Quoting Brent Brown : > On 29 Oct 2010 at 0:04, David wrote: >> Schematic: http://tinyurl.com/2uhbr68 > > In the schematic T1 is a P channel MOSFET and it appears Drain/Source may= be > the wrong way around from what is intended. The symbol for the body =20 > diode gives it > away... with the orientation shown the diode will conduct and USB5V_SWITC= HED > will be on all the time regardless of the state of the Gate. Brent, thanks! Yes, this is backwards. What a stupid mistake on my part. > I'm not sure what C1 is there for. At power on, assuming C1 is =20 > discharged, it will try > to turn the MOSFET on - probably creating a a power on glitch in > USB5V_SWITCHED which may not be desireable. The datasheet appears to suggest that it forms part of the "soft =20 start" for the USB controlled power. Section 6.3 (page 25) of =20 http://tinyurl.com/32mwfp2 if you are interested. I'll fix that mistake. David --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .