| As the development of Bluetooth-Low-Energy,its power management module is facing high-er requirements.More than 90%of working time,Bluetooth device operates in standby mode or shutdown mode.Therefore,it needs its power management have high efficiency especially in ultra-low load condition to prolong the working time of battery.Here,an ultra-low power and high efficiency Buck converter is proposed to satisfy system requirements.The proposed ultra-low power Buck converter adopts the improved V2 control scheme.It is a variable on time controlled mode based on ripple mode control.It has two voltage-controlled loops,so that the load voltage regulation and power regulation are high,which improves the DC accuracy of output voltage and transient response speed.Its control mode can transfer form PWM mode to PFM mode automatically when load current decrease and inductor current is across ze-ro.Under ultra-load condition,Burst control mode is added which increases low load efficiency greatly.Adaptive on time control mode ensures the system working frequency fixed at different input voltages.The ripple compensation module ensures that the system operates in a stable state with low ESR output capacitance.The bandgap reference,current source and PWM comparator operates in subthreshold region in Burst mode,and the static current at that time is only 445nA.Integrated compensation network,power transistor and other devices make PCB area minimize a lot.The only external devices needed are inductor and output capacitor.This Buck converter is designed and layouted with Global Foundry 0.18?m process.The simulation results show that this system has outstanding power regulation and load regulation,which is only 0.03%respectively when input voltage is 3.6V,output voltage is 1.6V and maximum load current is 50mA.The highest efficiency achieves 90.7%when load current is 15mA.Even when load current is only 10?A,the system efficiency is higher than 70%.The static current is only 445nA. |
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