Thx Isaac,
I knew the recommended design with back to back mosfets.
http://www.irf.com/technical-info/whitepaper/pcime2001final.pdf

Indeed, without internal diode is almost impossible to find some...
Vasile

On Sun, Mar 15, 2015 at 3:28 PM, Isaac Marino Bavaresco <
isaacbavaresco@yahoo.com.br> wrote:

> Vasile,
>
>
> The schematic I attached to the original message was just my first
> sketch. My final solution is quite different.
>
> I don't know of any good performance MOSFET transistors without the body
> diode. The diode is a side-effect of the manufacturing process and would
> not be easy to remove without impairing device performance. Even the
> chip manufacturer's schematic designs suggest using two back-to-back
> MOSFETS for battery chargers, for instance.
>
> Isaac
>
>
> On 15/03/2015 09:15, embedded systems wrote:
> > 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 o=
ne
> >> 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 an=
d
> >>> 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 it=
s
> >>> 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 fir=
st
> >>> applied but allows the circuit to power itself off afterwards.
> >>>
> >>> For the buck-boost, Linear Technology has some nice battery managemen=
t
> >>> chips (with what they call "PowerPath") with battery charger and
> several
> >>> boost and buck-boost circuits. I used one of them, don't remember rig=
ht
> >>> 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 looki=
ng
> >> 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 pow=
er
> >>>> supply (MCU holding it there), is it possible to re-use that button
> for
> >>>> input purposes?  I currently have two buttons switching to ground us=
ed
> >> as
> >>>> inputs, but no latched power system.  I'd like to disable the
> buck-boost
> >>>> on complete shutdown, but don't have room for additional switches, a=
nd
> >>>> 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
> to
> >>>> using two buck-boosts, over one buck-boost to 5V and one LDO for the
> >> 3.3V?
> >>>> Thanks
> >>>> Lee
> >>>>
> >>>
> >>
> >>
> >> --
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> >> http://mailman.mit.edu/mailman/listinfo/piclist
> >>
>
>
>
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