Christopher Head wrote:
> That said... anyone up for making a tiny circuit (I'm thinking, around
> the size of a flash stick) that plugs into a USB port and has a little
> tiny switching boost regular, plus maybe a linear, and brings whatever
> you have on the port up to a perfect 5V? Then you'd just plug a
> regular USB cable into the other side of the circuit. You could
> market it at EEs as a way to stabilize voltage so you can use cheap
> programmers like the PK2

Or you could get a USBProg which has this built in.  See page 1 of the
schematic at http://www.embedinc.com/products/usbprog/eusb3.pdf.  The PIC
10F204 (IC2) controls a boost switcher that makes about 8.2V.  After a
diode, this is linearly regulated to a steady and clean 5V by IC1.  The 8.2V
is the power input to the programmable target chip Vdd linear regulator on
page 4.  These two circuits allow the USBProg to work with any legal USB
voltage but to still guarantee up to 6V target Vdd at 100mA.

This is part of the extra robustness I was talking about that a "production"
or "professional" programmer needs versus a hobby or development programmer
like the PicKit2.  Of course this is one reason the USBProg also costs more.
For hobbyist the $35 PicKit2 is a great deal.  For professional or
production use the extra $45 for a USBProg is cheap compared to even a
single field failure or having to figure out why it's not working this time.


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