Hi Isaac,

I am just curious about your goals.
Your schematic has already 2 ICs, 2 MOSFETs, 1 transistor, 3 diodes and few=
 resistors, plus most likely all the decoupling caps that you did not show =
in your schematic. What is your price estimate for those, so we know your p=
rice target and then we can help.

Just my $0.02,
Jean-Paul
AC9GH


> On Jan 23, 2015, at 3:23 PM, Isaac Marino Bavaresco <isaacbavaresco@yahoo=
..com.br> wrote:
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> Hey Alan, thanks for the tip!
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> LT has some nice PMICs that almost fit the requirements, but (as
> expected) they are very expensive (US$8.22 @ 1, US$4.53 @ 100).
> While I don't find something less expensive I will keep trying a
> discrete solution.
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> Best regards,
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> Isaac
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> On 23/01/2015 13:58, alan.b.pearce@stfc.ac.uk wrote:
>> I would check the Linear Technology web site. They make charger ICs, and=
 also have an IC for controlling MOSFETs in an 'ideal diode' configuration,=
 although I am not sure the latter is appropriate for this. But the charger=
 ICs should be able to do exactly what you want, as it is a not uncommon re=
quirement (cell phones etc).
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>>> I need to design a mobile equipment operated by an 1-cell Li-Ion batter=
y.
>>> I want the equipment to be able to charge and operate simultaneously wh=
en
>>> connected to a power supply and operate on battery power when not
>>> connected.
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>>> Some restrictions:
>>> 1) I cannot afford the Vf drop of a diode from the battery to the circu=
it;
>>> 2) When the circuit is charging and power is suddenly removed, it must
>>> continue operating without any interruption;
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>>> I devised the attached circuit (PDF). I hope it performs as expected.
>> ...
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