I added capacitors on input and output but the voltage is stopping and output is not stable.How should I correct it?
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I added capacitors on input and output but the voltage is stopping and output is not stable.How should I correct it?
Hi Riya,
Any Linear Voltage Regulator dissipates power as a function of (VIN-VOUT)*ILOAD. So if your output is 10V:
(12-10)*0.3=600mW of power dissipation. For the SOT-223 package:
The thermal rise on the die would be RthetaJA which is 59.3C/W times the power dissipation of 600mW plus the ambient temperature:
TJ = TA+Power Dissipated*RthetaJA or
TJ= 25+0.6*59.3=60.6 which would be fine.
However, if VOUT is 5V, then this changes:
The power dissipation is (12-5)*0.3 or 2.1W.
So TJ=25+2.1*59.3=149.5C which is going to trigger thermal shutdown.
Note: I used TA as 25C but actually in the application this should be the PCB ambient which could be higher. Changing to the TO-220 package would help a lot.
I hope this helps.
Hi Riya,
The device is electrically capable of supporting 1A, but thermally it depends on the voltage drop across the device and the current as described above.
For VIN=25V and VOUT=12V at 300mA, this is 3.9W. 12V to 7V at 300mA is 1.5W of power dissipation.
I think you are running into thermal shutdown.
Does this help?