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LM5175: Power management forum

Tzachi Bear97
Intellectual 320 points
Part Number: LM5175

hi 

in my design i have incorporated the LM5715 as the main power after my battery/charger 

the 12v coming out of my LM5715 supplies all the other rails in the board

When i send the CPU to hibernate - most of the board power consumption goes down to low (<1mA) ,

but the buck boost consumes around 17mA, since we operate on a battery this is very high

is there a way to reduce the power consumption (or improve the efficiency) in low current consumption mode?

is this a problem - or just how the LM5715 operates in low current?

thanks

Tzachi

Scheme attached

IOWNT_PCBA200112_MOVE _ 05. STE.pdf

  • 0
    TI__Mastermind 21720 points

    Hi Tzachi

    Thanks for reaching out with your question and for considering the LM5175 in your design. 

    Based on the schematic it appears that the LM5175 is configured to operating CCM operating with  hiccup mode current limit protection. To help lower the IQ at lower currents the LM5175 can be configured to operate in DCM at light loading conditions. To implement this the MODE pin resistor can be changed to 49.9kOhm. 

    Please let me know if you have any questions.

    Thanks,

    Garrett 

  • 0 in reply to Garrett Roecker
    Intellectual 320 points

    Thanks Garrett,

    i will try this right away

    how much of a difference should this make?

    what is the trade off?

    Thanks

    Tzachi

  • 0 in reply to Garrett Roecker
    Intellectual 320 points

    Hi

    Changing the mode only gets me half way there

    in all other modes i can get as low as 8mA

    is there anything else we can do to improve this?

    thanks

    Tzachi

  • 0 in reply to Tzachi Bear97
    TI__Mastermind 21720 points

    Hi Tzachi,

    This is how the LM5175 operates in lower current mode in DCM. Note that when the UVLO pin is pulled high the LM5175 can sink 1.65mA on the VIN pin this is not including the current pulled by the gate driver, the feedback resistors or the UVLO resistors. Increasing the resistors on the FB and UVLO pin can help reduce the current levels. Also reducing the gate charge of the power MOSFETs and lowering the switching frequency will help reduce the gate drive current.

    Based off of the other designs, 8mA is pretty good.

    -Garrett