KEYWORDS: Microcontrollers, System on a chip, Control systems, Resistors, Resistance, Manufacturing, Modulators, Sensors, Sensor networks, Integrated circuits
In the last few years the increased development of wireless technologies led to the development of micropower devices with power management and real time power control, aimed to maximize the battery life time.1 The main and simplest method to estimate residual battery life time is by voltage measurement. This kind of measurement is simple but is useless in many cases, especially when long term Lithium-Thionyl chloride batteries are used, since its voltage is flat for more than 90% of the battery discharge. In this case, a current control should be used. However, these kinds of devices have various problems as a limited range of measurement and not negligible quiescent current that may distort the measurements. In this work we developed a micropower supervisor for wireless sensor nodes with a charge battery monitor, whose features are aimed at solving the problems just described. The current measured by a sense resistor, is filtered by a super-capacitor, amplified by a current sense amplifier and then fed to a voltage to pulse frequency modulator. In this way, the charge consumption can be estimated without the saturation of the current sense amplifier, even if the wireless node consumes time limited high current spikes, for example during transmission.
KEYWORDS: Switching, Modulators, Modulation, Signal to noise ratio, Clocks, Quantization, Power supplies, Control systems, Systems modeling, Interference (communication)
A digital controller for high frequency Switching Power Supply based on Sigma Delta modulation is proposed in this work. A technique to restrict average switching frequency in a suitable range is used. The complete system has been modelled and simulated at system level using the SystemC-WMS environment. A high precision controller
has been designed with relatively low clock frequency and area occupancy of the Sigma Delta modulator, and at the same time reducing the sensitivity to parameter statistical variations and to temperature drift.
Dynamic Voltage Scaling is a technique that reduces supply voltage and clock frequency, depending on system
workload, with the aim of reducing power dissipation. This works is devoted to the modelling and integration in the
same system level simulation environment of the analog DC-DC converter for Dynamic Voltage Scaling, the Dynamic
Power Management and a test System on Chip with three Masters and two Slaves connected to the AMBA AHB bus.
The DC-DC converter is described with a detail such that it is possible to verify the effect of the transient during the
change of supply voltage on the performance of the DVS algorithm. SystemC and its extension SystemC-WMS have
been used as description languages in which a system level description of the dynamic supply management coexists
with the analog switching power converter and its control.
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