7 ms·

So a USB PD 3.1 device must support 5V 9V 20V 28V 36V and 48V right ? I wonder how much more complicated and costly the power circuitry will get.

Pet_Ant 4y ago
Sure it's more complicated per charger but it's simpler when you look at the range for proprietary chargers that it is replacing. Complexity consolidation.
- scarface74 4y ago
  Thought experiment: grab a random “standard” USB C cable and answer a few questions: - will it charge my MacBook Pro 16” and deliver the full 100W? - will it supply data and if so, at what speed? - can it deliver power and video over USB C and work with my portable secondary display?
  - sovnade 4y ago
    the problem is that there is no "standard" usb-c cable. there's usb 3.0, usb 3.1, usb 3.2, usb 3.2 gen 2, usb-c thunderbolt, etc. this is a major problem they need to figure out imo. edit: or move to a new major version (usb 4.0) and make all new cables do all of that so if you get a 4.0 cable, you know you can use it for everything at once. i have no idea if this is currently the plan or not.
    - scarface74 4y ago
      Obligatory: https://xkcd.com/927/ https://xkcd.com/927/
      - sovnade 4y ago
        hah, i didn't say it was a simple problem to solve :)
    - Vt71fcAqt7 4y ago
      >or move to a new major version (usb 4.0) They're already at USB4 version 2.0
  - seba_dos1 4y ago
    > - will it charge my MacBook Pro 16” and deliver the full 100W? If it's e-marked, then yes. > - will it supply data and if so, at what speed? > - can it deliver power and video over USB C and work with my portable secondary display? If it's not just a USB 2.0 cable, then yes.
    - scarface74 4y ago
      These aren’t rhetorical questions. I didn’t start looking into USB until two years ago when I got a work MacBook. Before then, it had been almost a decade and a half since I had a Mac. - the USB C cable that came with the x86 Macs and most USB C charging cables are power only and don’t support data - many USB C cables that do support data only support data at USB2 speeds and don’t support video over USB - I think some cables can support video over USB C. But only support data at lower speeds than 10Gbps.
      - megous 4y ago
        Yeah, no. There are no non-data Type-C cable assemblies. If you have a C-C cable without at least USB 2.0 data signals wired through, it's not standards compliant: https://megous.com/dl/tmp/6e4e502cb9f6e709.png https://megous.com/dl/tmp/6e4e502cb9f6e709.png
        scarface74 4y ago
        The USB C cable that comes with the MacBook Pro only supports charging https://www.macintoshhowto.com/hardware/why-your-usb-c-cable-may-not-work-to-connect-your-macbooks-together.html https://www.macintoshhowto.com/hardware/why-your-usb-c-cable...
        seba_dos1 4y ago
        It only pretends to be a USB-C cable then.
        seba_dos1 4y ago
  - altairprime 4y ago
    There are four different versions and a wide variety of power choices that each “USB C” cable is permitted to make. So the answer to your question is “it depends”, since 100W support is optional in USB-C cables. (Note: If you change “USB C” cable to “Thunderbolt 3” cable, those choices are all zeroed out. So the answer to that modified question is “yes”, since 100W support is mandatory in Thunderbolt 3 cables.) This will get better over the next year for certified cables that print USB-compliant logos on them, with the end of SuperSpeed branding: https://news.ycombinator.com/item?id=33034530 https://news.ycombinator.com/item?id=33034530 > Branding for certified USB Type-C cables is also being updated. Rather than simply listing their data transfer speeds, cables will also (for the most part) have to list the charging wattage they’re capable of carrying. So a cable can’t just be branded as being a 40Gbps cable as with last year’s guidelines, it’ll now also have to list a charging speed like 60W or 240W. But I’ve never seen the USB logos printed on a cable before, so it remains to be seen whether the reduction in complexity to Gbps/W only is sufficient to persuade cable makers to certify their cables or not.
seba_dos1 4y ago
No. It must support 5V, and optionally can support the rest (and more).
deleted 4y ago
[deleted]
mschuster91 4y ago
No. Nothing of this is mandatory except 5V 100 mA (the old USB 1 baseline), which every device must support - every USB power source must be able to support a dumb load at 5V that consumes 100 mA of current, and every USB power sink can assume that it can safely draw 100 mA of current at 5V. That is why USB PD exists - it allows negotiation between a power source and a power sink to determine the voltage level that the source supplies and the maximum current that the sink can draw before the source shuts down for overcurrent protection. Additionally to that, there also exist a number of legacy current negotiation systems using pull-up and pull-down resistors between GND, Vcc and D+/D- (Qualcomm Quickcharge, Apple's stuff and I believe there is another proprietary Samsung scheme), and there is a legacy negotiation scheme from the USB 2 era that allows 5V at 500 mA. And on top of that, for the higher voltage and amperage ranges, cables carry their own "marker chips" that end up in the USB PD negotiation as well, to prevent dumb cables from overcurrent situation as well - IIRC it's >3A that need marked cables. For device implementers, both on the source and sink (or dual-role) device, there exist a number of specialized ASICs and implementation example circuits that can do all the negotiations required on their own (preconfigured with a separate EEPROM chip or via bootstrap resistors) or in cooperation with a device's microprocessor. There have been a number of high profile fuck-ups along the way (e.g. Nintendo Switch third party docks that passed high voltage to the Switch without negotiating first or the first RPi 4 generation that messed up resistors preventing marked cables from working), but by now the lessons learned from these should have propagated through the industry and the how-to guides.
- xani_ 4y ago
  It's because standard have nightmarish level of complexity for something as simple as "pick a value from list one device provides and maybe change powering if that device signals you need to take less power"
  - megous 4y ago
    That's what the PD standard basically is at core. It tucks on other things, too, like negotiating alternate modes, USB data roles, power roles, role swaps, etc. But the core of the standard is just "here's a list of values, and here's a way to tell the source which value I want to use" + method of communicating + some legacy USB stuff and some simplified alternative methods for power sources without PD chips (resistor pull-ups on CC lines to negotiate between legacy/1.5A/3.0A).
Goz3rr 4y ago
The device only has to support those voltage when it can source the matching power profile (i.e. 140W). But usually if you have to be able to generate two different voltages, it's not much more effort to make three or ten, as long as all the components can deal with the higher voltage.
incanus77 4y ago
This great project blog that I follow has as its latest circuit a USB PD explorer and does a nice job of explaining the protocol: http://www.technoblogy.com/show?3Y8J http://www.technoblogy.com/show?3Y8J
m463 4y ago
I can't help but be reminded of the old-time Radio Shack "universal power adapters". They were a dc power adapter with a switch for voltage 3,6,9,12,... and an assortment of barrel jack power tips of different sizes.

