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Li-ion Battery monitor

Question asked by ChaitanyaB on Aug 9, 2011
Latest reply on Aug 19, 2011 by ChaitanyaB

Hi,

 

I am having 5V Adapter,Battery charger,Battery, load switch and Buck Boost after load switch and uC.

 

I am designing with ADM706SAR, I am having some design issues:

 

I am using the PFI and PFO for power fail.I need to shut down my DC to DC regulator(buck-boost) when the battery is low. I have kept the PFI threshold at 3.2 volts.When input voltage goes below, the PFO is activated and uC gets an  interrupt.It will close its activities and stay idle.

 

However I need to shut down the DC to DC also,Earlier I have planned for delayed PFO to the DC to DC's Shut down pin however that makes the Reset IC to be provided with unregulated battery output.

In that case the VCC will be unregulated(4.8V from Charger and 3.2 volts from battery) and my RESET signal might get affected.

As the battery will be 3.0 and  DC to DC will be in shut down phase, when the charger will be applied the PFO will be high as the input changes  from 3.0 to 4.8V however the RESET will not be generated as it requires input to reach 2.85V(this is not possible with unregulated connection of Li-ion).

I am attaching my schematic.

 

I think there is no open drain output available with PFI facility in supervisory selection and hence I need to put a Zener over RESET as it will be pulled to 4.8V in case of Charger.

 

Pls guide me.

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