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Original question:

LM25141-Q1: Standby mode frequency

LM25141-Q1: Standby mode current

Wenyi Zhao1
Prodigy 255 points
Part Number: LM25141-Q1


Dear,

In LM25141-Q1 datasheet, it says it has a high-voltage bias regulator with automatic switch-over to an external bias to reduce the IQ current from VIN.

but in the page6,

the current when VCCX=5V is 42uA which is higher than 35uA when the VCCX is not attached to an external bias. why does it become higher?

Regards

Wenyi

  • 0
    TI__Guru* 76322 points

    Hi Wenyi,

    Note that the FB voltage is different in these two cases. When FB is tied to GND, the internal feedback resistor divider current is higher as the output is 5V. The main advantage of external VCC (VCCX) connection is that power is derived from a 5V supply and not the input voltage, hence a lower overall power dissipation.

    Regards,

    Tim 

  • 0 in reply to Timothy Hegarty
    TI__Prodigy 255 points

    Hi Wenyi,

    So, why isn't the power of 5V supply the power dissipation? I mean the current just transfers and still cause power consumption which may only lower because the VCC regulator doesn't work.

    Regards,

    Tim

  • 0 in reply to Wenyi Zhao1
    TI__Guru* 76322 points

    Yes, the power is lower as the current is derived from a lower voltage. This is the main advantage of connecting VCCX. Note that when the regulator is running in CCM, the controller must supply the gate drive current to the MOSFETs, which can be 10-30mA depending on the chosen FETs.