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Tham khảo tài liệu 'adaptive techniques for dynamic processor optimization_theory and practice episode 1 part 7', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Chapter 5 Adaptive Supply Voltage Delivery for U-DVS Systems 109 5.3.2 DC-DC Converter Topologies for U-DVS 5.3.2.1 Linear Regulators Low-dropout LDO linear regulators 22 are widely used to supply analog and digital circuits and feature in several standalone or embedded power management ICs. The main advantage of LDO s is that they can be completely on-chip occupy very little area and offer good transient and ripple characteristics together with being a low-cost solution. Using LDO s for U-DVS however is detrimental because of the linear loss of efficiency in an LDO. A linear regulator essentially controls the resistance of a transistor in order to regulate the output voltage. As a result the current delivered to the load flows directly from the battery and hence the maximum efficiency achievable is limited to the ratio of the output voltage to the input voltage. Thus the farther away the load voltage is from the battery voltage the lower the efficiency of the LDO. This hampers the potential savings in power consumption that can be achieved by lowering the voltage through DVS. 5.3.2.2 Inductor-Based DC-DC Converter The most efficient DC-DC voltage converters are inductor-based switching regulators which normally generate a reduced DC voltage level by filtering a pulse-width modulated PWM signal through a simple LC filter. A buck-type regulator can generate different DC voltage levels by varying the duty-cycle of the PWM signal. Given ideal devices and passives an inductor-based DC-DC converter can theoretically achieve 100 efficiency independent of the load voltage being delivered. Moreover in the context of DVS systems scaling the output voltage can be done with completely digital control circuitry 21 which consumes very little overhead power. An implementation of an inductor-based switching regulator for minimum energy operation is described in Section 5.3.3.1C. While buck converters 23 can operate at very high efficiencies 90 they generally require off-chip .
