Hi all, This is my first post, so please bear with me if I've done anything wrong. I've tried search the forum and have had no luck. I'm using a Traco-Power TMLM04 switch mode power supply to power a very basic circuit with a PIC16F722. I've been having real problems with the PIC resetting it self due to brown-outs. I scoped the 3.3V DC power line (the output from the TMLM04 module) and it was very very noisy. The data sheet for the TMLM04 module states that with a constant load, the maximum output ripple should be 250mV. To check that the error wasn't in the circuit I had made, I connected the module to a very basic circuit with just a 15Ohm load resistor. This gives a constant load of ~220mA (max output is 1200mA), and I scoped the output again. The noise from the power supply module is just as bad as with the original circuit and I'm seeing ripple of up to 2.5V at the worst points. I have about 50 of the Traco Power modules, of which I've tested about 10 in total which span 3 different batches and they're all the same. So I'm sure it must be something I'm doing wrong. I've tried adding a 2200uF capacitor on the 3v3 line, which helps a little, but not much. Here is a screen shot from the 3v3 line of the basic (15 ohm resistor only) circuit. The centre line is 0v, the volts per division is 1V and the time per division is 5mS. There is a copy of the data sheet and extra information available from here: http://www.tracopower.com/products/ac-dc-power-supplies/encapsulated-modules/ Any help with how to reduce the noise to make it suitable for use with a uController would be much appreciated.