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LT3471 current

Looking at the datasheet the output current of the various designs seems to be linked to the Input Voltage. Is there a way to work out the current capability of a design?
I'm looking at producing a design that is:
12V in
+/-16V output at minimum 400mA per rail.
Is this possible?

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  • Yes, the output power increases as the input voltage rises, in Boost based applications.

    The dual app you're inquiring about uses a Boost and an inverting converters, with different capabilities. Additionally, there is more to just increasing the input level in order to get more output power, as internal dissipation becomes a limitation.

    Please post your max load currents. It’s better to start a design  with the max power desired, not the min. 
    Check out the LT8582. This part has >twice the capability and might be a better choice for you. 

    best,

    DV

  • HI,

    Sorry, that was a typo. 400mA maximum.

    Thanks,

    Graham

  • I see. Well, the capability in terms of switch current is close, but the inverter is pushing it over the guaranteed limit. 

    Also, the total power loss in the part itself could be a problem.

    I'd recommend you consider the part mentioned above, for your power level.

    Cheers!

    DV

  • Hi DV,

    Thanks, I'll take a look at that other part.

    How do you actually determine what is possible though, for future designs?

    Thanks,

    Graham

  • Hi, Graham,

    Here is a first approximation for a Boost converter, with a 3.3V input, 1A guaranteed switch current, and 12V out.

    This is just so you can get a first glance at load current capability, for a fixed switching frequency converter.

    Iout=(Vin*I*Eff)/Vout, or (3.3*1*.8)/12=0.22A.

    Where:

    Eff=converter efficiency, and I=guaranteed switch current.

    Also, a large inductor value is assumed, which is not always practical. 

    The inverter will have lower capability than the Boost, and requires a different approach.

    The LT8582 datasheet contains detailed procedures for the Boost and inverter converters on pages 13 and 15. Please read those for further details.

    Cheers!

    DV

Reply
  • Hi, Graham,

    Here is a first approximation for a Boost converter, with a 3.3V input, 1A guaranteed switch current, and 12V out.

    This is just so you can get a first glance at load current capability, for a fixed switching frequency converter.

    Iout=(Vin*I*Eff)/Vout, or (3.3*1*.8)/12=0.22A.

    Where:

    Eff=converter efficiency, and I=guaranteed switch current.

    Also, a large inductor value is assumed, which is not always practical. 

    The inverter will have lower capability than the Boost, and requires a different approach.

    The LT8582 datasheet contains detailed procedures for the Boost and inverter converters on pages 13 and 15. Please read those for further details.

    Cheers!

    DV

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