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[SOLVED] LM2596 Issue (Burns out)

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deep.kap

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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.
 

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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.
 
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?
 

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

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

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 )
 

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. :wink:

Sorry about that deep.kap. :oops:
Regards,
Relayer
 

@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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