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Original question:

BQ25121: Excess quiescent current draw beyond specification when enabling the LDO in some devices

BQ25121: LS mode current capability?

Divya Jyoti Pandey
Prodigy 20 points
Part Number: BQ25121

Tool/software:

Could you please provide the capability specifications for the BQ25121 in Load Switch (LS) mode? The datasheet details the LDO mode extensively, but the LS mode's current capability is not mentioned explicitly.

Thank you for your assistance!

  • 0
    TI__Genius 13705 points

    Hi,

    The LS current capability is dependent on your input voltage and voltage tolerance. Something like a 10% tolerance with a 4V input would mean that your LS should be able to provide around 350 mA, but with a 5% tolerance this is limited to about 180 mA.

    Best Regards,

    Juan Ospina

  • 0 in reply to Juan Ospina
    Prodigy 20 points

    Hi Juan,

    Thank you for your response.

    I appreciate the details regarding the LS's current capability, which depends on the input voltage and voltage tolerance. However, I need to confirm the exact current capability of the Load Switch (LS) mode for the BQ25121 IC, considering the internal MOSFET(Q5) that manages the VINLS and LS/LDO output. 

  • 0 in reply to Divya Jyoti Pandey
    TI__Genius 13705 points

    Hi Divya,

    Just to clarify you want the maximum current that the device is able to provide, regardless of if output voltage drops to 0?

    Best Regards,

    Juan Ospina

  • 0 in reply to Juan Ospina
    Prodigy 20 points

    Hi Juan,

    I appreciate your support.

    Please refer to the datasheet of BQ25121A(page - 28). I found two points in the datasheet:
    1. If a value greater than 3.3 V is written, the setting goes to a pass-through mode where LS/LDO = VINLS - V(DROPOUT).
    2. The current capability of the LDO depends on the VINLS input voltage and the programmed output voltage.

    The datasheet discusses only LDO mode and does not provide information about LS mode. However, I assume LS mode also works in a pass-through mode where LS/LDO = VINLS—V(DROPOUT). 
    Now, I want to know the maximum current that Q5 can handle (please refer to the 9.2 Functional Block Diagram in the datasheet) in this mode.

  • 0 in reply to Divya Jyoti Pandey
    TI__Guru** 103185 points

    Hello Divya,

    Our responses will be delayed due to the U.S. holidays, we will respond by the end of the week.

    Sincerely,

    Wyatt Keller

  • 0 in reply to Divya Jyoti Pandey
    TI__Genius 13705 points

    Hi Divya,

    The absolute Max LS/LDO current we provide is 150mA.

    Best Regards,

    Juan Ospina