![]() ![]() ![]() If you plug a device that doesn’t make a pulldown accessible through the CC wire in the cable, your device will never get power from a USB-C port, and would only work with a USB-A to USB-C cable. The PSU, be it your laptop’s port or a charger, can detect the pulldown (known as Rd) because it keeps a pullup (known as Rp) on the CC line – it then checks if a voltage divider has formed on CC, and whether the resulting voltage is within acceptable range. USB-C power supply expects to sense a certain value pulldown on the CC line before it provides 5 V on VBUS, and any higher voltages have to be negotiated digitally. We’ll also learn about emarkers and the mysterious entity that is VCONN! Today, let’s look at the analog signalling used in USB-C – in part, learn more about the fabled 5.1 kΩ resistors and how they work. However, what’s not as widely known is that there are two protocols used in USB-C for communications – an analog one and a digital one. If you’ve been following along our USB-C saga, you know that the CC wire in the USB-C cables is used for communications and polarity detection. ![]()
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