A Low Voltage BUCK DC-DC Converter Scheme For Dynamic Voltage Scaling Applications

In today's consumer market, the portable equipment such as the smart phone, PAD, digital camera and so on, have been widely used all around world, which concentrate a variety of embedded system hardware and software technology hot spot areas, attracting lots of attention from technology industry. The prevalence of battery-operated portable devices creates a great demand for high-quality switching DC-DC converters. The desirable qualities generally include high efficiency, small volume, tight static, dynamic regulations and low electromagnetic interference (EMI) noise.With regard to efficiency, recently low-power VLSI technique named as dynamic voltage scaling (DVS) calls for a new type of"Adaptive Power Supply". In this research, the output voltage is required to track the reference voltage when the latter has a step change. This method can reduce unnecessary power consumption as much as possible while ensure normal operation of whole circuit even system. As a result, the new parameter, namely tracking time, is introduced to characterize the power supply's performance on speed during reference tracking.With the scaling of critical size in process technology and decrease of power consumption, the industry and market want to reduce production cost while hold long product endurance time. So these requirements need designers to do the circuit design in the lower and lower supply voltage. However, in the traditional digital CMOS ICs, the decrease of the supply voltage results in slow speed and small noise margin. These influences also occur in the research of DC-DC converter, which is one significant part of normal IC products. In this thesis, a quick-response DC-DC buck converter in 1.8V 0.18um standard CMOS process has been designed for 1.8V input voltage. In this design, a quick charge path switch is used to improve the up-tracking time against the slow trait in low voltage. In this way, with the same tracking time, the chip area can be reduced as much as 70%. What's more, a switching frequency control scheme called Adaptive Delay Compensation (ADC) is used to maintain the switching frequency at 830 kHz to within +/- 4.5% across the operation range, reducing EMI noise effectively.