Design 1 is characterized at −40°C, +25°C, and +85°C, accepts input voltages from 3V to 5.2V, and can deliver output currents up to 10mA. It uses a low power consumption charge pump to drive the transformer at 50kHz frequency. A low switching frequency helps to achieve a uniquely high efficiency even at much lower output power levels, ranging from some tens of milliwatts down into the sub-milliwatt range. This design is able to provide more than an 85% efficiency for a 5V input operation at 15mW to 50mW of output power and more than 80% efficiency for a 3.3V operation at a 3mW to 20mW power level.