Pet_Ant 4y ago

Sure it's more complicated per charger but it's simpler when you look at the range for proprietary chargers that it is replacing. Complexity consolidation.

scarface74 4y ago
Thought experiment: grab a random “standard” USB C cable and answer a few questions: - will it charge my MacBook Pro 16” and deliver the full 100W? - will it supply data and if so, at what speed? - can it deliver power and video over USB C and work with my portable secondary display?
- sovnade 4y ago
  the problem is that there is no "standard" usb-c cable. there's usb 3.0, usb 3.1, usb 3.2, usb 3.2 gen 2, usb-c thunderbolt, etc. this is a major problem they need to figure out imo. edit: or move to a new major version (usb 4.0) and make all new cables do all of that so if you get a 4.0 cable, you know you can use it for everything at once. i have no idea if this is currently the plan or not.
  - scarface74 4y ago
    Obligatory: https://xkcd.com/927/ https://xkcd.com/927/
    - sovnade 4y ago
      hah, i didn't say it was a simple problem to solve :)
  - Vt71fcAqt7 4y ago
    >or move to a new major version (usb 4.0) They're already at USB4 version 2.0
- seba_dos1 4y ago
  > - will it charge my MacBook Pro 16” and deliver the full 100W? If it's e-marked, then yes. > - will it supply data and if so, at what speed? > - can it deliver power and video over USB C and work with my portable secondary display? If it's not just a USB 2.0 cable, then yes.
  - scarface74 4y ago
    These aren’t rhetorical questions. I didn’t start looking into USB until two years ago when I got a work MacBook. Before then, it had been almost a decade and a half since I had a Mac. - the USB C cable that came with the x86 Macs and most USB C charging cables are power only and don’t support data - many USB C cables that do support data only support data at USB2 speeds and don’t support video over USB - I think some cables can support video over USB C. But only support data at lower speeds than 10Gbps.
    - megous 4y ago
      Yeah, no. There are no non-data Type-C cable assemblies. If you have a C-C cable without at least USB 2.0 data signals wired through, it's not standards compliant: https://megous.com/dl/tmp/6e4e502cb9f6e709.png https://megous.com/dl/tmp/6e4e502cb9f6e709.png
      - scarface74 4y ago
        The USB C cable that comes with the MacBook Pro only supports charging https://www.macintoshhowto.com/hardware/why-your-usb-c-cable-may-not-work-to-connect-your-macbooks-together.html https://www.macintoshhowto.com/hardware/why-your-usb-c-cable...
        seba_dos1 4y ago
        It only pretends to be a USB-C cable then.
        seba_dos1 4y ago
- altairprime 4y ago
  There are four different versions and a wide variety of power choices that each “USB C” cable is permitted to make. So the answer to your question is “it depends”, since 100W support is optional in USB-C cables. (Note: If you change “USB C” cable to “Thunderbolt 3” cable, those choices are all zeroed out. So the answer to that modified question is “yes”, since 100W support is mandatory in Thunderbolt 3 cables.) This will get better over the next year for certified cables that print USB-compliant logos on them, with the end of SuperSpeed branding: https://news.ycombinator.com/item?id=33034530 https://news.ycombinator.com/item?id=33034530 > Branding for certified USB Type-C cables is also being updated. Rather than simply listing their data transfer speeds, cables will also (for the most part) have to list the charging wattage they’re capable of carrying. So a cable can’t just be branded as being a 40Gbps cable as with last year’s guidelines, it’ll now also have to list a charging speed like 60W or 240W. But I’ve never seen the USB logos printed on a cable before, so it remains to be seen whether the reduction in complexity to Gbps/W only is sufficient to persuade cable makers to certify their cables or not.

