Method and apparatus for battery charging based on battery capacity and charging source constraints

A battery charging circuit comprising:

• a control circuit configured to:
• select a first mode of operation for a first type of charging source and select a second mode of operation for a second type of charging source;
• set a charging current and a termination current in proportion to a battery's capacity when operating in the first mode;
• and
• set the charging current according to a charging source constraint, while still setting the termination current in proportion to the battery's capacity, when operating in the second mode;
• and
• a charging circuit operatively associated with the control circuit and configured to provide said charging and termination currents to the battery under control of the control circuit;
• and
• a sense circuit configured to:
• generate a first sense signal that is proportional to battery current, with a sensitivity established by a first programmed value set in accordance to battery capacity;
• and
• generate a second sense signal that is proportional to battery current, with a sensitivity established by a second programmed value set in accordance to the charging source constraint.

A method of charging a battery comprising:

• setting charging and termination current magnitudes according to battery capacity, if operating in a first mode;
• setting charging current magnitude according to a charging source constraint, but setting termination current magnitude according to battery capacity, if operating in a second mode;
• and
• selecting the first mode if a first type of charging source is used, and selecting the second mode if a second type of charging source is used;
• wherein setting the charging current magnitude according to the charging source constraint comprises controlling the magnitude of the charging current by comparing a second sense signal to the first or a third voltage reference, and generating the second sense signal by directing a second current that is proportional to battery current into a user-settable second program resistor whose size is selected such that the voltage of the second sense signal is at or about the voltage of the first or third voltage reference when the battery current is at a desired source-constrained current magnitude.