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TPS25750: Inquiry for startup behavior at power up

Part Number: TPS25750
Other Parts Discussed in Thread: TMUXHS4212,

Hello team,

My customer is considering to use TPS25750 for PD controller and TMUXHS4212 for  the flip of type-C USB super speed signal  as below. And the mode of TPS25750 is Power Source and power Sink as below.


In above situation, the customer has some questions.

Q1) The start condition of TPS25750 is power off. Then the customer wants to run TPS25750 in Sink mode to obtain 15V/3A when connected to a USB host through a Type-C cable. After that 3.3V (VIN_3V3) and 5V (PP5V) will be make From the 15V/3A obtained with DC-DC converters. 
After all system power is up and stable, the 15V power supply is switched to another power supply, and in some operating modes the TPS25750 is attempting to operate as source mode of  5V source from PP5V.
The Customer is thinking about this. Is it OK?   If there are any points to be careful, please give us advice.

Q2) The customer will be using the TMUXHS4212, but the customer is considering which is connecting TMUXHS4212 3.3 V power supply,  VIN_3V3 or LDO3.3V .would you please advise?

It's a complicated question, but I'd like to ask you some advice. Your help is appreciated.

Best Regards,
Akihisa Tamazaki

  • Hi Tamazaki-san,

    for Q1, there should not be an architectural issue with this. However, there is one thing to consider: When the TPS25750 boots from VBUS, it is booting in what's called "Dead Battery Mode". This means that the rail powering the TPS25750 is VBUS and there is no further power elsewhere in the system. There is no issue with doing this. However, when booting in this method, the TPS25750 would set the dead battery flag internally. When the dead battery flag is set, the TPS25750 would not be able to become a power source. So the customer would need to clear the dead battery flag before they attempt to source 5V in this case. They can do so by sending the "DBfg" command over I2C (explained in section 3.4.1 of the host interface technical reference manual: https://www.ti.com/lit/ug/slvuc05a/slvuc05a.pdf ). 

    For Q2, I would suggest powering the TMUXHS4212 over VIN_3V3 supply. The internal LDO on TPS25750 can only handle a few mA of current. We do not recommend using the LDO_3V3 for powering anything beyond the external I2C EEPROM.

    Thank you,
    Eric

  • Eric-san,

    Thank you very much for your clear answer. Your comment would be helpful for the customer.

    Best Regards,
    Akihisa Tamazaki