USB-C Power inlet - Page 1
Forum section: electronics / general

author: wilhe_jo
author_rank: Regular Contributor
timestamp: February 17, 2023, 09:34:16 am
content: Hi!Not sure if this is the right forum, but it's more about DFM and suppliers than other things...I've a product where I'm going to change the power inlet.Having in mind the European USB-C thing and the customer-happiness, I was thinking of transitioning from a Barrel-Jack to a USB-C type power inlet (I use a 5V USB power supply already).Looking for options, I stumbled accross these:https://www.aliexpress.com/item/1005004913934656.htmlhttps://www.aliexpress.com/item/1005004914233591.htmlThe first would reduce assembly time (just clip it in) and the second would be a zero-effort swap because it would match my current mounting hole.Has anyone experience with these?I mean, are they somehow "compliant" (ie. have the 2 resistors) when used as a power-inlet?My hope was to find some USB-C => 8pin cable in order to allow me to implement a proper USB-C power input ... but it seems there are no off-the-shelf solutions around...regards

author: asmi
author_rank: Super Contributor
timestamp: February 17, 2023, 04:05:47 pm
content: Quote from: wilhe_jo on February 17, 2023, 09:34:16 amThey've got to, otherwise there will be no power (USB-C host is not supposed to provide power unless it senses anything on CC lines).Quote from: wilhe_jo on February 17, 2023, 09:34:16 amIf 5V/3A is enough, you can simply add two resistors and call it a day. If you need higher voltage, you will need a USB PD controller.

author: wilhe_jo
author_rank: Regular Contributor
timestamp: February 17, 2023, 10:03:22 pm
content: Hmm... But there're these combinations with USB2 chargers.Are 2 resistors to gnd and do/DM shorted enought for all combinations? 500mA are plenty for my application..Now the question is if these ports source or sink power....73

author: thm_w
author_rank: Super Contributor
timestamp: February 19, 2023, 03:01:27 am
content: Quote from: asmi on February 17, 2023, 04:05:47 pmNot the case, as they'd still work with a USB A to C cable.I just got some of these and there are no resistors inside:https://www.aliexpress.com/item/1005004397896079.htmlYou can kinda see the length is too short for any PCB:Some might exist though. Because its really easy to find the connector with a small PCB attached to it.https://www.aliexpress.com/item/1005004662746306.html

author: thm_w
author_rank: Super Contributor
timestamp: February 19, 2023, 03:04:19 am
content: Quote from: wilhe_jo on February 17, 2023, 10:03:22 pmWhat do you mean, you are powering a non-battery device right? How will your device source power.You could use these to source power, but it would be non-compliant.

author: wilhe_jo
author_rank: Regular Contributor
timestamp: February 21, 2023, 09:44:57 am
content: For my understanding, the CC pins are mandatory for USB-C.If you look eg. athttps://community.silabs.com/s/article/what-s-the-role-of-cc-pin-in-type-c-solution, it shows, that the sources have pull-ups , and sinks pull-downs.Hence, if there are resistors, it does matter if they are connected to vbus or gnd.In addition, there are USB2.0 => USB-C cables. hence, there should be a short between d+/d-.regards

author: thm_w
author_rank: Super Contributor
timestamp: February 22, 2023, 12:17:58 am
content: Quote from: wilhe_jo on February 21, 2023, 09:44:57 amYes they are mandatory for compliant products, but these are cheap adapters which don't have them.Maybe you can find another supplier that does have them. Or build/buy your own board, and figure out a way to panel mount it.https://www.adafruit.com/product/4090

author: aandrew
author_rank: Frequent Contributor
timestamp: February 23, 2023, 01:22:09 am
content: Quote from: wilhe_jo on February 21, 2023, 09:44:57 amThat is correct; if you are expecting something to deliver power into your USB-C receptacle you should have 5k1 between CC1 and ground, and another 5k1 between CC2 and ground. That's all you need for 5V, 2.5A. If you need more, then you need to speak the protocol (and the cable you're using also has to be smarter).QuoteI don't think this is true; if you have a USB-A->USB-C cable, then CC1/CC2 should be pulled down inside the cable. Shorting D+ and D- together is something the power source needs to do to tell the downstream device (i.e. you) that the port you're plugged in to is only for power. There are various resistor pulls and protocol dances you can do to query the port you're plugged in to what it can supply you in terms of juice, but pre-USB-C the downstream device (i.e. the one receiving power) does not have to do anything with D+/D- in order to receive the minimum of 5V, 500mA.

author: thm_w
author_rank: Super Contributor
timestamp: February 23, 2023, 01:28:10 am
content: Quote from: aandrew on February 23, 2023, 01:22:09 amI don't think there are any components inside an A to C cable.An A port will always supply 5V, so there is no need for it.

author: NF6X
author_rank: Unknown
timestamp: February 23, 2023, 01:54:56 am
content: Quote from: thm_w on February 23, 2023, 01:28:10 amThe resistors in the cable are not there to tell the A end to turn on power. They are there to tell the C end how much power it is allowed to draw, and which side of the reversible C connector is wired to the other end of the cable. For example, in a compliant USB 2.0 A to C cable, the cable needs to have the correct pull-up resistor in the C end to tell the C device that it is only allowed to draw 500mA, and also which side of the reversible C plug is connected to the A plug at the other end. If the device is just a FS (12 Mbit/s) device, then it can get away with just connecting to both sets of Dp/Dn pins and not switching based on which CC pin is pulled up. But at the higher rates, and especially at the rates using the high speed lanes, the C device needs to see which CC pin is pulled up to determine which data pins to use.

author: james_s
author_rank: Super Contributor
timestamp: February 23, 2023, 02:15:45 am
content: IMHO USB-C for power is a pain in the butt, it's a solution looking for a problem. At least at low power levels I much prefer a plain old barrel jack. I've been hacking those onto all of my Raspberry Pi boards for years since I had so many problems with crappy/overpriced cables. A barrel jack just works, it's cheaper and more mechanically robust and there is less to go wrong.

author: thm_w
author_rank: Super Contributor
timestamp: February 23, 2023, 02:54:28 am
content: Quote from: NF6X on February 23, 2023, 01:54:56 amYeah you are right.It has the one "Rp" resistor from CC to Gnd:https://www.chromium.org/chromium-os/cable-and-adapter-tips-and-tricks/That would explain those cheap USBC connectors with boards on them.

author: NF6X
author_rank: Unknown
timestamp: February 23, 2023, 04:55:05 am
content: A few years ago when I was developing a USB 2.0 device with a type C receptacle at the day job, I ordered several different USB 2.0 A to C cables from DigiKey for compatibility testing. I did find one of them was noncompliant, without the resistor.

author: aandrew
author_rank: Frequent Contributor
timestamp: February 23, 2023, 07:10:41 pm
content: Quote from: thm_w on February 23, 2023, 01:28:10 amYou are of course correct; I was thinking of those USB-C to USB-A "converter" dongles which do have the CC pulldowns since they are plugging in to a USB-C upstream port.