• State Resolved
  • Locked Locked
  • Replies 4 replies
  • Subscribers 34 subscribers
  • Views 296 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

TPS65988DJ: Using VIN 3V3 instead of LDO output

Mehmet Alper USLU1
Prodigy 40 points
Part Number: TPS65988DJ
Other Parts Discussed in Thread: TPS65988

Hi,

It is shown in the datasheet of TPS65988, LDO 3V3 output is connected to VIN 3V3 by a single directional switch. All SPI and I2C lines are pulled up with LDO 3V3 output which should be the same when VIN 3V3 present. We have dedicated 3V3 system power and can I directly connect SPI and I2C pull ups 3V3 rather than LDO 3V3 output? Is there any side effect of connecting SPI and I2C pull ups directly to 3V3 rather than LDO 3V3 output?

Finally, it is recommended to connect I2C2 lines to pull-up resistors even we don't use them. Could you please let me know what is the adverse effect can be seen if I2C2 lines are not connected to pull-up resistors?

Many Thanks & Regards;

Mehmet

  • 0
    TI__Expert 8750 points

    Hello Mehmet, 

    LDO 3V3  domain will be available whenever PD controller is powered and pulling up interface (I2C/SPI) lines to this domain ensures that the pull ups are active whenever PD controller communicates. You can pull interface lines to VIN 3V3 if you can meet this requirement. 

    "Finally, it is recommended to connect I2C2 lines to pull-up resistors even we don't use them. Could you please let me know what is the adverse effect can be seen if I2C2 lines are not connected to pull-up resistors?" Floating I2C lines may cause small additional power consumption, I don't see any other adverse effect. 

    Thanks

    Prajith

  • 0 in reply to Prajith Cheerakkoda
    Prodigy 40 points

    Thanks a lot Prajith, as a final question, I saw that external path enable pins are connected to both external path transistor and enable pin of power converters in EVM schematic in order to cut the source power when sink mode is activated. Do we have to cut source power by using the same approach when sink mode is enabled? Can the source power be remained as 5V default during sink mode (source power path is internal, sink power path is external)?

    Many Thanks & Regards,

    Mehmet

  • 0 in reply to Mehmet Alper USLU1
    TI__Expert 8750 points

    Hello Mehmet,

    Internal power path has inbuilt OCP protection so we use the internal power path for Source (As per spec OCP protection is required for Source) and external path for Sink. 

    PP3/4 GPIOs are to control external power path transistors and there are GPIOs for controlling DCDC feedback to set desired source voltage. PD FW will take care of disabling internal path when transitioning to Sink mode. In addition, RCP (reverse current protection) will protect Source DCDC from higher voltage from far-end.

    "Can the source power be remained as 5V default during sink mode (source power path is internal, sink power path is external)?"

    Yes, PD controller will shut down the Source path when transitioning to Sink mode. 

    Thanks

    Prajith

  • 0 in reply to Prajith Cheerakkoda
    Prodigy 40 points

    Thank you very very much Prajith!.

    Kind Regards,

    Mehmet