can i charge my mobile phone with the current obtained from output of LTC3108 3.5mA
While I don’t have the specifications of your cell phone , it is unlikely that this will charge your phone with that amount of current.
if battery capacity is 1800mAh…do i need external power management circuitry from the output of LTC3108 which is 5V and 3.5mA
There are a couple of issues here. The first is a charge management circuit that would prevent overcharging. This should be built into your cell phone. The question is what is the input voltage and current required by your cell phone.
The second is the time it takes to charge a 1800mAh battery with a 3.5mA charge providing there are no losses in the transfer from the chip to the battery itself. Most cell phone chargers operate on a 5V 500mA or higher circuits.
if my input source to LTC3108 is 500mV and i am boosting the voltage to 5V , P=VI, P= 5V3.5mA which is 17.5 mW and this power is not sufficient to charge a mobile phone…
It would be best to check what your phone required to charge the battery, as stated before most of the time you would need at least 500mA to charge the battery. Sorry but the 3.5mA is not enough.