4 ms·

Prior to USB-PD, USB maxed out at 4.5W, and that was a later addition, originally it maxed out at 2.5W. The USB-PW spec allows for 100W power transfer. There ar

Prior to USB-PD, USB maxed out at 4.5W, and that was a later addition, originally it maxed out at 2.5W. The USB-PW spec allows for 100W power transfer. There are far more modes in USB-C/PW, and they're much higher energy. If all you ever need to deal with is 5V and 0.1-0.9A then there's a much narrower range of failure states.

spookthesunset 9y ago
What voltage is the 100W coming through at? If it is low voltage, that is gonna be a really beefy cable... At 12V that is more than 8 amps. 5v is 20 amps. That is a lot of current to send over a typical USB cable...
- AstralStorm 9y ago
  Yes The cable can get warm. That said, now we use two tiny power wires from PCIe spec to deliver north of 12V 200W.
- CNJ7654 9y ago
  Either 15 or 20V I think
- bri3d 9y ago
  Profile 5 is 20V@5A
  - samhain 9y ago
    They are getting rid of explicit profiles btw...
  - gargravarr 9y ago
    Suffice to say, this makes me very hesitant to connect a USB-C phone (which I don't have, thankfully) to a laptop USB-C charger, because even though they /should/ negotiate the correct voltage, the idea of a bug in the implementation causing the charger to fry my phone, perhaps even setting it on fire in the process, isn't worth the risk. As others note, the poor implementations wind up causing us to use only the adapters shipped with the device in the first place, which is actually a worse situation than with standard USB - right now, I know that I can plug a device into any USB charger and get 5 volts. Amperage may vary considerably, but unless the adapter is a real lemon (and yes, I know those exist), it's not going to kill my phone or burn my house down if I don't get the planetary alignment of adapter, cable and device right.
- Dylan16807 9y ago
  The limit for a normal cable is 3A, the limit for a specialized charging cable is 5A.
- bdonlan 9y ago
  In order to reach 100W, you need to use a special cable that is capable of actively participating in the negotiation process in order to advertise its ability to handle 5A@20V.

spookthesunset 9y ago

What voltage is the 100W coming through at? If it is low voltage, that is gonna be a really beefy cable... At 12V that is more than 8 amps. 5v is 20 amps. That is a lot of current to send over a typical USB cable...

AstralStorm 9y ago
Yes The cable can get warm. That said, now we use two tiny power wires from PCIe spec to deliver north of 12V 200W.
CNJ7654 9y ago
Either 15 or 20V I think
bri3d 9y ago
Profile 5 is 20V@5A
- samhain 9y ago
  They are getting rid of explicit profiles btw...
- gargravarr 9y ago
  Suffice to say, this makes me very hesitant to connect a USB-C phone (which I don't have, thankfully) to a laptop USB-C charger, because even though they /should/ negotiate the correct voltage, the idea of a bug in the implementation causing the charger to fry my phone, perhaps even setting it on fire in the process, isn't worth the risk. As others note, the poor implementations wind up causing us to use only the adapters shipped with the device in the first place, which is actually a worse situation than with standard USB - right now, I know that I can plug a device into any USB charger and get 5 volts. Amperage may vary considerably, but unless the adapter is a real lemon (and yes, I know those exist), it's not going to kill my phone or burn my house down if I don't get the planetary alignment of adapter, cable and device right.
Dylan16807 9y ago
The limit for a normal cable is 3A, the limit for a specialized charging cable is 5A.
bdonlan 9y ago
In order to reach 100W, you need to use a special cable that is capable of actively participating in the negotiation process in order to advertise its ability to handle 5A@20V.