The MAX1870A step-up/step-down multichemistry battery charger charges with battery voltages above and below the adapter voltage. This highly integrated charger requires a minimum number of external components. The MAX1870A uses a proprietary step-up/stepdown control scheme that provides efficient charging. Analog inputs control charge current and voltage, and can be programmed by the host or hardwired. The MAX1870A accurately charges two to four lithiumion (Li+) series cells at greater than 4A. A programmable input current limit is included, which avoids overloading the AC adapter when supplying the load and the battery charger simultaneously. This reduces the maximum adapter current, which reduces cost. The MAX1870A provides analog outputs to monitor the current drawn from the AC adapter and charge current. A digital output indicates the presence of an AC adapter. When the adapter is removed, the MAX1870A consumes less than 1A from the battery. The MAX1870A is available in a 32-pin thin QFN (5mm x 5mm) package and is specified over the -40 C to +85C extended temperature range. The MAX1870A evaluation kit (MAX1870AEVKIT) is available to help reduce design time.