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Questions about using FUSB301 in Inn3378c design

Posted by: jason brody on Tue, 06/01/2021

Hi. I`m the student developer who is frequently using your product.

While Using Pi Expert Online, Part MCU raise my curiosity. If MCU is not specified, than I can use any microcontroller including USB HUB?

The schematics your company provide uses vp302 but no VP302 datasheet is found in the internet, so I use FUSB301 to finish the work. But I have wonder.

Can I use any MCU including FUSB301, FUSB302 (provided by on semiconductor) or USB7050(USB-C hub Controller by Microchip) in Innoswitch 3 schematics?

I`m using L6562 PFC controller to provide 400VDC in my Innoswitch.


Submitted by PI-Sky on Tue, 06/01/2021

Hi Jason,

Yes you can use FUSB301, 302, and USB7050 but you will need an actual MCU (ex. PIC/STM). FUSB301 and 302 are Type-C controllers and have no way to control the actual InnoSwitch IC. Interfacing an MCU will allow it to process the information from these controllers and then communicate with the InnoSwitch IC. You also need the firmware for these IC's and integrate the InnoSwitch library to it.


As for the USB7050, this is a hub controller and quite overkill if you're not going to implement multi-output along with alternate modes such as HDMI support.

I suggest you use UPD301a if you're going to implement usbpd.




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Submitted by jason brody on Sun, 06/06/2021


Than what you`re saying is, Using MT7628 or MT7621(Router CPU) or USB7050 as an MCU won`t work . Is that correct?

I must bypass the USBPD signal using 32bit ARM MCUs?(I wish I could use atmega 8 bit-MCU series like Atmega328p though)

And I`m Wondering about Using Earth Protection to my schematics, too. The Pi Expert solution only provides P,N or HIGH DC Positive and Ground.

(I`m using Kicad tool, and Earth mark is directly connected to Earth Protection Line.)

Submitted by PI-Sky on Tue, 06/08/2021

USB7050 can be used as a MCU, but it is a bit overkill based on your design.

You can actually use Atmega328p as we've also used it before. As for the MT7628, looking at the datasheet suggests that it can be used. The only real requirement for an MCU is that it has a 3.3V I2C I/O so MT7628 seems fine.

There's no option to directly add an Earth ground to the PI Expert design but you can add it when you're creating your schematic.

I`m currently working on Two projects. One is using MT7628 and Arduino 328p, and FUSB301. That worked out well thanks to your advice.

The problem happened in other project that uses USB7050 (I literally hooked up 3 inn3378 into my project so that I can hook up 3 powerful device into my project).

It seems that inn3378 can produce only one i2c slave address '0x18'. In my knowledge, same slave address is not tolerated in I2c. So I use I2C multiplexer to solve this problem.

Is this the right solution? Or did I miss something in Datasheet?

Submitted by PI-Sky on Wed, 07/14/2021

Hi Jason,

You're right. We also use a multiplexer for this application