| With the development of wireless communication and semiconductor manufacturing technology, the portable electronic devices such as mobile phone, MP3, digital camera, and GPS navigation system have been developed rapidly. Furthermore, the customers'need becomes diversified and comprehensive. They desire not only the multifunction but also long battery life, compact size, and low cost. Against these requirements, a high efficiency power management unit (PMU) is needed to converter and regulate the supply voltage from the Lithium battery into different voltages for each module in the portable device using different methods according to the requirement. Therefore, the power management integrated circuits (PMIC) has became into the most fundamental and important part in the portable electronic devices.There are three basic types of PMIC: Switched-mode DC-DC converter, LDO (Low Drop-out Voltage Regulator), and Charge-pump. This paper sets forth the operating principles of switched-mode DC-DC converter, LDO, and charge-pump, respectively, aiming at achieving the feasibility design methods for PMIC. According to these methods, we can optimally design different kinds of PWIC. In practical applications, we can expediently design the appropriate PMIC based on these principles, so as to shorten the design cycle.For the switched-mode DC-DC converter, this paper has given the DC and AC modeling of the boost converter. A comprehensive analysis of power losses has been done according to the DC steady-state equivalent circuit, and then, the efficiency optimum schemes basing on PWM and PFM are proposed. The system transfer function and system stability are discussed according to the AC small-signal equivalent circuit. The purpose of analyzing these modeling is to provide a feasibility design methods for high efficiency boost converter design, and then, we can choose befitting efficiency optimum scheme for boost converter on the basis of load condition and modulation mode. In order to verify the correctness of theoretical analysis for DC-DC converter, two boost converters have been designed. One is high efficiency true-shutdown boost converter; the other is luminance-regulated white LED driver.Before the circuits design of the true-shutdown boost converter, we have modeled the boost converter under DCM using state-space averaging method firstly. And then, the feasibility of this design is verified by Matlab. An isolation power MOS is employed in the power stage to realize the true-shutdown aiming at reducing quiescence current and improving system efficiency. The minimum off-time PFM control and current-limited technique are adopted in the control circuit. The PFM control strategy can improve system efficiency at light load condition, and the current-limited technique can turn the system into a dual-loop control system in order to improve system stability. From the simulation results, the output voltage of the converter can be well stabilized at 15V (preset value) with a 220mV ripple, when the input voltage ranges from 2.7V to 5.5V. Furthermore, the line regulation and load regulation of the converter are 0.1%/V and 0.026%/mA, separately. Therefore, this boost converter can be used as a driver for light load conditions or medium load conditions.The design purpose of luminance-regulated white LED (WLED) driver is to provide a simple control circuit for DPWM, compared with conventional DPWM controllers which employ complex ADC and DSP architectures. In this case, the complexity and cost of the system can both be reduced. The DPWM and PSM are combined to improve the efficiency. The PSM can lower down the effective switching frequency, as well as the power losses. According to these specifics, the driver is designed using 0.6μm CMOS process. The DPWM controller is simply realized by an up/down counter and a duty-cycle modulator, without any ADC and DSP. The up/down counter is composed of several D flip-flops and basic logic units. Moreover, the driver can drive two independent WLED strings in parallel, and each WLED strings can have up to 6 WLED in series. The dimming control can be achieved by analog mode and digital mode. The simulation results illustrates that the maximum efficiency of the driver is 88% and the output voltage ripple is 40mV. Besides, the two WLED strings match well, when the load condition or power supply changes. Basing on the characteristics of the driver, it can be applied to backlighting for portable devices, one WLED string for keyboard, and the other for liquid crystal display (LCD) panel.For LDO, this paper has discussed the transient response and small-signal performance of the conventional LDO. According to the discussions, we know there is a large off-chip output capacitor in conventional LDO, in order to overcome this disadvantage, the off-chip capacitor-free LDO is proposed in this paper. Meanwhile, in order to achieve the same performance of traditional LDO, the transient response enhancement network and miller compensation circuits are introduced into the off-chip capacitor-free LDO. By analyzing the system transfer function and pole-zero positions, it is necessary to abortively design the off-chip capacitor-free LDO aiming at achieving faster transient response and more stable system. Finally, the off-chip capacitor-free LDO is designed using Chartered 0.35μm 3.3V CMOS process. It only needs a 2.5pF internal compensation capacitor and a 100pF load capacitor. For a pulsed load current from 0.5mA to 50mA, the proposed LDO can recover within 3μs and a less than 130mV deviation is recorded on the output of the LDO. Its simple structure and small chip area are additional advantages for full on-chip power management solution.For charge-pump, this paper describes the operating principle firstly, and then introduces the voltage-doubler (a type of boost charge-pump) in detail. Based on the principle of voltage-doubler, a WLED driver is designed. The driver can adaptively switch voltage-doubler (2×charge-pump mode) and LDO (1×charge-pump mode) according to the supply voltage and load current. The purpose of this adaptive mode changing strategy is to improve the power efficiency. Furthermore, in order to prevent frequency change between two modes under some special circumstances, hysteresis is designed in mode control circuit. From the simulation results, we can see the system efficiency is 95%, and output voltage ripple is 95mV, with 220mA load current and 3.6V supply voltage. Besides, the driver can drive a 1.1A maximum load current, which can be applied in digital camera for flash damp or in LCD panel.This paper not only has analyzed and designed several PMIC, but also researched the punchthrough enhanced phototransistor. The punchthrough enhanced phototransistor is proposed basing on the conventional phototransistor with a punchthrough base. The proposed phototransistor, which is completely compatible with standard CMOS process, is a simple lateral structure phototransistor combined with a normal phototransistor and a punchthrough transistor. Compared with conventional phototransistor with a punchthrough base, the proposed phototransistor has lower dark current and higher optical gain under weak light condition. The proposed phototransistor is fabricated with CSMC 0.5μm CMOS process. The measurement results indicate that, for a 60μm2 device, the operating voltage of the device is only about 2V, and the dark current is about 1μA. When the incident optical power density is 1.25×10-8W/cm2, the optical gain can achieve 9.4×106. The proposed phototransistor is not only aiming at high optical gain and low dark current, but also aiming at realizing the compatibity with standard CMOS process without any other special process step. With these characteristics, the proposed phototransistor can easily integrated with other auxiliary circuits on a monolithic chip, so as to lower the cost.
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