The AAT2554 is a fully integrated 500mA battery charger, a 250mA step-down converter, and a 300mA low dropout (LDO) linear regulator. The input voltage range is 4V to 6.5V for the battery charger and 2.7V to 5.5V for the step-down converter and linear regulator, making it ideal for applications operating with single-cell lithium-ion/polymer batteries. The battery charger is a complete constant current/constant voltage linear charger. It offers an integrated pass device, reverse blocking protection, high accuracy current and voltage regulation, charge status, and charge termination. The charging current is programmable via external resistor from 15mA to 500mA. In addition to these standard features, the device offers over-voltage, current limit, and thermal protection. The step-down converter is a highly integrated converter operating at a 1.5MHz switching frequency, minimizing the size of external components while keeping switching losses low. It has independent input and enable pins. The output voltage ranges from 0.6V to the input voltage. The AAT2554 linear regulator is designed for fast transient response and good power supply ripple rejection. Designed for 300mA of load current, it includes short-circuit protection and thermal shutdown. The AAT2554 is available in a Pb-free, thermally-enhanced TDFN34-16 package and is rated over the -40°C to +85°C temperature range.