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LP8733: Short of VOUT_LDO0 & VOUT_LDO1

einfochips an Arrow Company
Intellectual 536 points
Part Number: LP8733
Other Parts Discussed in Thread: AM2432,

Tool/software:

Hi TI Team, 

We have a project where the VOUT_LDO0 and VOUT_LDO1 pins of the LP87334DRHDR are shorted together. Could you please confirm this configuration is acceptable or have any concerns regarding the same?

Thank you for your assistance.

Best regards,
Vaibhav Kundariya


  • 0
    TI__Genius 9907 points

    Hi Vaibhav, 

    This is not recommended. 

    Technically, both LDOs have the same output level and timing sequence, but they are not intended to be shorted together. 

    Since they are still operating independent of each other, I would strongly advise against this so that one output may not adversely effect the other. 

    What are the LDOs connected to?
    Are they powering multiple rails or a single output?
    Multiple rails can be divided among the two LDOS.
    Or if only one LDO is needed, then the other can be left floating.

    Best Regards, 
    Sarah

  • 0 in reply to Sarah Lao
    Intellectual 536 points

    Hi TI extert, 

    Thanks for your feedback. 

    Below is answer to your question. 

    Sarah Lao said:
    What are the LDOs connected to?

    LDOs will connected to AM2432 power rails. 

    Sarah Lao said:
    Are they powering multiple rails or a single output?
    Multiple rails can be divided among the two LDOS.

    It's powering multiple rails; however, having two separate power plans makes the layout complex.

    Could you please let us know what potential issues might arise if the outputs of two LDOs are shorted together?

    -

    Vaibhav Kundariya

  • 0 in reply to einfochips an Arrow Company
    TI__Genius 9907 points

    Hello Vaibhav, 

    Thank you for the context. 

    Primary concern would be the current draw.
    Current sharing between the two LDOs may not be equal if there is even any slight discrepancy in the output voltages.
    And as load current increases, one could reach overcurrent limit and cause voltage drop.

    This has not been tested on our end, so generally it is not recommended. 

    There is a general app notes on using ballast resistors to help balance load current
    https://www.ti.com/lit/wp/sbva100/sbva100.pdf

    But again, this has not been tested with the LP8733 LDOs specifically. 

    The design guide for LP87334D powering AM243x shows both LDOs having separate rails, this is the recommended connection:

    Best Regards, 
    Sarah