Power from USB & DC Adapter (was Re: Design Files/Gerbers of SAKC V2)

Carlos Camargo cicamargoba at gmail.com
Fri Jul 30 11:35:39 EDT 2010


For the +/- protection, some designers put a diode between the main power
and the regulators, this is the cheaper but not elegant option.
I've already have one option for +5V collide protection.

The power supply is a sensible topic in the design, we can't provide a wide
range of voltages, with a high current capacity. If you need an application
with special voltage you must provide this voltage, SAKC is just the brain.
Arduino for example, works with 5V, and have one 5V LDO, this LDO is not
good for battery applications like robotics, because don't works under 5V,
the better choice is a switching power supply, but again is for an specific
application.

I think that the daughter card will have the specific power supply, so we
can reduce the SAKC complexity and maintain the flexibility.



Carlos




On Fri, Jul 30, 2010 at 10:17 AM, David Reyes Samblas Martinez <
david at tuxbrain.com> wrote:

> I must agree with Ron that we don't have to save in "poka yokes" on
> the power sourcing on SACK
> +1 to the  +/- protection
> +1 to the +5V collide protection
>
> and how much cost and space is for the power regulator?
>
> 2010/7/30 Ron K. Jeffries <rjeffries at gmail.com>:
> > Please make sure that the design protects
> > against plus and minus being plugged in wrong.
> > I think that implies a zener diode.
> > the extra cost of a 5V supply that accepts a fairly
> > wide range of input voltage say 12v or less
> > is probably worth it IMO
> > SAKC is prolly less price sensitive than Nanonote.
> > ---
> > Ron K. Jeffries
> > http://ronkjeffries.posterous.com
> >
> >
> >
> >
> >
> >
> >
> >
> > On Fri, Jul 30, 2010 at 07:44, Carlos Camargo <cicamargoba at gmail.com>
> wrote:
> >>
> >> Hi Adam
> >>
> >>
> >>
> >> On Fri, Jul 30, 2010 at 8:53 AM, Adam Wang <adam at sharism.cc> wrote:
> >>>
> >>> Hi,
> >>>
> >>> 1, I made a mistake on D10 footprint confirmation, It must be 0805 to
> >>> meet MSCD104H. Pls change this to 0805 package.
> >>
> >> ok, I'll fix it
> >>
> >>
> >>>
> >>> 2, maybe mark a concentric circles with central ring to mark "+" and
> >>> outer ring marked a "-" nearby DC Jack to suffer from mistakes by
> novices.
> >>
> >> Agree
> >>
> >>>
> >>> 3, last but not least, current design of SAKC V2 have a condition that
> is
> >>> it can not use +5V power at the same time either from USB cable
> (0.5A) or DC
> >>> adapter(can be more). If using DC adapter fixed +5V in already,
> >>> you must _remember_ to take out mini-jumper on J18 first, then plug-in
> usb
> >>> cable to do s/w work. If you forgot that take out mini-jumper, after
> >>> plugging usb cable; There must be have power +5V "collide" together.
> This
> >>> UNSAFE condition will be happened once mindless to forget to take out
> >>> mini-jumper. And possibly let USB host device to be have damage or even
> DC
> >>> adapter source. Also if remove DC adapter, the SAKC it can only get
> 0.5A
> >>> from usb, unworthy a bit. so
> >>>
> >>> 1) remove the DC adapter reducing the hardware hacking usability of the
> >>> board a lot.
> >>
> >>
> >>>
> >>> 2) remove USB power, adding the need for an extra power adapter for
> every
> >>> user.
> >>
> >>
> >>>
> >>> 3) add additional circuitry to make both USB & DC power stable in all
> >>> cases. User should have the chance to update s/w from USB while still
> some
> >>> h/w parts connected to SAKC board's extendable 40pins header to get
> 3.3V
> >>> supply( actually comes from 5V) to outside application.
> >>
> >> Yes, I'm trying to solve this issue, I think that we can use a single
> >> circuit Power On Reset + Transistor:
> >>                             TRANSISTOR
> >> USB_VCC-------------|S|           |D|----------- 5V
> >>                                                        |
> >>                                      |G|              |
> >>                                        |               |
> >> DC_WALL------|  POR |----------------------
> >>
> >>
> >> When DC_WALL = 0V  Transistor is ON so 5V = USB_VCC
> >> when DC_WALL >= POR's threshold => Transistor is OFF =>  5V = DC_WALL
> >>
> >>>
> >>> Also if SAKC comes with capability of having strong wide power range
> >>> input, this can make/let additional circuities connected to SAKC
> easiler and
> >>> more flexible with ONLY one DC adapter. Fg. real ROBOT industries works
> >>> around +12V or +9V supply. IMO if this can be true. SAKC will be more
> >>> stronger. Surely aside from cost evaluation.
> >>
> >> We can't provide all the possible voltages for all the possible
> >> applications. We can add an additional 5v regulator with a wide input
> range,
> >> but this increase the cost & the size.
> >> Carlos
> >>
> >>
> >> --
> >> Carlos Iván Camargo Bareño
> >> Profesor Asistente
> >> Departamento de Ingeniería Eléctrica y Electrónica
> >> Universidad Nacional de Colombia
> >> cicamargoba at unal.edu.co
> >>
> >> _______________________________________________
> >> Qi Developer Mailing List
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> >
> >
> > _______________________________________________
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>
>
>
> --
> David Reyes Samblas Martinez
> http://www.tuxbrain.com
> Open ultraportable & embedded solutions
> Ben NanoNote, Arduino, Openmoko
> Hey, watch out!!! There's a linux in your pocket!!!
>
> _______________________________________________
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>



-- 
Carlos Iván Camargo Bareño
Profesor Asistente
Departamento de Ingeniería Eléctrica y Electrónica
Universidad Nacional de Colombia
cicamargoba at unal.edu.co
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