seba_dos1 4y ago

No. It must support 5V, and optionally can support the rest (and more).

deleted 4y ago

[deleted]

mschuster91 4y ago

No. Nothing of this is mandatory except 5V 100 mA (the old USB 1 baseline), which every device must support - every USB power source must be able to support a dumb load at 5V that consumes 100 mA of current, and every USB power sink can assume that it can safely draw 100 mA of current at 5V. That is why USB PD exists - it allows negotiation between a power source and a power sink to determine the voltage level that the source supplies and the maximum current that the sink can draw before the source shuts down for overcurrent protection. Additionally to that, there also exist a number of legacy current negotiation systems using pull-up and pull-down resistors between GND, Vcc and D+/D- (Qualcomm Quickcharge, Apple's stuff and I believe there is another proprietary Samsung scheme), and there is a legacy negotiation scheme from the USB 2 era that allows 5V at 500 mA. And on top of that, for the higher voltage and amperage ranges, cables carry their own "marker chips" that end up in the USB PD negotiation as well, to prevent dumb cables from overcurrent situation as well - IIRC it's >3A that need marked cables. For device implementers, both on the source and sink (or dual-role) device, there exist a number of specialized ASICs and implementation example circuits that can do all the negotiations required on their own (preconfigured with a separate EEPROM chip or via bootstrap resistors) or in cooperation with a device's microprocessor. There have been a number of high profile fuck-ups along the way (e.g. Nintendo Switch third party docks that passed high voltage to the Switch without negotiating first or the first RPi 4 generation that messed up resistors preventing marked cables from working), but by now the lessons learned from these should have propagated through the industry and the how-to guides.

xani_ 4y ago
It's because standard have nightmarish level of complexity for something as simple as "pick a value from list one device provides and maybe change powering if that device signals you need to take less power"
- megous 4y ago
  That's what the PD standard basically is at core. It tucks on other things, too, like negotiating alternate modes, USB data roles, power roles, role swaps, etc. But the core of the standard is just "here's a list of values, and here's a way to tell the source which value I want to use" + method of communicating + some legacy USB stuff and some simplified alternative methods for power sources without PD chips (resistor pull-ups on CC lines to negotiate between legacy/1.5A/3.0A).

Goz3rr 4y ago

The device only has to support those voltage when it can source the matching power profile (i.e. 140W). But usually if you have to be able to generate two different voltages, it's not much more effort to make three or ten, as long as all the components can deal with the higher voltage.

incanus77 4y ago

This great project blog that I follow has as its latest circuit a USB PD explorer and does a nice job of explaining the protocol: http://www.technoblogy.com/show?3Y8J http://www.technoblogy.com/show?3Y8J

m463 4y ago

I can't help but be reminded of the old-time Radio Shack "universal power adapters". They were a dc power adapter with a switch for voltage 3,6,9,12,... and an assortment of barrel jack power tips of different sizes.