Design And Application Of LDO Based On Bipolar Process

With the improvement of semiconductor technology and the development ofportable electronic devices, as a kind of power management chip, the low-dropoutlinear regulator (LDO) with the advantages of small noise and ripples, simple structureand low cost has a considerably wide field of applications. LDO is also an effectivesolution to the problem of low efficiency of conventional linear regulators, and hasalready become mainstream direction in linear regulator research areas. A newgeneration of LDO develops toward low supply voltage, low power consumption, highefficiency direction. Compared with the CMOS process, the device adopting bipolarprocess has the advantages of low mismatch, higher power density and a smaller chipsize, and has a smaller parasitic capacitance so that it has a better transient responsecharacteristic, and can also provide greater driving current. Bipolar process occupies acertain position with its mature technology, high speed and driving ability.High power LDO based on the bipolar process is designed. Ultra-PNP is usedas adjusting tube, because it consumes relatively small quiescent current responsing tothe high load current. It provides3.3V output voltage, load current ranging from10mAto5A and500mV dropout voltage. In addition, over-temperature, over-current andover-voltage protection circuits are designed to ensure that the chip can work safely.Over-current or too low input voltage results in the output error identification signal.This chip has the advantages of having a simple peripheral circuit, low powerconsumption and high efficiency.First, this paper introduces the basic concepts, the working principles, the keymodule circuit structure, stability of the system and compensation methods, and thenelaborates on the performance parameters and system architecture of LDO to provide atheoretical basis for the specific circuit design.In addition, in accordance with the design specifications of LDO, the bandgapreference, the error amplifier, the comparator, the protection circuit and the adjustingtube of the LDO are designed and simulated. LDO system frequency compensation is discussed, analyzed and designed, and system loop stability is verified by simulation,as well as the output accuracy, quiescent current and conversion efficiency and otherindicators of system performance parameters.Finally, bipolar process technology is introduced，and the LDO physical layout isshowed and verified with LVS and DRC.This design uses CSMC2um bipolar technology, and is simulated and verifiedwith Hspice. The simulation results show that the LDO output voltage has a highaccuracy. The LDO has a0.28%load regulation and a linear a0.14%line regulation,output voltage drift is101ppm/℃from-55℃to150℃.