In this paper, a standalone output current sensing module for CMOS low dropout linear voltage (LDO) regulator with PMOS as pass device is proposed. The main purpose of current sensing is to create an overcurrent protection or to limit the output current value in certain applications. Based on I-V conversion in which the supply voltage varies from 2.7V -4.2V, the current clamp value varies from 178mA to 270mA in the case of 200mA load limiting. The proposal has been successfully fabricated using a CMOS technology, and verified through the correct operation of a power management prototype chip.

In this paper, a resistance-less over-current sensing circuit using current-voltage conversion technique for CMOS low dropout linear voltage (LDO) regulators with PMOS as pass device is proposed. The scheme of this over-current sensing uses the I-V conversion technique. This improvement results in an elimination of the body effect and reduces the deviation of the current limiter. The resulting current clamp value only varies from 190 to 250 mA when the supply voltage varies from 2.7 to 5 V. The total quiescent current of the LDO is 3.51 uA at the 5 V supply voltage. The current consumption of the overcurrent sensing circuit is about 1 uA.

A low dropout (LDO) linear voltage regulator, dubbed TH7150, is designed and reported. TH7150 is a power management device for analog chips, operating at low quiescent current (100uA), low voltage supply (1.6-3.6V), with low dropout voltage (200mV), and capable of driving 150mA output current. Its output voltage is programmable by logic control and also manually adjustable. It features protection measures for overheating and overloading and monitoring for the output voltage to prevent a dropout greater than 10% of current value. The chip is designed to be fabricated using 0.35 um process. It can be used as a standalone chip or integrated in a power supply chip for portable devices such as Smart phone, cell phone, Ipod, digital camera etc.