A Design Of High-precision LDO Linear Regulator

With the development of mobile electronic devices, like the popularity of mobile phones and tablets in the globe, as well as the rise of wearable equipment industry in the future, the status of the power management technology is increasingly important. Being sensitive to the noise of power, analog circuit requires purer power supply environment. LDO, one of power management chips, is attached increasingly great importance, because of its such advantages as simple structure, small size, high power supply rejection ratio, low power consumption, and being suitable for mobile phones and other wireless mobile devices. However, most high-end chips are made by foreign countries. Therefore, developing China’s own LDO linear regulators is of great significance.The Low Dropout Regulator described in this paper contains such four main modules as Band gap Reference module,Error Amplifier module,Pass Element module and Feedback Net module, as well as some auxiliary circuits. What presented in this papter are the basic structure and principle of the LDO linear regulator, its key performance indicators, analying the balance of several performance indicators through the analysis of a classic structure, briefing the difficulties of LDO’s loop stability and some simple methods for frequency compensation, and finally based on the technology of Huahong 0.35 μm BCD designing a LDO linear regulator with high precision and adjustable output voltage. The output voltage ranges from 0.8 V to 3.6 V and has the function of programmable soft start with about 100 μs of the minimum start-up time, which can reduce the surge current during startup and the stress of the power supply. By an external bias supply support, the input voltage can be as low as 0.9V, with very low dropout voltage and excellent transient response, and the dropout voltage of input voltage is only tens of millivolts. The chip is stable without output capacitor. Its function of power good can be used to indicate the value of VBIAS and VOUT selectively. Under the protection of over-temperature protection circuit, the chip can operate normally with the temperature from-40 ℃ to + 125 ℃, and hysteresis is an extra protection. In case excessive current burn up chips, the current limiting protection circuit will start and stop the working chips when current exceeds the set value. Superior performances of the LDO linear regulator are suitable for different types of power supplies and electronic equipment.Finally, circuit simulation is carried out with Cadence Spectre. The expected design goals of the circuit can be achieved in the simulation, including a reference voltage of 0.8V, the current limit from 3.8A to 5.5A, shutdown temperature of about 159 ℃, and the recovery temperature of about 145 ℃. Besides, the chip layout design and its package are also presented in this paper. The chip uses small QFN package. Finally, a highly compact overall solution size comes into being. Enjoying such advantages as high precision, low power consumption, simple external circuit, reducing the cost, saving the area, strong capability to regulate the load, and being suitable for various application scenarios, the LDO linear regulator is of high market value.