Charge Pump Moves External Cap On-Chip

To save pc board space in size-constricted power supplies such as are used in notebook computers, PDAs and cell phones, SC1460 Capless charge pump moves the capacitor required by pumps from an external, on-board location to on-chip. Charge pump capacitors, called flying caps, are usually employed externally because of their large size. SC1460 was able to integrate the capacitor internally because its high,8-MHz operating frequency (at 2.5V input typical) allowed use of a smaller cap- input and output filter caps as small as 0.22 µF and 47 nF, respectively, can be used. Two models of the new charge pumps are available: SC1460-3.3, which provides a regulated 3.3V from a 2.5V input and SC1460-5.0, offering 5V from a 3.3V input. Voltage accuracy for both devices is ±4%. The tiny, 3-pin SOT-23 package delivers 5 mA (typical) and a quiescent current of 100 µA.