The MAX1615/MAX1616 are micropower, SOT23-5 linear regulators that supply always-on, keep-alive power to CMOS RAM and microcontrollers (Cs) in systems with high-voltage batteries. Key features include wide input voltage range, low dropout voltage, and low quiescent supply current. Despite a miserly 8A (max) no-load supply current, the MAX1615/MAX1616 have excellent line-transient response and AC power-supply rejection ratio. They provide a clean, fixed 5V or 3.3V output (MAX1615) or an adjustable 1.24V to 28V output (MAX1616), even when subjected to fast supply-voltage changes that occur during the switchover from battery to AC adapter input power. The space-saving SOT23-5 package has excellent thermal characteristics and tolerates up to 571mW of power dissipation. Fault protection is provided by internal foldback current limiting and thermalshutdown circuitry. The MAX1615/MAX1616 are now available in lead-free packages.