Design of low-power analog drivers based on slew-rate enhancement circuits for CMOS low-dropout regulators

• Published in: IEEE transactions on circuits and systems. II, Express briefs Vol. 52; no. 9; pp. 563 - 567
• Main Authors: Hoi Lee, Mok, P.K.T., Ka Nang Leung
• Format: Journal Article
• Language: English
• Published: New York IEEE 01.09.2005; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Amplifiers; analog driver; Bandwidth; CMOS analog integrated circuits; Crosstalk; Delay; Driver circuits; low-dropout regulator (LDO); Optimal control; Power transistors; Regulators; Sensors; slew rate; slew-rate enhancement (SRE) circuit; Transient response; transient responses; Voltage
• ISSN: 1549-7747; 1558-3791
• DOI: 10.1109/TCSII.2005.850781

Low-power analog driver based on a single-stage amplifier with an embedded current-detection slew-rate enhancement (SRE) circuit is presented. By developing a systematic way to design both the response time and optimal sizing of driving transistors in the SRE circuit, the SRE circuit can be controlled to turn on or turn off properly. In addition, the analog driver only dissipates low static power and its transient responses are significantly improved without transient overshoot when driving large capacitive loads. Implemented in a 0.6-/spl mu/m CMOS process, a current-mirror amplifier with the current-detection SRE circuit has achieved over 43 times improvement in both slew rate and 1% settling time when driving a 470-pF load capacitor. When the proposed analog driver is employed in a 50-mA CMOS low-dropout regulator (LDO), the resultant load transient response of the LDO has 2-fold improvement for the maximum load-current change, while the total quiescent current is only increased by less than 3%.