ADP2360 as dc-dc converter for loop-powered system

hi, i also have this problem. i tested the circuit and saw the problem, the loop power systems must have the maximum current of 3.2 ma in 24v system but in this ic , the input current on 24v in best situation is 50ma peaks and i think there must be some problem in adp2360 input circuit.(because of iswitch).i have also this same question.best regards

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

Dear jefferson i test the thing you said in ltspice as the attached file but the input current is 50ma peak yetadp2360.rar

Hi Azita,

I think it is because there is no current limiting on the power supply. You can add an ideal diode and set the current limit to 3.2mA. I attached here the circuit I've used and the part works okay.

Thanks and regards,

Jefferson

ADP2360-3.3_Voltage Supply_Current_Clamp.zip

Dear jefferson thats right thanks for that it is now solved.