TUSB320: Is it necessary to have a bulk capacitor and a MOSFET when configuring DRP?

Additionally, it would be great if anyone could review the schematic I made for TUSB320 and let me know if it is ok or lacks anything, etc.

Thank you so much!

Jaein:

    Today is US holiday,  The assigned engineer will  response by tomorrow.

Best

Brian 

Hi Brian,

I hope you had a great Presidents' day.

I just wanted to follow up to this forum - thank you!

Best,

Jaein

Hi Jaein,

Jaein Cha said:

In this case, are the FET and the 150uF bulk capacitor (marked with yellow highlighter in the example schematic from the datasheet below) needed for the design? Or is it ok to connect VBUS to PMIC without the FET and the bulk capacitor to achieve a successful setup for DRP configuration?

Also, if the FET and the bulk capacitor are needed, could you let me know which type of FET should I choose? Should it be NMOS or PMOS? Are there any other parameters (operation voltage range, etc.) that I need to carefully pay attention to when choosing the FET?

I'm not fully sure if it is required or not, I believe I have seen systems that don't use this setup, but I will double check. It may also be good to check with the Power Delivery team over E2E, as I believe the BQ device is their part, so you may be able to get an answer from them.

Jaein Cha said:

Additionally, it would be great if anyone could review the schematic I made for TUSB320 and let me know if it is ok or lacks anything, etc.

Are you using I2C? If so, the SDA/SCL lines should be pulled up using a 4.7KOhm resistor to 1.8/3.3V,

Please ensure the ID pin is communicating with the host or with a VBUS switch. When the ID pin is low, this indicates that the device is configured in DFP mode, and should be supplying VBUS. If the ID pin is not set correctly, it will cause issues when being used in a DFP application.

Otherwise, I don't believe I see any other issues with this schematic. Again, I will double check on the FET requirement.

Thanks,

Ryan

Hello Ryan,

Thank you for the reply.

Ryan Kitto said:

Are you using I2C? If so, the SDA/SCL lines should be pulled up using a 4.7KOhm resistor to 1.8/3.3V,

For this, the I2C bus is connected to MSPM0G3507 (MCU), and the lines are pulled up with 4.7KOhm resistors to 3.3V on the MCU's schematic.

I excluded pullup resistors in this schematic as, to my knowledge, the entire I2C bus needs only one pair of 4.7kOhm pullup resistors (one for each line for the whole I2C connection). Could you let me know whether it is correct?

Ryan Kitto said:

Please ensure the ID pin is communicating with the host or with a VBUS switch. When the ID pin is low, this indicates that the device is configured in DFP mode, and should be supplying VBUS. If the ID pin is not set correctly, it will cause issues when being used in a DFP application.

Regarding this, both the ID pin and INT# pin are connected to the GPIO pins of the MCU. Does the host mean the MCU? In the system I'm working on, the MCU will be the subsystem responsible for integrating/controlling other subsystems into one working system. Should it work without issues when those pins are connected to the MCU GPIOs?

I appreciate your detailed response. I'll also reach out to the Power Delivery team regarding the correct setup when used with a BQ device.

Thank you, and I look forward to hearing from you regarding the FET requirements!

Best,

Jaein

Hi Ryan,

Thank you so much for your help!

I have one last question.

For the FET, can I use any type of FET? For example, just a N type MOSFET from any manufacturer with any operation range (or viltage range, etc.) would work? Or is there any specific parameter/specification that I need to check to choose a FET for successful implementation?

I feel like this might be also a trivial question but I appreciate your help a lot.

Thank you!

Best,

Jaein

Hi Jaein,

I believe an N type MOSFET would work, so long as the gate voltage threshold can be passed with the GPIO from your MCU. I don't have any recommendations as for which FET to use though, sorry about that.

Thanks,

Ryan

Hi Ryan,

Thanks a lot for the help.

I used an N type MOSFET with Vth of 0.85 V (min) −1.5 V (max), which my GPIO's high voltage (3.3V) would exceed, to update my implementation.

The attached image below is my final schematic.

Thank you again,

Jaein

Hi Jaein,

Just to confirm, VBUS is still being controlled by the VBUS switch, correct? The drain just connects to the VBUS output from the switch?

Otherwise, I don't think I have any other comments.

Thanks,

Ryan

Hi Ryan,

If I'm not wrong, I think the VBUS is also going to be connected to a power mux (TMUX1248DCKR) designed by TI.

Is that considered a type of VBUS switch?

I think it will be connected like the diagram below - the VBUS will be connected to the drain and the VOUT of the switch, but I will double check with the teammate who is designing a board for TMUX.

Thank you!

Best,

Jaein

Hi Jaein,

As long as it can control VBUS (which it looks like it can) and can be controlled via the GPIO of the MCU, then I think it should be okay. Looking at the mux you have picked out, it does say the max signal it can mux is up to VDD, so make sure VDD is at least 5V. Otherwise, as long as the implementation is similar to what is on the datasheet typical application, I don't have any issues.

Thanks,

Ryan

Hi Ryan,

Thank you so much for all the help and comments!

That sounds great, and yes, I will make sure the VDD stays above 5V.

It was so helpful for me to understand the TUSB-based system better.

I appreciate your help.

Best,

Jaein