超級電流鏡用於低壓降線性穩壓器以達成快速暫態響應

Abstract

隨著可攜式電子產品蓬勃的發展，電源管理系統需要有較好的穩壓效能和較高的能量效率。電源管理系統被廣泛應用在許多方面，例如可攜式電話、行動電視、數位相機和個人數位助理…等，因此，如何有效使用和分配電池有限能量是電源管理系統重要的課題。可攜式產品通常需要使用電源管理系統控制不同功能單元的驅動使得系統能正常且有效率的工作，對於電源管理系統來說，低壓降線性穩壓器是低雜訊，低複雜度，且便宜的應用單元。 近年來，對於高效能低壓降線性穩壓器的需求，日與劇增，例如高的負載調節率、低的功率消耗和高的電源拒斥比…等。因此，可攜式產品現今正面臨關鍵的問題，由於傳統的低壓降線性穩壓器並不能同時達到在負載變動時有快速的負載暫態響應和低的功率消耗。然而，不管多快的負載暫態響應可以達到，低壓降線性穩壓器都不能有不穩定的狀態，換句話說，低壓降線性穩壓器必須能夠穩定在所有負載條件下，這通常需要用頻率補償的方式來克服。 本論文將提出一個新的頻率補償方式，能夠將此快速負載暫態響應的低壓降線性穩壓器穩定，使用TSMC 0.35um2P4M的製程。此低壓降線性穩壓器具有適應性偏壓電流的架構，可以有效的到達快速負載暫態響應，其利用超級電流鏡電路來完成，使得負載電流從輕載變重載的暫態穩定時間少於1us。然而，此低壓降線性穩壓器會遭遇到穩定度問題，利用本論文提出的頻率補償方式可以使此低壓降線性穩壓器穩定。

With the growing demand for portable devices, power management systems need to have better regulating performance and higher energy efficiency. Power management systems are used in many applications such as cellular phones, mobile TV, camera recorder and PDAs, etc. Therefore, how to use the battery energy efficiently is the most concerned problem. Portable applications often need multiple voltages controlled by a power management IC to power up many functional blocks. For power management system, Compare with the switching regulators, low-dropout linear regulator (LDO) is less noisy, less complex, and cheaper. In recent years, the demanding for high performance linear regulator is getting increasing, such as high load regulation, low power consumption and high power supply rejection, etc. The critical problem in modern portable applications is that the conventional low-dropout regulator can’t reach both the high-speed load transient response for load variation and low power consumption. Furthermore, no matter how fast the load transient response, the low-dropout regulator can’t fall to unstable state. In other words, the low-dropout regulator has to be stable for all load conditions and frequency compensation is usually needed to stabilize the regulator loop. A frequency compensation method for low-voltage fast transient-response low-dropout regulator using TSMC 0.35um2P4M CMOS process is presented in this paper. It features a current-efficient adaptively biased regulation scheme using a low-voltage high speed super current mirror (SCM). This low-dropout regulator can achieve fast transient-response and the settling time is less than 1us from light to heavy load. However, this low-dropout regulator has a stability problem. By using this frequency compensation method, the loop can be stable for all load conditions.