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LM20145 quiescent current with switching state

Atsushi Yamauchi
Genius 4810 points
Other Parts Discussed in Thread: LM20145, TPS54140

I would like to confirm the quiescent current of LM20145.

The customer wants to know it with switching operation. I understand it is difficult to define it.

If you have it, could you please teach it to me?

If there is not it, could you please teach the attitude for the quiescent current? If possible, could you provide the loss estimation (for example, datasheet page 39 of TPS54140)  of LM20145 to me?

Best regards,

Atsushi Yamauchi

  • 0
    Intellectual 500 points

    Hi. Atsushi Yamauchi!

    First attitude for the quiescent current: The Power supply part of device  is the interface to battery. there are norms about the maximum allowed current drawn by device if it not operating and the supply is not interrupted actively e.g. ecu connect to clamp 30 of car power supply system, it can have maximum 100 uA as quiescent current not to discharge the car battery if can is not used. Also for the devices at private house hold there some norms specially in European union.

    LM20145 is a controller with built-in switches therefor it is not easy to answer your question.

    if the switches are not built-in i.e. then you can define the current drawn by controller  if it is running, because the power flown to output has its own path and controller is drawing current to execute its task.

    In case of LM20145 there is single supply (controller + out going power) therefore you can do following.

    Pin = Pout/efficiency , you can just forget the current used by controller.

    Iin =Pin/Vin.

    I hope you can fallow it still it is toooooo late

    BR

    Bishnu

  • 0
    TI__Intellectual 1135 points

    LM20145 has PVIN pin(power stage input supply) and AVIN pin(Bias input supply to the chip), the input currents to both pins really depend on the application conditions when the converter is switching.

     If the customer wants to know the total input current into both PVIN and AVIN when the converter is switching with no load, you can use the excel calculator (http://www.ti.com/tool/lm20145design-calc) to calculate the efficiency and then based on the efficiency to calculate the power loss and then the total input current.

    The input current to AVIN pin consists of two parts, one is the  non-switching operating quiescent current available in the electrical table of the datasheet, and the other is the current corresponding to the gate drive loss which really depends on the VIN and fsw.