Thermal Junction Temperature. What is your input voltage, output voltage, and desired current output? What is your current available on input?Only the LM2596 which provides 5V output is blowing up not the other one, Why ?
Here's the schematic and layout for your reference
View attachment 248932
View attachment 248933
Thank you much in advance
What about D4?Did you check D4?
Thank you for your comment, My input voltage is between 12 to 13.5 V, I have two output voltages one dc-dc each, 5V and 8V, the 5V one is blowing up on reverse polarity. Desired current is 250mA to 500-600mA.Thermal Junction Temperature. What is your input voltage, output voltage, and desired current output? What is your current available on input?
Thank you for your comment, i took 470uH from the dc-dc module i have used and seen many times, i have never seen an LM2596 module with the recommended value as per the datasheet, so i went with the one i have used and actually seen.How did you arrive at 470uH inductors? These appear to be much larger then the chip manufacturer's recommended value range. And what spec are your diodes and output capacitors?
Thank you for your comment, My Vin is approx. 12V never below 12V and never above 147V, nothing has been purchased from Aliexpress, everything came in assembled from JLCPCB but in my design i had added an SOD-123FL diode (SM4007PL) but the diode was heating up way too much instantly causing the IC to heat up as well, so i de-soldered it and replaced it with SS34 (package - SMA-DO-214AC) from an LM2596 DC-DC module, it worked perfecty without any heating issues at all. So i ordered some SK34A (package - SMA-DO-214AC) from RS Components since i couldn't find SS34.likely one of 2/3 reasons, Vin too high, too much soldering is killing it, you bought the parts from Ali-express,
Could be all 3.
Sorry not 147V just 14VThank you for your comment, My Vin is approx. 12V never below 12V and never above 147V, nothing has been purchased from Aliexpress, everything came in assembled from JLCPCB but in my design i had added an SOD-123FL diode (SM4007PL) but the diode was heating up way too much instantly causing the IC to heat up as well, so i de-soldered it and replaced it with SS34 (package - SMA-DO-214AC) from an LM2596 DC-DC module, it worked perfecty without any heating issues at all. So i ordered some SK34A (package - SMA-DO-214AC) from RS Components since i couldn't find SS34.
You're right about the 470uH i got mistaken by the printed 470 on the inductor i guess, because even for 47uH it still says 470 -_-The 470uH is much too large. For 12v to 5v at 250 - 800mA, 47uH would be better. The higher inductance is generating large voltage spikes and forcing the switching speed down which is stressing the chip, despite its internal overheat limiting. I think it only luck the 8v regulator hasn't died yet. Do you actually know the current draw when failure occurs?
As you already know, the original diodes were completely wrong for this purpose. The new ones are better...
Your PCB tracks to the chip are on the thin side. What's on the back side of the PCB? There's probably not enough heatsinking.
Do you have a link to the output capacitor datasheets? Or the specific parts you purchased?
Thank you for your comment i really appreciate it, I think i am using a fake LM2596. Guessing because it's not from Texas Instruments.Hello,
Did you have a look at the pages 19 and 20 for inductor selection?
There is no 470 μH in those tables.
Bertus
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