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    LM2596 Issue (Burns out)

    Hello,
    I'm using LM2596 for the power supply of SIM800 GSM module.
    LM2596 is stepping down voltage to 3.8V. I have attached schematic diagram of it.

    It is working good if I use 12V-5A SMPS as power source. But when I use other supply like 24V-2A, LM2596 burns out while SIM800 is registering on network(during this time SIM800 draws more current). I'm not getting why it is burning out.

    •   Alt10th February 2018, 12:04

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    Re: LM2596 Issue (Burns out)

    As a first step check the schematic. D1 placed incorrectly. If this is the actual wiring, the switcher is likely to burn.

    Please also tell the inductor type.


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    Re: LM2596 Issue (Burns out)

    Quote Originally Posted by FvM View Post
    As a first step check the schematic. D1 placed incorrectly. If this is the actual wiring, the switcher is likely to burn.

    Please also tell the inductor type.
    Thanks for the reply.

    I have used this inductor : 68uH

    D1 should be placed before Inductor?



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    Re: LM2596 Issue (Burns out)

    D1 should be placed before Inductor?
    Yes, review LM2596 data sheet. Please notice that the inductor is only rated for 1.3 A continuous current. I guess it can work with GSM module.


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    •   Alt10th February 2018, 18:50

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    Re: LM2596 Issue (Burns out)

    Hello deep.kap,
    Try replacing R2 with a 3kΩ resistor as per datasheet calculations.
    What is the value of your input voltage?
    Regards,
    Relayer



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    Re: LM2596 Issue (Burns out)

    Try replacing R2 with a 3kΩ resistor as per datasheet calculations.
    Surely not. You apparently missed the 3.8V output voltage specification.



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    Re: LM2596 Issue (Burns out)

    When you multiply the Input Voltage, you multiply also the Power Dissipation on the IC, that's why it fails.( constant current is drawn by the circuit )



    •   Alt11th February 2018, 19:46

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    Re: LM2596 Issue (Burns out)

    Hello FvM,

    Surely not. You apparently missed the 3.8V output voltage specification.
    My bad. I didn't calculate it correctly. Thanks for pulling me up on that.

    Sorry about that deep.kap.
    Regards,
    Relayer



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    Re: LM2596 Issue (Burns out)

    @BigBoss, it is not a linear (series pass) device, so your comment may be a little wide of the mark.

    Without seeing the physical ckt it is hard to diagnose - the part is rated up to 40V in, if it is insufficiently heat-sunk then it may shut down due to over temp, as the switching losses go up with Vin...



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