Rüdiger Kuhn

An 82μA/MHz microcontroller with embedded FeRAM for energy-harvesting applications

In recent years energy-harvesting technology has become much more mature. The energy source is free and widely available. However, there are some limitations that energy-harvesting devices need to cope with, to build a reliable system. First of all the peak current of typical energy-harvesting power sources is quite limited [1] and the systems active power must be as low as possible. A second limitation is the possibility of interruption or fluctuation of power source. For example, solar energy is only available during the day, and thermal or vibrational energy sources may change depending on environmental conditions. As a consequence, systems must retain state and information despite possible power outages. Flash or EEPROM as todays standard non-volatile memory is slow in write access and has high peak current demands due to the required charge pump for erase and write cycles. Flash technology has limited write endurance in the order of 105 write cycles requiring a Wear Leveling algorithm [2] for large cycle state storage. SRAM could be used for fast, low-power read/write [3], but it requires a separate battery for state retention.

A 92.1% efficient DC-DC converter for ultra-low power microcontrollers with fast wake-up

In this paper, we present a 92.1% peak efficiency DC-DC converter for integration in a ultra-low power micro-controller. The converter is designed to drastically reduce the wake-up energy of the system while achieving a high efficiency value of 92.1% and a small quiescent current of only 440 nA. The converter guarantees an output ripple smaller than 30 mV loaded with only 56 nF. The regulator is fabricated in a 130 nm CMOS process and occupies 0.14 mm2. It operates from 1.8 V to 3.3 V and provides a stable output of 1.2 V.

An ultra-low power, 2mA Iout buck converter optimized for <50mV ripple at a load cap of only 27nF

A novel, simple DC-DC concept for low-power applications is presented. We propose a predictive peak-current mode controller in discontinuous conduction mode (DCM). The design is able to operate with a minimized output capacitor of only 27nF. Measurements shows low ripple voltage even at maximum load current steps and excellent transient response at a good DC control of Vout.