Isaac,
Your schematic is nice. However I still not understand why do you need T1
and T2 when you could use a MOSFET without anti parallel diode for T1
(charger power .pdf). I'm assuming the VCC does not have the second supply
input.

"Transistors T1 and T2 are P-channel MOSFETs with very low Rdson. With both
transistors off, current cannot flow in any direction because of the
face-to-face transistors' body diodes."

thx,
Vasile

On Thu, Mar 12, 2015 at 2:31 PM, Isaac Marino Bavaresco <
isaacbavaresco@yahoo.com.br> wrote:

> I just checked my schematic and found that I used the LTC4088 together
> with an RT6150A and a PAM2401.
> That was the most economical solution I found. A single-chip solution
> from LT would be more expensive, so I used one step-up (PAM2401) and one
> buck-boost (RT6150A).
>
>
> Cheers,
>
> Isaac
>
>
> On 12/03/2015 00:11, Isaac Marino Bavaresco wrote:
> > That's what my circuit does, using the same button for powering-up and
> > for input.
> > The switch feeds the bases of two transistors with emitters to ground,
> > one collector goes to the power circuit and the other collector goes to
> > a MCU pin. A third transistor is operated by a GPIO of the MCU and its
> > collector is tied in parallel with the other transistor that commands
> > the power circuit.
> >
> > I use also an RC circuit coming from the external power input that
> > generates a pulse and turns on the circuit when external power is first
> > applied but allows the circuit to power itself off afterwards.
> >
> > For the buck-boost, Linear Technology has some nice battery management
> > chips (with what they call "PowerPath") with battery charger and severa=
l
> > boost and buck-boost circuits. I used one of them, don't remember right
> > now exactly which one.
> >
> > Check the LTC3566.
> >
> >
> > Cheers,
> >
> > Isaac
> >
> >
> >
> > On 11/03/2015 22:52, Lee Mulvogue wrote:
> >> Just been going back through Isaac's thread from 23/Feb as I'm looking
> at
> >> something similar
> >>
> http://www.piclist.com/techref/postbot.asp?by=3Dthread&id=3D%5BEE%5D+Char=
ger+and+power+circuit+for+mobile+equipmen&w=3Dbody&tgt=3Dpost&at=3D20150123=
104616a#104616a
> >>
> >> and have a couple of related questions;
> >>
> >> - if using a momentary button, switching to ground, to latch the power
> >> supply (MCU holding it there), is it possible to re-use that button fo=
r
> >> input purposes?  I currently have two buttons switching to ground used
> as
> >> inputs, but no latched power system.  I'd like to disable the buck-boo=
st
> >> on complete shutdown, but don't have room for additional switches, and
> >> double-pole switches of the style I'm using/need don't seem to exist.
> >>
> >> - what type of diodes were D1, D2, D3?
> >>
> >> - if I always need both 3.3V and 5V from a li-ion when in operation,
> with
> >> the ability to boost from a min of about 3.0V, is there much benefit t=
o
> >> using two buck-boosts, over one buck-boost to 5V and one LDO for the
> 3.3V?
> >>
> >> Thanks
> >> Lee
> >>
> >
> >
>
>
>
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