ADP2360 as dc-dc converter for loop-powered system

Hi 

I'm designing a board which will be powered from loop-powered system with  24v/3.2mA input.

I want to convert it to 3.3V/12mA output.

So i want to use adp2360 as dc-dc converter but the problem is in LTSpice the minimum input current from supply is 50mA , which can be maximized with Rith.

I want to know if these type of dc-dc converter can be use for loop-powered application , and if not , is there any suggestion?

Thanks

Best Regard

Parents
  • +1
    •  Analog Employees 
    on Oct 1, 2018 7:01 AM

    Hi David,

    The ADP2360 should be able to supply the 3.3V/12mA from loop powered system with 3.2mA input current and 24V supply provided that the you allow the input capacitor to charge up (from the 3.2mA current, 24V supply) before turning ON the ADP2360 or the 12mA load because the input capacitor will supply the 50mA pulse currents during normal operation.

    You can add resistor dividers (from VIN to EN then EN to GND) to make sure that the ADP2360 will be enabled only when the VIN is >16V to make sure that it will turn ON.

    POUT = 3.3V*12mA = ~40mW, PIN @ 80% efficiency = 50mW, IIN (max) = 3.2mA, VIN(min) = 15.6V

    I think, what you are seeing in the simulation is that the part is going into hiccup mode:

    1. The ADP2360 starts switching when VIN is higher than the UVLO threshold 4.4V.
    2. Because the load is ON and the input capacitor hasn't been charged up, the VIN drops below UVLO falling threshold 4.2V.
    3. Then the part stops switching allowing the input capacitor to charge up again.
    4. then go back to #1 when the VIN crosses the UVLO rising threshold
    5. then repeat.
    6. Can you confirm that this is the case.

    You might want to look at the LTC3642 as the current limit can go down to 25mA.

    Thanks and regards,

    Jefferson

Reply
  • +1
    •  Analog Employees 
    on Oct 1, 2018 7:01 AM

    Hi David,

    The ADP2360 should be able to supply the 3.3V/12mA from loop powered system with 3.2mA input current and 24V supply provided that the you allow the input capacitor to charge up (from the 3.2mA current, 24V supply) before turning ON the ADP2360 or the 12mA load because the input capacitor will supply the 50mA pulse currents during normal operation.

    You can add resistor dividers (from VIN to EN then EN to GND) to make sure that the ADP2360 will be enabled only when the VIN is >16V to make sure that it will turn ON.

    POUT = 3.3V*12mA = ~40mW, PIN @ 80% efficiency = 50mW, IIN (max) = 3.2mA, VIN(min) = 15.6V

    I think, what you are seeing in the simulation is that the part is going into hiccup mode:

    1. The ADP2360 starts switching when VIN is higher than the UVLO threshold 4.4V.
    2. Because the load is ON and the input capacitor hasn't been charged up, the VIN drops below UVLO falling threshold 4.2V.
    3. Then the part stops switching allowing the input capacitor to charge up again.
    4. then go back to #1 when the VIN crosses the UVLO rising threshold
    5. then repeat.
    6. Can you confirm that this is the case.

    You might want to look at the LTC3642 as the current limit can go down to 25mA.

    Thanks and regards,

    Jefferson

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