The mission when designing the C8051F9xx product family was to significantly reduce the amount of energy needed for typical battery operated devices. In order to accomplish that goal the C8051F912 needed to offer the lowest power sleep and active modes, operate over the full battery range, and wake-up quickly. Having ultra-low sleep current is vital for applications with a small power budget. Systems with battery-operated wireless nodes (RFID, security, smart metering, etc.) wake up periodically, quickly perform measurements, transmit data and then go back to sleep to conserve power. In sleep modes, the C8051F9xx enters an ultra-low current state, preserving the contents of all the registers and SRAM. The real-time clock (RTC) is active so the MCU can wake up periodically using either the internal low power oscillator (C8051F912/02 only) or an external crystal source. Many products wake-up periodically to sample a sensor output using the on-chip ADC. It is important to allow enough time for the analog circuitry to settle in order to take a valid ADC measurement. The C8051F912 can wake-up from the sleep mode with the analog circuitry settled in less than 2 uS. That is fifteen times faster than the closest competitor allowing the C8051F912 to capture the necessary sensor output and go back to sleep before the competition can start a valid capture. Lastly, the C8051F912 requires half the current consumption compared to the competition when operating with new batteries (3.0V). This eco-friendly benefit provides for much longer battery lifetime.