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TPS5430: Dc dc buck converter no load current

Mayank Gupta2
Prodigy 160 points
Part Number: TPS5430
Other Parts Discussed in Thread: LMR33630,Hi, We have been using TPS54302 in our designs and it works like a charm. We used the same device in one of upcoming project which involved the system to be solar powered with 12V SMF battery. The overall sleep current for full system should be 10mA at 12V for prolonged battery life. We designed the system with TPS54302 and the load testing passed for full load conditions. But we observed that even at no load TPS54302 is consuming 10ma at 12 V input and 5V output. Clearly this will not meet our sleep current requirements because MCU and some other low poer electronics will also be enabled during sleep mode. It is not clear why such high consumption at no/low load. Also suggest alternate part for same.
  • 0
    TI__Guru 57555 points

    Hello

    This is a rather older, non-synchronous device, and as such it does 

    not have a "light-load" mode.  Most of our newer devices will reduce the 

    switching frequency with light or no-load; to lower the input current and improve the efficiency.

    Please look at the LMR33630 family of devices.

    They are offered in the same package and will have 

    a no-load input current of about 25uA (see data sheet).

    Also, see application note SLYY189.

    Thanks

  • 0 in reply to Frank De Stasi
    Prodigy 160 points
    Hi Frank, Thanks for quick reply. The part we are using is TPS54308, is synchronous fixed frequency converter in sot6 package. The datasheet says Iq (non switching) is 300uA. But practically i think device is always switching and goes in fccm mode at low load. The observed current at input was 10mA which was many times higher then Iq value What is the best way to read datasheet to understand low load current of dcdc buck converters? I will have a look at LMR33630.
  • 0 in reply to Mayank Gupta2
    TI__Guru 57555 points

    Hello

    The best way to tell is to look at the data sheet.  If it does not state a light load mode or the input current at light load,

    then you can expect it will be somewhat high.  The non-switching Iq is not a good indication.  Please see SLYY189 for

    details.

    Thanks

  • 0 in reply to Frank De Stasi
    Prodigy 160 points

    Thanks for your application note. Now i have a better understanding while reading datasheets.

    Also, replaced TPS54308 which TPS54302 which has 70% efficiency at light load conditions or 1mA as per datasheet.

    Results: 12V in, 5V out, No load

    Input Current is 0.08mA

    Results: 12V in, 5V out, 10mA output load.

    Input Current is 4.7mA