I am using LP3982 to generate 3.3V. Initially when the board was assembled the voltage is proper at 3.3V. After keeping the board ON continuously for 2 to 3 hours the voltage is either 0v or 0.72V. Similar is the case for LP3982 to generate 1.8V. Initially I am getting 1.8V and after some time it changes to 0.7V. Please advise
HI Kamala Kris,
To properly advise you on what might be happening, can you share which package you are using and the input voltage and load current for your application? Also when the voltage is 0V or 0.72V is this being measured with a multi-meter or with an oscilloscope?
The reason I am asking is that I am wondering if the part is going into thermal shutdown. For example, if you are using the VSSOP package the Tja is 175.2C/W as shown below:
For example if your VIN is 5V and the load current is 200mA, then for 3.3VOUT this is 1.7x0.2A or 340mW of power dissipation. So with a proper layout (i.e. HIgh-K Board), the device junction temperature would rise to 0.34W*175.2C/W or ~59.6 above the PCB ambient. In your application you can use the RThetaJC(TOP) to measure the actual junction temperature. To do this, you would need to glue a thermal couple to the top of the device to see how hot it is getting in your application. Then by knowing the actual power dissipation in the device, you can calculate how much hotter the devices junction is than the top of the package.
If you can share more details, on your application, I can better help to to resolve this quickly.
I hope the above information is helpful.
