+-----------> to uP Vcc
                 |
                ---
                /  Shottky Diode
                ---  (low Vf)
                 |
    +---xxxx-----+------------> to uP A/D
    |   Resistor                 input.
    |
   ---
    -
   ---  1.6V Batt
    -
    |
    | 
   ---
   ///