Research And Design Of Synchronous Dual-output Switched Capacitor DC/DC Converter

Along with fast development of the modern integrated circuit (IC) technology, the market of portable electronic devices grows rapidly. It challenges the designer of power management circuits. For example, the DC-DC converters with high efficiency, small volume and low cost are strongly demanded by portable devices. However, the traditional PWM DC-DC converters can achieve good performance just while load current is over 500mA. In recent years, since the size of portable electronic devices is getting smaller and smaller, while the load currents as well as supply voltages are getting lower and lower, the inductorless charge pump converter based on switched capacitor attracts more attentions in the space constrained applications with 10mA to 500mA load current. It has become the mainstream power supply solution for handheld portable apparatus.In addition, SOC (System on Chip) composed of analog and digital circuits integrated on a same chip, which demands different supply voltages for the two circuits respectively especially in deep sub-micro integrated circuit, becomes the mainstream technology of modern IC. Therefore, the synchronous dual-output switched capacitor DC/DC converter, which supplies two different regulated output voltages, becomes new highlight of power supply solution. For this reason, this thesis proposed a synchronous dual output charge pump converter with step up and step down gains and completed it in system and circuits levels.Based on researching of different charge pumps that suit for DC-DC converters, the basic charge pump operation principle was given first and the main performance parameters were analyzed quantitatively. Then three regulation methods involving post regulation, pre-regulation and PFM regulation were discussed and compared. Through discussing the results, the PFM regulation method was adopted to meet the target of the system.The innovation of this thesis includes fly capacitor co-use idea, multi-gain mode technology, gain hopping technology, state machine and logic control way. The proposed charge pump converter could supply step up and step down regulated output voltages synchronously and share the driving capability between the two channels. The 5V step up voltage and 1.8V step down voltage with input voltage range of 2.0V to 3.6V could be generated. Both channels were capable of driving 100mA load current, and the peak value of efficiency reached 85% to 90%.After completing the system design, the design of functional building blocks were implemented in TSMC standard CMOS 0.35um process, which included low voltage bandgap circuit, oscillator, dead time setting circuit, state machine, logic control circuit, comparators, LDO with enable signal, UVLO and power output circuit. All blocks were designed and simulated under the environment of Spectre of Cadence. Simulation results showed that the system and circuits worked well. And almost all expected specifications were realized.