Design Of An Ultra Low Power DC-DC Converter With 350 NA Quiescent Current

The demand for high quality power management integrated circuits(ICs)is growing rapidly due to the development of Internet of Things(IoT).In wireless sensor network,wearable devices and other IoT applications,the power source is limited while the battery lifetime is extremely important,take smart meter as example,the target battery life is expected to be more than ten years,which imposes extremely stringent requirements on the power consumption of power management ICs.Thus an ultra lower power DC-DC step-down converter with 350 nano amphere(nA)quiescent current is proposed in this paper to extend the battery lifetime of IoT devices.Ripple based control,sub-threshold voltage design and other techniques are adopted in this design to minimize the power consumption while ensuring the performance of the chip.Quasi-V2 adaptive on-time(AOT)control is adopted in this ultra low power DC-DC converter,two voltage loops provide fast transient response and accurate DC load regulation,and the AOT mechanism improves the frequency stability in Pulse Width Modulation(PWM)mode.This control method supports PWM mode for medium and high load conditions and PFM(Pulse Frequency Modulation)for light loads,which also provides a seamless transition between PWM mode and PFM mode without an external control signal.In light load conditions,the system shuts down most of the power-consumed modules while the device is not switching,the remaining modules operate in sub-threshold region so the whole quiescent current of the IC can be reduced to 350 nA.Small-signal characteristics of the control are derived and verified with Matlab tool to guarantee the stability of this study.The IC has short circuit protection and Under-Voltage Lock Out(UVLO),in addition,the power transistors and feedback divider network are also integrated in the IC,which minimizes the number of external componentsThe DC-DC chip is designed with 6V 0.18 μm BCD process.Simulation results show that the system has excellent load transient response,the chip consumes 353 nA quiescent current while the device is not switching.Benefit from the ultra-low IQ,the system achieves conversion efficiency of 80%at 10μA load,the peak efficiency is up to 92%at 80 mA load.