Differential common-gate techniques for high performance power management integrated circuits
by Yat Hei Lam
Ph.D. Electronic and Computer Engineering
xv, 114 leaves : ill. ; 30 cm
Portable applications often need multiple voltages controlled by a power management IC (PMIC) to power up various functional blocks. Dynamic performance in response to perturbations is important for a high performance PMIC, and could be enhanced by obtaining and making use of the current information besides the voltage information....[ Read more ]
Portable applications often need multiple voltages controlled by a power management IC (PMIC) to power up various functional blocks. Dynamic performance in response to perturbations is important for a high performance PMIC, and could be enhanced by obtaining and making use of the current information besides the voltage information.
Differential pairs with common‐source input stage are well known and arguably the most extensively employed circuit technique for voltage amplification. The infinite input impedance of the CMOS input stage is a notable advantage, but the limited common mode range, either at the supply rail or at ground, is the most restrictive aspect for low voltage applications. In contrast, differential amplifiers with a common‐gate input stage are seldom considered owing to their annoying finite input currents. However, for a unipolar supply voltage of VDD, a differential common‐gate (DCG) core circuit can handle I/O (input/output) with input common mode voltage of VDD or circuit ground that cannot be easily achieved by differential common-source circuits. Moreover, the DCG input stage is particularly suitable to manipulate current variables. Hence, DCG amplifiers would manifest their own importance in power management circuitries, where current information is as important as voltage information, and the demand for low power, compact and accurate on‐chip current sensing for control is mandatory.
In this research, novel differential common‐gate techniques are proposed and their peculiar features are studied. Accurate, compact and power‐efficient on‐chip current sensors are developed based on the DCG techniques, and they could be employed in five major power management components, namely, switch‐mode power converters, linear and low dropout regulators, voltage references, regulated charge pumps and RF (radio frequency) AC‐DC rectifiers.
On‐chip DCG current sensors are first employed in two buck‐boost converter designs with supply independent control schemes. Both converters operate in pseudo‐continuous conduction mode and exhibit excellent line perturbation rejection.
The current sensor is next employed in the design of a low dropout regulator with direct current feedback that eliminates the need of the output capacitor and gives excellent line and load regulations.
The DCG core of the on‐chip current sensor can be used in applications that require accurate current and voltage mirroring. A family of symmetrically matched current‐voltage mirrors (SM CVMs) is explored. A series of current efficient bandgap references designed with the SM CVM are developed.
The DCG techniques are further applied to design active diodes in two applications. The first application is a regulated voltage doubler (regulated charge pump) using active rectifiers to eliminate reversion loss. The second application is an integrated AC‐DC active rectifier for wirelessly powered devices in the radio frequency range of 13.56MHz. Reverse current control was proposed and the active rectifier achieved efficiency that matched with an ideal diode with zero forward drop. All circuits are designed in a 0.35μm CMOS process.