STUSB4700: Power Delivery Configuration Questions

[KMew]

Hello,

I am designing a USB-C Power Delivery circuit where our product is the source (NOT the sink). The system can be enabled/disabled via a user button, meaning the USB-C PD portion will lose its control supply power. I would like to be able to achieve either 60W or 100W charging capabilities and I would like the USB-C PD voltage/current settings to be remembered, even when power is lost (similar to a NVM).

I found one part that may be able to work for our needs (STUSB4700), but I am trying to understand how to design it currently. I have the following questions:

1) This is a general USB-C question. If the source is configured to do up to 100W (20V, 5A) but the sink is rated to less than that (Say, 15W/5V/3A, for example). As long as 15W is one of the configured power levels on the STUSB4700, does the communication between them both ensure it does not go beyond 15W?

2) The datasheet mentions "The STUSB4700 has a set of user-defined parameters that can be customized by NVM re-programming and/or by software through I2C interface." Since I want this to maintain the settings, even when supply power is lost, what is the simpler solution to do this?

3) To expand upon question 2, what do I need to program the settings I desire for the PD? For example, if I want 5V/3A, 9V/3A, 12V/3A, 20V/3A, 20V/5A, what hardware do I need to configure this? I see a reference to a STSW-STUSB002 GUI to configure it, but I am unclear on how to connect it to the STUSB4700.

Thank you in advance.

[Benoit FORET]

Hi KMew,

In order to make effective recommendations, may I ask 1st what is your application (AC/DC, DC/DC, single port or multi port) ?

The way USB PD negotiation works is the following:

1) the SOURCE shares its power profiles (advertising)

2) the SINK can request only 1 of the power profiles advertised

3) the SOURCE will accept (or not)) based on expressed SINK current requirement

4) SOURCE and SINK will transition to the agreed power node

5) SINK's duty is to draw no more current that the negotiated one (otherwise the SOURCE may collapse). The SINK (at application level) shall protect itself in general, and against unappropriate voltage (versus the negotiated one) especially.

6) The SOURCE (at application level) shall protect itself in general, and against overload/overcurrent especially.

Rgds,

Benoit

[KMew]

Hello Benoit,

Thank you for the reply.

Our application is a portable battery pack that can power a variety of different loads. So using a ~48V battery, we want to be capable of charging as many typical USB-C devices as possible (cell phones, battery banks, laptops, etc. There will be no data transmission and we do not wish to charge our internal battery via the USB-C. I hope that information helps you understand my application better.

Thank you very much for explaining how USB-C typically operates! This communication method will be very helpful when I begin working with it.

With this information, are you able to assist me with Question 2/3? Or do you require additional information?

[Benoit FORET]

Hi KMew,

OK. Clear. So let me recommend STUSB4710 instead of STUSB4700. STUSB4710 is cheaper and simpler to use.

You can download STSW-STUSB004 software package for the NVM customisation and follow the Quick Start instruction on the same web page. The related GUI is called: STSW-STUSB001.

Please note that this product is not able to check Cable current capabilities, so it can be configured up to 5A for captive cable implementation or 3A otherwise.

Rgds,

Benoit

[KMew]

Hello Benoit,

Thank you for the reply.

Our application is a portable battery pack that can power a variety of different loads. So using a ~48V battery, we want to be capable of charging as many typical USB-C devices as possible (cell phones, battery banks, laptops, etc. There will be no data transmission and we do not wish to charge our internal battery via the USB-C. I hope that information helps you understand my application better.

Thank you very much for explaining how USB-C typically operates! This communication method will be very helpful when I begin working with it.

With this information, are you able to assist me with Question 2/3? Or do you require additional information?