-------------------------------------------------- From: "Sarin Sukumar A" Sent: Tuesday, August 03, 2010 7:09 AM To: "Microcontroller discussion list - Public." Subject: [EE]LM317 regulator output voltage fluctuation > I am converting 9V to 3.3V using LM317. > But here i met a strange problem. LM317 output fluctuates with a humming > noise. > my circuit has 3 another ICs working in this 3.3Voltage. But no one is > getting heated. > > do any one know any solution to this problem? > thanks for the help... > YOurs SaRIn.... > --=20 > http://www.piclist.com PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > Hard to say what's going on without more info really. A few questions.. Have you tried it with the LM317 output disconnected from the rest of the=20 circuit to help locate where the problem actually lies? Have you got the correct capacitance/loading on the LM317 as specified in=20 the datasheet? i.e is it within specifications for stable operation? What are the other ICs in the circuit? What is it's purpose? When you say fluctuates - how fast? Is it oscillating or just drifting? What pitch is the humming noise? Which part of the circuit does it seem to= =20 be coming from? =20 --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .