USB-C PD controller with USB3.1 Gen 1 mux support - Page 1
Forum section: electronics / projects

author: jars121
author_rank: Regular Contributor
timestamp: December 20, 2020, 05:01:08 am
content: Hi everyone,I'm trying to incorporate a USB-C connector into an existing design, which will both support PD (detailed below) and USB3.1 Gen 1 (5Gbps) data. The board has a DC barrel jack which accepts 7-22V (this will/can be adjusted to suit the requirements of the USB-C PD controller as discussed below).What I'm trying to achieve, is the ability for the USB-C port to act as a secondary power input, such that the board can operate with a suitable USB-C source/charger if the DC barrel jack isn't used. If powered by an external USB-C source, the USB3.1 Gen 1 (5Gbps) is still supported, with the board still acting as the host. If the DC barrel jack is used, the USB-C port acts as a DFP/host, to allow for USB accessories (e.g. adapters, storage, etc.). When acting as a DFP/host, the USB-C port should provide VBUS, but it can be limited to 5V, rather than the full 20V range of the USB-C PD standard. At this stage I'm not sure about VCONN; if I can find a solution which provides internal FETs for VCONN with autonomous CC switching then I'll happily utilise it, but I don't think VCONN is a hard requirement at this stage.Summarising the high-level requirements as follows:When the DC barrel jack is not powered and a USB-C source is attached, the board should operate from Dead Battery mode (assuming the source can provide the minimum PDO of 45W)If the DC barrel jack is powered and a USB-C sink or accessory is attached, the device should able to provide 5W (the amount of current is to be determined)The board should be able to accommodate the scenario whereby the DC barrel jack is powered and a USB-C source is attached. I.e. the board shouldn't explode if both power sources are active at the same timeThe PD controller should provide a native orientation output to be used with an external 2:1 USB 3.1 Gen 1 (5Gbps) multiplexerThe board should only be powered if the attached USB-C source can provide a minimum of 45WI've been through the datasheets of perhaps a dozen USB-C PD options from all the usual suppliers. At this point I could really use some input or guidance from someone that's worked with USB-C PD before, as I've been struggling to align the above requirements with the myriad of PD controller options out there.Thanks!

author: jars121
author_rank: Regular Contributor
timestamp: December 20, 2020, 05:18:06 am
content: I had definitely planned on using an external mux for the data lines. The issue I've found with the PD controllers I've reviewed, is that you need to configure a GPIO on the PD controller to provide the orientation (e.g. CC1 is low, CC2 is high) line to the mux. I'd much prefer a dedicated output from the PD controller which provides this capability without having to program the PD NVM, or worse yet, control the PD registers via an external MCU at runtime. Ideally I could find a standalone option which doesn't rely on an external MCU interface. An optional MCU interface for monitoring the PD, checking the voltage and current level, etc. is fine, but I'm really trying to avoid requiring an external MCU and associated runtime process for managing source/sink and/or data role switching, advertising PDOs etc.