| The switch power possesses the advantages of compact size and high efficiency compared with conventional linear power which makes its wide application in the field of communication, computer, etc. In recently year, there is a rapid increasing market demanding for battery-powered portable equipments (such as PDAs, Mobiles, etc), which requires the DC-DC converter with high efficiency to boost the battery supply capability and good large signal property to satisfy the special demand of the CPU, DSP and flash memory.We build a synchronous rectifying switch power IC with high efficiency and good load characteristic following the requirements of the battery-powered portable equipments. All control circuits are integrated(including power MOS) in the IC except the output low-pass filter, two optional operation modes: PWM and PFM are available. The switch power will operate at CCM condition when circuit is set to PWM mode. When PFM mode is selected for the operation mode, the switch power will still operate at PWM condition with the high load, the system will cancel the PWM mode and enter the PFM mode only when the load is drop to a certain threshold to boost the operation efficiency at light load, make the IC has high efficiency within wide load range. The synchronous rectifying and low power sampling technology is used to reduce the power consumption, flexible external loop compensation, error amplifier output clamp are adopted for better system large signal response. The piecewise slope compensation technology is employed to minimize the consequence of over compensation.The sensor resistor is externally connected,which realize output voltage programmable. The overheat protection and under voltage protection modules are integrated in the die to allow the reliable operation of the system.The circuit was simulated via Hspice based on CSMC 0.5um process whose results indicates the all modules have meet the requirements and the efficiency can go up to 95% under PWM mode and stay above 90% under PFM mode when the load resistance... |
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