A High Slew-Rate Push-Pull Output Amplifier for Low-Quiescent Current Low-Dropout Regulators With Transient-Response Improvement

• Published in: IEEE transactions on circuits and systems. II, Express briefs Vol. 54; no. 9; pp. 755 - 759
• Main Authors: Tsz Yin Man, Mok, P.K.T., Mansun Chan
• Format: Journal Article
• Language: English
• Published: New York IEEE 01.09.2007; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Amplifiers; Batteries; Capacitors; CMOS process; Compensation; Consumption; Councils; Degradation; Driving; Electric potential; Energy management; High slew rate; low-dropout (LDO) regulator; low-quiescent current; Regulators; Semiconductors; Stability; Tail; tail current; Voltage
• ISSN: 1549-7747; 1558-3791
• DOI: 10.1109/TCSII.2007.900347

A high slew-rate amplifier with push-pull output driving capability is proposed to enable an ultra-low quiescent current (Iq ~ 1muA) low-dropout (LDO) regulator with improved transient responses. The proposed amplifier eliminates the tradeoff between small Iq and large slew-rate that is imposed by the tail-current in conventional amplifier design. Push-pull output stage is introduced to enhance the output driving ability. Small dropout voltage (Vbo) with large-size pass transistor and ultra-low Iq can thus be used to minimize power loss of LDO regulator without transient-response degradation. The proposed amplifier helps to improve stability of LDO regulators without using any on-chip and off-chip compensation capacitors. This is beneficial to chip-level power management requiring high-area efficiency. An LDO regulator with the proposed amplifier has been implemented in a 0.18- mum standard CMOS process and occupies 0.09 mm 2 . The LDO regulator can deliver 50-mA load current at 1-V input and ~ 100-mV V DO . It only consumes 1.2 muA Iq and is able to recover within ~ 4 mus even under the worst case scenario.