MCP73831 output reading issue / regulator heat

[kaning]

HI,
Im building a lipo charger with IC MCP73831 and im having some issues.

First one is after i mounted the circuit (5,1v supply) i got a output reading of 4,3v (i ordered 2ACI/OT,Vout=4,2v),on top says KD0W. is this value normal?? lipo betteries are very sensitive to overcharge so im afraid something goes wrong..

Second issue is about heat.
im using 16v solar panel, then step down converter with vout=10v to get more current into circuit. from here im using normal regulator with vout=5v to feed MCP73831 with is drawing 500mA. to simulate i was using laptop transformer with 19v 4,7A, the thing is regulator is heating a lot!! (im using heat sink) if im correct regulator is dissipating (10-5)*0.5=2,5W and it burns... and correct me if im wrong the current you get in the circuit is the current that circuit needs only right? so why its heating so much to regulate 5v?

many thanks

 

[crutschow]

What is the heatsink and did you mount the regulator to it with thermal grease? Are you sure the connections to the regulator are correct. Double check the pinout designations for the regulator package you are using.

 

[kaning]

Im totally sure about connections , im using the heatsink below only with isolation kit between regulator and heatsink for safety reasons.

https://www.ptrobotics.com/dissipadores/365-heatsink-to220-244c-w.html?search_query=dissipador&results=6

regulator is LM2941 it draws up to 1A

 

[chuckey]

That heat sink is 24.4 degs C per watt, you are dissipating 2.5w,so the heat sink will rise to 24.4 X 2.5 over the air temperature = 60 degrees C. If the air temperature is 20 degs C, then the heat sink will run at 80 degs C = VERY hot.
Frank

 

[kaning]

thanks for the reply frank,
last night i tried with another power supply this was 13v and 1,2A. Althought its less voltage it doesnt matter cause after step down it was again 10v and 500mA passing through regulator. so, calculations should be the same right? well the heatsink was just a bit warm, nothing compared as described above :s