Power from USB & DC Adapter (was Re: Design Files/Gerbers of SAKC V2)
cicamargoba at gmail.com
Fri Jul 30 10:44:20 EDT 2010
On Fri, Jul 30, 2010 at 8:53 AM, Adam Wang <adam at sharism.cc> wrote:
> 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.
> 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
> 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:
USB_VCC-------------|S| |D|----------- 5V
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 Iván Camargo Bareño
Departamento de Ingeniería Eléctrica y Electrónica
Universidad Nacional de Colombia
cicamargoba at unal.edu.co
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