I have low power system which requires dual batteries to overcome the loop holes in the current system. Currently I have two batteries: Primary Battery Li-Ion 3.7V 1800mAh and a secondary battery Li-Ion 3.7V 560mAh. Both these batteries are connected to a load sharing circuit wich uses LTC4413 IC to control the switching between batteries. Basically what LTC4413 does is it constantly compares the voltage of the two batteries and keeps switching them ensuring both batteries discharge at the same rate.
But my application need is different. I am trying to design a circuit that only switches to back up battery under two conditions: 1)If primary battery is disconnected OR 2)If the voltage of Primary Battery is lower than 3.3V. Ideally I would like to have a STATUS pin which can transmit information (Low/High) to the uC regarding the which battery (Primary or Secondary) it is connected too.
During my research on internet, I have come across several circuits that can switch from battery 1 to battery 2 in absence of battery 1 but the 3.3V condition is vital and challenging. I am also trying to implement without a uC to control the switching. However if a uC is present with very low power characteristics in order of uA, I might use it as a last resort.
I would be obliged if somebody can suggest an IC that can do the job or circuit with low power loss.