As the complexity of mobile phone is increasing, the need for sophisticated power management in a mobile phone is also increasing. Role of power management is increasing with the reduction of battery voltage. In a GSM phone, several LDO are present to cater the needs of several subsections like, R.F, analog base band, digital base band, audio, display circuits etc. This project identifies the requirements of LDO for each sub section and design issues are discussed in detail. A new buffer circuit is presented to give constant phase margin at all loads. High accuracy is required for RF section LDO. So many architectures are presented along with very high loop gain LDO architecture. Their performance is thoroughly compared. Nested miller compensated LDO is proposed and is compensated well to yield good transient performance. In 0.35 μm CMOS process, NMC LDO regulator supplies an output voltage of 2.8 V, while the input voltage ranges in between 3 V to 4.2 V. Drop out voltage is 100mV. Subjected to an output voltage ripple of 100mV. The line regulation and load regulation of this regulator are less than 0.001%. All the circuits are simulated and the results are presented.
Volume 11 | 07-Special Issue