• Author: Guadalupi Arturo
  • Description:

    The main scope of this thesis is to prepare the base for the use and the radiation charac-
    terization of the new Texas Instruments’ FRAM micro-controllers within the Modular
    Architecture for Satellites (AraMIS) developed by the Politecnico di Torino. These kind
    of micro-controllers seem to be very appealing for space applications based on Commer-
    cial O The Shelf (COTS) components because of their intrinsically radiation hardened
    structure and their low power consumption compared with standard FLASH based one.
    The idea of using ferroelectric materials to store digital can be dated back to 1952, but
    it was practically implemented only starting from the 80s because the needed advanced
    technology to develop them wasn’t available before. FRAM based micro-controllers are
    instead available on the market since about one year and an half. The ferroelectric RAM
    memory, known as FeRAMF or FRAM, is conceptually similar to the DRAM cell, but
    there is an important di erence that lies in the dielectric of the storage capacitor: while
    DRAM cells use a layer of standard linear material, the dielectric of a FeRAM cell is
    made of ferroelectric material, usually lead (Pb) Zirconate Titanate (PZT).
    Using a ferroelectric dielectric leads to a di erent behavior of the cell compared
    with a DRAM one, leading to many advantages especially for what concern the overall
    power consumption in read/write cycles. Furthermore, the material exhibits two stable
    polarization conditions and it’s possible to switch between them by means of an electric
    eld with opposite polarity. Since the polarization will be kept after the applied eld
    is removed, it is possible to link the polarization state to a logic state and so these
    materials can be used to build a non volatile memory device. No periodic refresh is so
    necessary to keep the information, like in a DRAM memory.
    The reading process is destructive: it is not possible to read the content of a cell
    without actually clearing it, because of the way the information is stored in the device.
    To know which of the possible polarization states the dielectric holds, the only way is to
    write a new value to the cell with the bit-line pre-charged but in high impedance state
    and depending on the previous polarization, this process will or won’t produce a voltage
    pulse out of the bit-line. Read and write cycles require basically the same operations
    and can both be completed in times in the order of tens of nanoseconds and without
    using high voltage charge pump like in FLASH memories.
    The three main design parameters of the electronic systems of small satellites are:
     power consumption;
     physical dimensions;
     radiation environment behavior.
    The electric power in the satellite comes from solar panels, which are necessarily of
    small dimensions because of the mechanical structure, leading to few Watt of average
    power to cover all the needed functions. It is so necessary to make the best use of any
    mW of available power. Furthermore launch costs are directly proportional to the mass
    of the system, so it is absolutely necessary to reduce as much as possible dimensions
    and mass of the electronic system. We said that FeRAM memories are RAM devices,
    meaning that read and write procedures do not di er signi cantly and random write is
    possible without the need of a previous erase of a cell, but they are also non volatile,
    we can so for sure state that this leads to save power. In fact in DRAM devices most of
    the power is used by the refresh procedure otherwise the stored informations are lost.
    Furthermore the refresh process leads to a decreasing in the overall speed performances.
    At the moment there are no big FRAM memory available on the market, but in any
    case, memory requirements of small satellites are normally compatible with the size of
    available FeRAM, except for imaging payloads if local storage of a certain number of
    images is mandatory.
    Because the FRAM cell stores the state as a PZT lm polarization, an alpha hit
    have a very small possibility to cause a change in the polarization. FRAM terrestrial
    Soft Error Rate (SER) is not even measurable. This “radiation resistant” characteristic
    of FRAM makes it attractive for use in several medical applications and space one.
    Arturo Guadalupi iv
    Keeping in mind the concepts exposed above, this work is focused on the development
    of a payload tile for the AraMIS structure called 1B521 Radiation Characterization
    Payload whose aim is to introduce the usage of new FRAM micro-controllers within
    the AraMIS nano-satellite structure and characterize them for low cost space applica-
    tions in therms of radiations. In particular it is requested to characterize the use of
    a FRAM micro-controller (MSP430FR6989) in therms of Total Ionizing Dose (TID),
    Single Event E ect (SEE), like Single Event Upset (SEU) and Single Event Latch-up
    (SEL), power eciency and reliability in general. No scienti c data coming from real
    space experiments or terrestrial simulations (using for example particles accelerators)
    are available at the moment. It is furthermore requested to show the eciency of the
    AraMIS’ developed software hardening library in order to have a direct comparison be-
    tween a standard compiled code and an hardened one.
    The AraMIS radiation-hardening technique, is based on the use of appropriate C++
    classes from the hardened data (Hdata) package developed in house, which can be used
    in a common C++ program instead of standard data type. For instance, a short can be
    substituted by the so-called TripleShort, which automatically and transparently stores
    three copies of the same value and votes or recovers data whenever required. A normal
    C++ program can so still be compiled by modifying only the data type de nitions.
    This makes possible to reuse software algorithms and procedures which have already
    been validated and tested without any speci c e ort apart from rede ning data types
    drastically reducing the development time.
    This thesis has to be considered an user guide manual about the developed payload
    tile, and a base for future developments on FRAM microcontrollers within the AraMIS
    nano-satellite structure. The rst part of the developed work in-fact makes possible
    to introduce and start using any kind of FRAM micro-controllers that belongs to the
    family MSP430FRxxxx without an heavy e ort. All the hardware-dependent choice
    that have been made are explained and the software commented in order to be easily
    understandable and useful for feature developments.
    Arturo Guadalupi v
    Here a little overview about the structure of the thesis.
    Chapter 1 gives an introduction about the space radiation environments, its interaction
    with the electronics and the used shielding techniques.
    Chapter 2 gives an overview about the FRAM technology and some concept about
    their pro and cons about their use in space applications.
    Chapter 3 and Chapter 4 give an overview about the UML approach in the AraMIS
    structure and how it is organized.
    Chapter 5 explain the design of the developed PCB and what hardware has been chosen
    in order to give support to the developed software.
    Chapter 6 shows the software structures behind the designed tile, how to it commu-
    nicates with the OBC and the type of tests that are executed.
    Chapter 7 gives an overview about the tests that has been made to validate the work
    and the reached results. What can be done in the feature to improve the what have
    been done is also mentioned.

  • Year: 2015
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