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TPS61175 + high side switch

Other Parts Discussed in Thread: TPS61175, TPS1H100-Q1, LM3880


I am working on a circuit that has a +24 V switchable output (max. 1 A). The input voltage of +12 V is first boosted to 24 V using the TPS61175. Because I do not want +12 V at the output when the boost converter is off; I include the TPS1H100-Q1 high side switch to control the output. I do not know how well the TPS61175 behaves at zero load (TPS1H100-Q1 disabled). I am aware of the TPS61175 errata that recommends >60kohm at its frequency pin.

What would you recommend?

(A) Just have the boost converter always on, switch the output using the TPS1H100

(B) Connect the EN pins of the boost converter and the high side switch together; both will startup at the same time

(C) Use a sequencer IC (e.g. LM3880) to make sure that on startup the boost converter is first on, and on shutdown last off.

  • Hi Andrew,

    For the TPS61175, when its operation frequency is lower than 1.2MHz, it can enter into the skip mode at the no load condition. So you needn't add the dummy load at the output side when Fsw<1.2MHz. So
    1) if fsw<1.2MHz, then you can have TPS61175 laways on(the output capacitor should be connected at the output of TPS61175 instead of after the TPS1H100), just switch the TPS1H100;
    2)  if fsw is >1.2MHz, you can control the boost and the high side switch at the same time use the EN signal. But you need to take the start-up time of the boost converter into account.

    What is the boost converter's minimum operation duration, will it be enabled and disabled frequently?

  • Use a sequence IC is too complex in this kind of application.