Hanh-Phuc Le

Design Techniques for Fully Integrated Switched-Capacitor DC-DC Converters

This paper describes design techniques to maximize the efficiency and power density of fully integrated switched-capacitor (SC) DC-DC converters. Circuit design methods are proposed to enable simplified gate drivers while supporting multiple topologies (and hence output voltages). These methods are verified by a proof-of-concept converter prototype implemented in 0.374 mm2 of a 32 nm SOI process. The 32-phase interleaved converter can be configured into three topologies to support output voltages of 0.5 V-1.2 V from a 2 V input supply, and achieves 79.76% efficiency at an output power density of 0.86 W/mm2 .

A Single-Inductor Switching DC–DC Converter With Five Outputs and Ordered Power-Distributive Control

An integrated 5-output single-inductor multiple-output DC-DC converter with ordered power-distributive control in a 0.5mum BiCMOS process is presented. The converter has four main positive boost outputs programmable from +5 to +12V and one dependent negative output from -12 to -5V. A maximum efficiency of 80.8% is achieved at a total output power of 450mW, with a switching frequency of 700kHz.

A 32nm fully integrated reconfigurable switched-capacitor DC-DC converter delivering 0.55W/mm 2 at 81% efficiency

With the rising integration levels used to increase digital processing performance, there is a clear need for multiple independent on-chip supplies in order to support per-IP or block power management. Simply adding multiple off-chip DCDC converters is not only difficult due to supply impedance concerns, but also adds cost to the platform by increasing motherboard size and package complexity. There is therefore a strong motivation to integrate voltage conversion blocks on the silicon chip.

The Road to Fully Integrated DC–DC Conversion via the Switched-Capacitor Approach

This paper provides a perspective on progress toward realization of efficient, fully integrated dc-dc conversion and regulation functionality in CMOS platforms. In providing a comparative assessment between the inductor-based and switched-capacitor approaches, the presentation reviews the salient features in effectiveness in utilization of switch technology and in use and implementation of passives. The analytical conclusions point toward the strong advantages of the switched-capacitor (SC) approach with respect to both switch utilization and much higher energy densities of capacitors versus inductors. The analysis is substantiated with a review of recently developed and published integrated dc-dc converters of both the inductor-based and SC types.

A Minimally Invasive 64-Channel Wireless μECoG Implant

Emerging applications in brain-machine interface systems require high-resolution, chronic multisite cortical recordings, which cannot be obtained with existing technologies due to high power consumption, high invasiveness, or inability to transmit data wirelessly. In this paper, we describe a microsystem based on electrocorticography (ECoG) that overcomes these difficulties, enabling chronic recording and wireless transmission of neural signals from the surface of the cerebral cortex. The device is comprised of a highly flexible, high-density, polymer-based 64-channel electrode array and a flexible antenna, bonded to 2.4 mm × 2.4 mm CMOS integrated circuit (IC) that performs 64-channel acquisition, wireless power and data transmission. The IC digitizes the signal from each electrode at 1 kS/s with 1.2 μV input referred noise, and transmits the serialized data using a 1 Mb/s backscattering modulator. A dual-mode power-receiving rectifier reduces data-dependent supply ripple, enabling the integration of small decoupling capacitors on chip and eliminating the need for external components. Design techniques in the wireless and baseband circuits result in over 16× reduction in die area with a simultaneous 3× improvement in power efficiency over the state of the art. The IC consumes 225 μW and can be powered by an external reader transmitting 12 mW at 300 MHz, which is over 3× lower than IEEE and FCC regulations.

A Single-Inductor Step-Up DC-DC Switching Converter with Bipolar Outputs for Active Matrix OLED Mobile Display Panels

A single-chip dual-output step-up DC-DC converter is implemented for active-matrix OLED mobile display panels. The bipolar outputs are regulated independently and integrated with a boost and a charge-pump topology sharing a single inductor. The chip is 4.1mm2 fabricated in a 0.5 mum power BiCMOS process and operates at 1MHz with a maximum efficiency of 82.3% at an output power of 330mW.

A comparative analysis of Switched-Capacitor and inductor-based DC-DC conversion technologies

This paper compares the performance of Switched-Capacitor (SC) and inductor-based DC-DC conversion technologies. A metric to compare between the two topologies is discussed, and is used to compare switch utilization. Fundamental limits on utilization of reactive elements developed in the literature for all DC-DC converters are also reviewed and discussed, and this analysis shows that popular SC and inductor-based converters achieve the limits of utilization for reactive components. These limits are stated in terms of the ratio of output power to required stored energy in reactive elements. A detailed analysis of available surface mount discrete components and on-die devices reveals that capacitors have substantially higher energy and power density than their magnetic counterparts. The challenging regulation task for SC converters is also discussed, with a promising strategy outlined. The SC converter is evidently a promising candidate for future high power density integrated DC-DC converters.

A Single-Inductor Step-Up DC-DC Switching Converter With Bipolar Outputs for Active Matrix OLED Mobile Display Panels

A single-inductor step-up DC-DC switching converter with bipolar outputs is implemented for active-matrix OLED mobile display panels. The positive output voltage is regulated by a boost operation with a modified comparator control (MCC), and the negative output voltage is regulated by a charge-pump operation with a proportional-integral (PI) control. The proposed adaptive current-sensing technique successfully supports the implementation of the proposed converter topology and enables the converter to work in both discontinuous-conduction mode (DCM) and continuous-conduction mode (CCM). In addition, with the MCC method, the converter can guarantee a positive output voltage that has both a fast transient response of the comparator control and a small output voltage ripple of the PWM control. A 4.1 mm2 converter IC fabricated in a 0.5 mum power BiCMOS process operates at a switching frequency of 1 MHz with a maximum efficiency of 82.3% at an output power of 330 mW.

A 2W CMOS Hybrid Switching Amplitude Modulator for EDGE Polar Transmitters

An amplitude modulator for class-E2 EDGE polar transmitters is fabricated in a 0.35mum CMOS process. This hybrid switching modulator consists of a class-D amplifier with a 2MHz switching frequency and a wideband buffered analog amplifier having low output impedance of 200mOmega at high frequency. It can drive an RF PA with an equivalent impedance of 4Omega up to maximum output power of 2.25W with a maximum efficiency of 88.3%. The chip area is 4.7mm2.

Load-Independent Control of Switching DC-DC Converters with Freewheeling Current Feedback

In this paper, a load-independent converter with freewheeling current feedback, whose output is controlled by a comparator, is presented. This control method is very useful for single-inductor multiple-output (SIMO) converters. A single-inductor bipolar-output (SIBO) converter with the proposed control scheme is implemented in a 0.5 mum power BiCMOS process and uses 3.2 mm2 of die area. The current sensing gain can be increased and and the circuit is less sensitive to switching noise than CPM converters are because the slope compensation used in CPM converters reduces the current sensing gain to comply with low supply voltage.