BL8531C series are CMOS-based PFM step-up DC-DC Controller with low supply current and high output voltage accuracy. Quiescent current drawn from power source is as low as 6uA. It is capable of delivering 500mA output current at 4.0V output with 2V input Voltage. Only four external components are necessary: An inductor, a Schottky diode, an output filter capacitor and a NMOSFET or a NPN transistor All of these features make BL8531C series be suitable for the portable devices, which are supplied by a single battery to four-cell batteries. BL8531C has a drive pin (EXT) for external transistor. So it is possible to load a large output current with a power transistor which has a low voltage dropout. BL8531C integrates stable reference circuits and trimming technology, so it can afford high precision and low temperature-drift coefficient of the output voltage. BL8531C is available in SOT-23-3, SOT-23-5 and SOT-89-3 packages which are PB free. And in SOT-23-5 the device can be switch on or off easily by CE pin, to minimize the standby supply current.