The LT3651 is a 1 cell 4A Li-Ion/Polymer battery charger that operates with input voltages up to 32V. An efficient monolithic average current mode synchronous switching regulator provides constant current, constant voltage charging with programmable maximum charge current. A charging cycle starts with battery insertion or when the battery voltage drops 2.5% below the float voltage. Charger termination is selectable as either charge current or internal safety timer timeout. Charge current termination occurs when the charge current falls to one-tenth the programmed maximum current (C/10). Timer based termination is typically set to three hours and is user programmable (charging continues below C/10 until timeout). Once charging is terminated, the LT3651 supply current drops to 85μA into a standby mode.The LT3651 offers several safety features. A discharged battery is preconditioned with a small trickle charge and generates a signal if unresponsive. A thermistor monitors battery temperature, halting charging if out of range. Excessive die temperature reduces charge current. Charge current is also reduced to maintain constant input current to prevent excessive input loading.The LT3651 is available in a 5mm × 6mm 36-pin QFN package.Float VoltageLT3651-4.14.1VLT3651-4.24.2VLT3651-8.28.2VLT3651-8.48.4VApplicationsIndustrial Handheld Instruments12V to 24V Automotive and Heavy EquipmentDesktop Cradle ChargersNotebook Computers