Design Of Power Management Unit For Complex Load

With the change of the times and the development of science and technology,electronic devices are widely used in various fields.Wearable and portable electronic devices are now widely used in communications,health care,entertainment,tracking and security applications.These electronic devices are developing towards miniaturization and complexity,which makes the power supply for these electronic devices more diversified and systematic.Power management IC has become a key factor limiting the further miniaturization and intellectualization of electronic devices.The power management unit integrates several power management IC and manages them systematically.Therefore,the power management unit is more suitable for power management of most complex electronic devices.According to the complex load operation provided by customers,this paper determines that the designed power management unit contains two Bucks and two LDOs,and completes the design of the overall structure and logical control of the power management unit.Through the analysis of LDO,the gain and pole of the loop are calculated,and the stability of the loop is designed.The design of the LDO system covering a variety of functions is completed.Through the analysis of Buck’s control mode and small signal model,it is determined that the Buck structure is a valley current mode self-adaptively constant on-time Buck controlled by double phase-locked loops.The Buck loop is optimized and compensated,which speeds up the step transient response of load.Then the structure analysis,model deduction,specific sub-module design and loop compensation design of Buck’s external phase-locked loop are carried out.The influence of the internal phase-locked loop on Buck’s switching frequency through the self-adaptive on-time module is also analyzed.Finally,the design of valley current mode self-adaptive constant on-time Buck controlled by double phase-locked loop is completed.Combining the LDO and Buck,a power management unit for complex load is designed and verified by streaming chip.The power management unit designed in this paper is based on 0.18μm BCD process.The input voltage range is 5V-32 V,the output voltage range is 1.2V-28 V,and the maximum single load current is 2A.In the absence of external clock access,it can generate and operate at 1 MHz frequency,and the internal Buck 90° staggered operation,which can be cascaded,reducing the voltage ripple of the power bus.When the loads are switched between full and empty loads periodically,the ripple is only 3%.The transient response time of Buck load jumping from empty to 1.9A heavy load is only 11.84μs,which is 10 times faster than that of the traditional Buck load step,and is almost close to the limit speed of this topology.Not only does the input and output voltage work in a wide range,but also the transient step response of the load is very fast,which meets the application requirements of complex loads.