The CST9201 series is a high voltage，ultralow-power，low dropout voltage regulator. The device can deliver 350mA output current with a dropout voltage of 350mV and allows an input voltage as high as 55V. The typical quiescent current is only 2µA. The device is available in fixed output voltages of 1.8,2.5,2.8,3.0,3.3,3.6,4.0,4.2,4.4 and 5.0V.The device features integrated short-circuit protection、thermal shutdown protection and CE function enables the output to be turned off.Although designed primarily as fixed voltage regulators, The limiter‘s feedback circuit also operates as a protect for the output current limite, the device can be used with external components to obtain variable voltages.