On 6/9/05, Olin Lathrop wrote: > Rodrigo Real wrote: > > I've been working for some time using the 78XX series as regulators, > > but I was never very satisfied, specially because of the heat > > generation and poor quality of the regulated voltage. > > > > I am now testing the LM2575/76 series, which seems to performance > > better. It is switched and uses an internal frequency of 50KHz, we can > > see in the output voltage some spikes (the ouput voltage varies in > > +-10%) in this frequency. I reduced the spikes using an > > inductor/capacitor filter, but I could never eliminate it when I > > have load. > > > > So, my question is, considering that I will power a PIC and some other > > circuits (mostly discrete) should I be worried with those spikes? > > Probably not. Unless you've got a truly horrible circuit, the PIC Vdd > should still stay within the min/max limits for your PIC and oscillator > frequency. While the PIC will probably run fine, spikes can cause serious > trouble to analog circuitry. If everything is digital and you're > guaranteed > always within 4.75 to 5.25V than you'll be fine. > > Lately I've been using a 5.5V switcher followed by an LDO to make clean > 5.0V. The Microchip MCP1700 is a nice LDO for that purpose. It can > deliver > 1/4 A if I remember right, and with only 1/2 V drop you can use the tiny > SOT-23 package without running into heat problems. The output of the > MCP1700 is very clean. Hi Olin, How clean compared with the switcher output (I'm interested only about the switching ripple component and LDO output ripple using a pure resistive load, if you measured) ? thx, Vasile > > > ***************************************************************** > Embed Inc, embedded system specialists in Littleton Massachusetts > (978) 742-9014, http://www.embedinc.com > -- > http://www.piclist.com PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist