Datasheet
The MAX1909 evaluation kit is an accurate and efficient multichemistry battery charger. It can charge three or four series Li+ cells with a current up to 3A. Charge current and input-source current are adjustable using on-board potentiometers. The output voltage is set to 4.2V ✕ the number of series cells in the battery pack. The number of series cells is jumper-selectable. The output voltage is adjustable between 4V to 4.4V (✕ number of series cells) by installing two resistors. The EV kit provides outputs to monitor the AC adapter current and the presence of an AC adapter. The MAX1909 automatically selects the power path for supplying power to the system by controlling two external P-channel MOSFETs. This decision is made based on the presence of an AC adapter.
User Manual
The MAX1909/MAX8725 are highly integrated control ICs that simplify the construction of accurate and efficient multi-chemistry battery chargers. The MAX1909/MAX8725 use analog inputs to control charge current and voltage, and can be programmed by a host microcontroller (µC) or hardwired. High efficiency is achieved through use of buck topology with synchronous rectification. The maximum current drawn from the AC adapter is programmable to avoid overloading the AC adapter when supplying the load and the battery charger simultaneously. The MAX1909/MAX8725 provide a digital output that indicates the presence of an AC adapter, and an analog output that monitors the current drawn from the AC adapter. Based on the presence or absence of the AC adapter, the MAX1909/MAX8725 automatically select the appropriate source for supplying power to the system by controlling two external p-channel MOSFETs. Under system control, the MAX1909/MAX8725 allow the battery to undergo a relearning or conditioning cycle in which the battery is completely discharged through the system load and then recharged. The MAX1909 includes a conditioning charge feature while the MAX8725 does not. The MAX1909/MAX8725 are available in space-saving 28-pin, 5mm × 5mm thin QFN packages and operate over the extended -40°C to +85°C temperature range. The MAX1909/MAX8725 are now available in lead-free packages.
