A programmable smart charger compatible to various load conditions is proposed in this paper. Since the proposed smart charger is compatible to various mobile devices having different rated voltage and power, it is convenient for carrying and easy to standardize many kinds of battery chargers. Moreover, since it uses the input impedance and built-in PMIC (Power management IC) of the load system to recognize the connection state and specifications of load system, hardware changes of load system is not only hardly necessary but it also features no addition communication cable and easy implementation. To confirm the validity of the proposed charger, the theoretical analysis and experiment results from a prototype compatible to three load conditions 5V/1A, 5V/2A and 12V/1A are provided.