0

I am in the process of designing a fancy USB type c cable (paracord, colourful heat-shrink, coils etc) And I'm worried about resistor values, I don't want to blow my phones port or the charger.

I would like to create a usb 2.0 cable and I think to allow it to be used for fast charging + data I will have to add a 56k pulldown resistor on the D+ and D- lines. is this correct? Does this resistor get added on both sides of the cable, totalling 4 resistors in the cable? Can someone help me with a schematic?

These are the connectors I will be using, one on each end of the cable

With these will I have to remove the resistor from one side?

Peter McKinney
  • 111
  • 1
  • 4
    Is this a phone charger you are trying to make? Where did you get the value of a 56k pulldown? What research have you don into this? If you are trying to build a charger, using D+ and D- lines to control charge rate, then this is a common question we get here, a bit of searching will give you some answers, plus there is loads of information out there about it. This should be a pretty simple task to research, rather than asking us to design it for you. Unless I misread and you are attempting something different? – MCG Aug 10 '18 at 14:58
  • No, just building a cable. Ive looked around but I can find nothing on the cable itself. And the information Ive found on places like mauser/here has been mostly based on building charging systems. – Peter McKinney Aug 10 '18 at 15:17
  • 1
    why would a cable need pulldown resistors? .... i think that you need to do more research – jsotola Aug 10 '18 at 15:33
  • I couldnt find any information... which is why I asked here... cables need resistors in them to allow devices set current values (in the case the power port doesnt have sensing eg not using the CC pin on type c) I would appreciate help as Im new to this, not just google it. [Look at the cable diagram, RA resistors](https://www.digikey.ie/en/articles/techzone/2017/mar/designing-in-usb-type-c-and-using-power-delivery-for-rapid-charging) – Peter McKinney Aug 10 '18 at 15:54
  • 1
    The cable itself doesn't have resistors.... You do need to do a little more research – MCG Aug 10 '18 at 16:14
  • The cable itself, does. Ive since found where. the CC pins need to be pulled up to v+ with a 56k resistor on both sides of a c to c usb 2.0 cable to allow charging. [found here](https://electronics.stackexchange.com/questions/327950/problems-trying-to-wire-a-usb-c-cable) maybe you need more research. Those resistors are used for charger negotiation to stop the device from pulling more than 500ma. – Peter McKinney Aug 10 '18 at 16:21
  • 2
    No. Again, it's not the actual *cable* that has the resistors on it. That answer innyour link does explain the 56k pull ups. But they would be on a PCB on either end of the comms. The answrr mentions the receptacles they go in to get the USB C - USB A connectivity. So yes, you do need more research in general electronics if you still Think the cable itself has pull ups. Are you trying to make a USB C to USB A cable? That was the main reason to be specific for those 56k resistors – MCG Aug 10 '18 at 16:25
  • @PeterMcKinney, the link that you provided describes a cable that is used to connect the phone to a legacy computer port that is limited to a 500mA current output. .... a phone charger should not have such a limitation and it should also contain the necessary circuitry to handshake with the phone to determine the charging current – jsotola Aug 10 '18 at 16:32
  • Resistance of a cable can't "blow up" your phone or your charger. It's just a cable. – Catsunami Aug 16 '18 at 18:24
  • What kind of USB C cable? There are many thing you can put on the other end of a USB C cable – Voltage Spike Aug 20 '18 at 21:47

1 Answers1

4

To begin, a Type-C to Type-C cable doesn't have any resistors. For C-C connections the corresponding gender-defining pull-up and pull-down resistors are placed inside corresponding ports, and CC line just communicates/connects them across the link. The resistors are needed on Type-C end only for "legacy cables", where the other end is legacy Type-A or Type-B. In no case there are resistors on D+ or D- cable lines; again, these "charger signatures" are properties of charger ports.

The cable specifications are freely available on USB.ORG website, in developer/documentation area, as part of one big zip file USB 3.2 package. Some places have re-posted the individual Type-C Specifications.

Ale..chenski
  • 38,845
  • 3
  • 38
  • 103