Can anybody tell me the reason why L5973D will burn here?

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Esona
Posts: 3
Joined: Mon Apr 24, 2017 12:04 am

Can anybody tell me the reason why L5973D will burn here?

Post by Esona » Mon Apr 24, 2017 12:35 am

Hi, I want to ask for your help on my L5973D.

I used to use L5973D to produce voltage of 3.3V/4.2V according to the typical circuit in the datasheet. The figures are same while the feedback resistance are different. The input is 24V DC. They worked well without anything wrong.
L5973AD.JPG
(Test application circuit in the datasheet)

However, I met some problems when I want to produce 5V voltage according to the circuit above. I tried to turn the R1 into 10K. Theoretically,it will produce 5V, but when I connected it with 24V power,L5973D burned up. In the same circuit, the voltage is 3.3V when R1 is 5.6K. It worked well. I am wondering why...

So I’m here to ask for your help.Sorry for my poor English,but can anyone give me some suggestions?
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Olle P
Posts: 633
Joined: Tue Nov 04, 2008 6:03 am
Location: Sweden

Re: Can anybody tell me the reason why L5973D will burn here

Post by Olle P » Thu Apr 27, 2017 11:22 pm

I'm by no means well aquainted with this, and I can't fully understand how to figure out what the output is supposed to be given variations in R1 and R2.

The one possible issue that comes to mind is that if you just increase R1 to 10 kohm then maybe the total resistance of R1 and R2 is too high and V5 (feedback) gets messed up?

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