A negative-voltage LDO with bidirectional enable

This article presents the design and implementation of a negative-voltage low-dropout linear regulator (LDO) with bidirectional enable functionality. Firstly, the fundamental architecture and operational characteristics of the conventional negative-voltage LDO are introduced. Based on the application scenarios of the negative-voltage LDO, the necessity for bidirectional enable is put forward. Subsequently, the traditional enable circuit and the proposed bidirectional enable circuit are demonstrated, and analyses are conducted for both positive-voltage startup and negative-voltage startup scenarios. Finally, the negative-voltage LDO chip is designed and fabricated in a 350 nm CMOS process. The test results indicate that the negative-voltage LDO can achieve bidirectional startup within the enable signal range of greater than 0.96 V and less than 5 V, as well as greater than -5 V and less than -0.9 V. Moreover, the enable circuit consumes a current of 873 nA during the positive-voltage startup process and a current of 219 nA during the negative-voltage startup process.