Hello All,

I want to measure a 14.8V LiPo battery and it has a cutoff voltage of 12.8V at which I want to disable the motor driver and other peripherals...Since the MCU ADC's vref 3.3v, I used a voltage divider to divide the 14.8V with100Kohm and 20 Kohm, these resistors gives 2.96V for 14.8V and 2.56V for 12.8V...I read the TIVAC123 datasheet for ADC input resistance, which is 2.5Kohm only...If you calculate the thevenin resistance for the voltage divider, it is approximately 16.6Kohm...The source impedance the TIVAC123 wants is less than 500Ohm but what I am feeding is 16.6Kohm...The impedance mismatch needs a opamp based buffer in between the voltage divider and ADC...My question is that, should I use a RC filter at the input the OP-AMP?.If yes, what cut-off frequency I should select as the input is battery voltage?.what op-amp to do this job?

Thanks,

Muthu