh I have a plug that fits it, and then it doesn't F**ing work. Idiot engineering/product teams, making the world suck with their falsely advertised USB-C ports. If anyone of you are on a team that ever makes this decision, just know that it is a stupid decision, and jump ship when you can.
The thing is, making a 5v-only device PD-compliant is literally one resistor. It costs well under a penny.
It's pure ignorance, not a decision, but the lack of one. Lack of caring, lack of having an actual engineer involved, just slapping an oval-shaped port into a product where a trapezoidal port had been, and blindly thinking that magically makes it spec-compliant.
Or not thinking about the spec at all.
I return these devices too. Lots of them. My e-commerce returns over the last year are probably 50% PD non-compliance, 50% all other defects combined.
It's two resistors, actually. But they cost $0.0003 each (that's 0.03¢, or just around 3,333 of them for US$1) from distributors. Though there appears to be a bit of a stock crunch right now.
So... yeah.
The bigger issue is not really the parts cost, it's the fact that it adds an extra part to the design that has to be purchased and tracked and assembled and blah blah blah. This is the real reason it often gets left off on the bottom-of-the-barrel products. Many times there is no other use for a 5.1kΩ resistor. And it might not even fit well at the cheap sizes (0603 or 0402), and going down to 0201-capable assembly factory flow just for these two resistors is not going to happen.
These companies are not manufacturing the device PCBAs, that is done by dedicated companies such as Flex. The PCBA manufacturing companies have warehouses of different resistors, and 5.1kΩ is extremely common. In fact, most PCB resistor values are quite flexible, to save on SKUs (in practice, to save on loading another carrier on the PnP machine) often if a specific resistor needs a specific value then all (or most of) the other resistors will use that value.
I was speaking a little more towards the AliExpress end of things, which is a sadly high proportion of the devices out there. For the midsize CMs and up, you're right, they've got piles and piles of stuff and don't charge by the reel loaded.
5.1k is a surprising resistor value, a lot of modern designs don't really have anything else in that area. I'm often not able to combine anything with it when I'm cost reducing. 4.7k, sure, but there aren't a lot of those either... 2.2k is just not close enough a lot of the time (or ends up as 1k), and same for 10k. So, sadly, it often does stand alone.
Heh, I would've argued the opposite.
5.1k is about the middle of the generic "some kind of pullup" range of 1k-10k, so it's a perfectly fine option for strapping resistors or for a non-critical I2C bus.
4.7k would of course have been better because it's an E6 value (+-20 via the spec) rather than E24, but it's still a value I would expect any PCBA house to have in stock at all times.
But I agree, 1k or 10k would be the obvious no-brainer. I reckon there's probably a technical reason for it, as it does act as a voltage divider together with the Sink pullup, so perhaps there are some restrictions there with the multiple values it needs to distinguish.
Interesting, thank you. That is an end of the market that I have not seen.
I wonder if PD will cause a comeback of that value as more and more legacy device refreshes move to USB-C plugs.
There's an otherwise decent shortwave radio out there that was originally charged with a micro-usb, then they released a "new" USB-C model...except it will only charge with a 5V brick because they literally just swapped out the ports. Really annoying.
Oh man, please tell me it wasn't the CC GP-7. I have the micro version and have been hemhawwing about updating it.
You mean the CountyComm? If so, I'm 99% certain that radio is a rebranded Tecsun PL-360, which is in fact a 5V. I love Tecsun, but why they would cheap out on the USB-C refresh is beyond me.
I'd imagine that a significant portion of the shortwave radio community is capable of soldering in the two resistors.
Only if the device's consumption is < 2.5W, which is what a USB 2.0 computer USB-A's data port limit is. Anything above that, compliance gets a bit more involved and complicated.
Yes, but that's the case with microUSB as well. In fact, refusing to work with underpowered source is easier with USB-C.
It's certainly not easier. Type-c power sink can advertise USB default, 1.5A or 3A easily. USB default is not necessarily underpowered. You still have to use BC1.2 to see if the source is actually underpowered.
If you're just a microUSB device, you'll also check based on BC1.2. And you can ignore CC/Rp check. It's actually simpler.
I guess you can assume anything advertising itself as USB default is underpowered, but then you'd be wrong.
It sure is. You can just spec it to require a USB-C 7.5W/15W source and then you can gate the operation behind a simple analog circuit and Bob's your uncle. No such way with microUSB until you implement BC1.2, which you don't have to support with USB-C (though it's certainly nice when you do).
> but then you'd be wrong
Not at all, it would just miss signaling it's not compatible with, just like with all sorts of proprietary signaling protocols out there. The point is that with microUSB you have no other way, you have to implement BC1.2 (or some proprietary spec) which is often more complex than a comparator on CC line.
> I've also returned a few USB devices that ship with a USB-A to USB-C cable and ONLY charge in that mode...
By "that mode", do you mean "1.5A @ 5V" permitted by BC, or do you mean "3A @ 20V" permitted by non-type-C PD?
> Like, who in the hell would design a device that has a USB-C port on it where only a fraction of chargers will work on it.
Who in the hell would design a charger that can do Type-C PD but can't do either pre-Type-C PD or BC? Does the charger in question also shit the bed when a USB 1.0 device attempts to draw 100mA @ 5V? I hope not! Were it me, I'd return that crappy thing for a refund.
> By "that mode", do you mean "1.5A @ 5V" permitted by BC
Neither - OP means devices with missing CC resistors which will fail to charge with a compliant PD source. (The A-to-C cable works because it provides 5V Vbus unconditionally.)
The A-to-C cable often does not work because the resistors are supposed to be in there.
So if you are having complete charge failures, try a different cable.
A-C cable assembly always works, CC signal is connected within the cable to Vbus via 56kOhm resistor, but that's only relevant to the downstream port, not to the upstream USB-A power sourcing port which does not have access to the CC signal. Upstream port provides power unconditionally within some limits depending on port type (CDP/DCP/USB3.0/2.0 data port/...).
That's how it's supposed to work, yeah.
But there is some trash out there in the world. A lot of it, actually.
Some naughty cables work with some naughty chargers work with some naughty devices. Postel's Law in action, I guess?
Usually the best place to fix it is by getting rid of the bad cables. Usually.
> Usually the best place to fix it is by getting rid of the bad cables. Usually.
No. There is no USB-C to C cable that will charge a badly implemented device with a standards compliant charger. That is the entire point.
An USB A to C cable is completely standards-compliant and safe, even if it always supplies 5V on the C end - any standards compliant USB-C device should not activate the MOSFET on its Vbus line unless it successfully negotiates via CC.
They mean bad USB-A to C cables with no resistor on CC line. Of course this is broken junk which will work with some devices and won't with others. I've also seen cables with resistors on both CC lines, which is also broken but in a slightly subtler way.