Abstract:
Disclosed is an integrated electronic circuit comprising a core circuit that generates a useful signal as well as a buffer for storing the useful signal. The buffer stores the last read value of the useful signal for a predetermined period of time when the power supply is interrupted, and the buffer is disconnected from the power supply of the other circuits.

Description:
PRIORITY INFORMATION 
       [0001]    This patent application claims priority from PCT Application No. PCT/EP2006/010811 filed Nov. 10, 2006, German Application No. 10 2005 054 257.3 filed Nov. 11, 2005 and German Application No. 10 2006 022 221.1 filed Jan. 16, 2006, which are hereby incorporated by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    The invention relates to an integrated electronic circuit, and in particular to an integrated circuit comprising a core circuit generating a measured signal. 
         [0003]    A measured signal generated by a core circuit may be further processed in other circuits within an integrated circuit or it may be output. A disturbance in the power supply, e.g. a voltage breakdown, an interruption or an overvoltage may have an undesired effect on the measured signal. Thus the further processing or the output of the signal is impaired. It is an aim of the invention to ensure the processability of the measured signal. 
       SUMMARY OF THE INVENTION 
       [0004]    The invention provides an integrated electronic circuit, wherein the effects on the measured signal from a disturbance in the power supply to the integrated circuit are minimized. During normal operation, i.e. without any disturbance in the power supply, the measured signal can continuously be stored in an intermediate memory and can be provided from there to the other circuits within the integrated circuit. If a disturbance occurs, which has an effect in particular to the measured signal, then, rather than using the disturbed measured signal, the latest value of the measured signal stored in the intermediate memory may be used as a fallback. Due to the decoupling from the power supply of the other circuits, the intermediate memory is not affected by the disturbance and is capable to preserve the value which was written-in before the disturbance, during the period of disturbance. Without this decoupling, an arbitrary value would manifest in the intermediate memory, which may lead to unpredictable results during further processing of the measured signal. The provision of the latest read-in value of the measured signal in the intermediate memory ensures a measured signal with minimal leaps, thus facilitating further processing in other circuits of the integrated circuit or in external circuits which are provided with the measured signal. 
         [0005]    According to an advantageous embodiment of the invention, the intermediate memory stores the latest read-in value at least until it is ensured that valid values are again read-in to the intermediate memory. Depending on its design, the core circuit may not be able to output valid values directly after a disturbance of the power supply. For example, if the core circuit undergoes a reset procedure after the disturbance. In this case, it may take some time until the core circuit will again provide a reasonable measured signal. During this time, the core circuit outputs for example a signal whose value may be close to zero voltage or close to the supply voltage. By means of the invention, this period is bridged by the intermediate memory providing the latest read-in value of the measured signal. 
         [0006]    According to an advantageous embodiment of the invention, it is provided that the integrated electronic circuit forms an active sensor, in which the core circuit is a measuring circuit, generating a measuring signal as measured signal. Such a sensor provides a high reliability, because the effects of disturbances in the power supply are minimized. In particular, such a sensor may provide a defined output signal immediately after disturbances in the power supply. The high reliability is of particular importance with the use of sensors in automotive, where sensors may be exposed to numerous disturbances, e.g. by the ignition. 
         [0007]    According to another advantageous embodiment of the invention, it is provided that the sensor is a distance or an angular sensor. The active distance or angular sensor according to aspects of the invention may replace electro-mechanical distance or an angular sensors, e.g. potentiometers, and offers the advantage of a longer lifetime, higher reliability and lesser sensibility to soiling, without having to trade in these advantages with a, with regard to electro-mechanical sensors, higher sensibility to disturbances in power supply. 
         [0008]    These and other objects, features and advantages of the present invention will become more apparent in light of the following detailed description of preferred embodiments thereof, as illustrated in the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         [0009]    The sole FIGURE is a block diagram illustration of an integrated circuit. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0010]    The embodiment comprises an integrated circuit  10 , forming an active distance or angular sensor, with a measurement circuit  12 , an intermediate memory  16  and an output circuit  18 . The integrated circuit  10  further comprises a power supply  20  and a control unit  22 . The integrated circuit may also comprise further units which are not relevant for comprehending the invention. 
         [0011]    The measuring circuit  12  generates a measuring signal on a line  14 , which corresponds to a measured distance or angle. The measuring signal on the line  14  is stored in the intermediate memory  16  and is available for the output circuit  18 . The latter may read-out the measuring signal, process it further if applicable, and provide an output signal on a line  15  in response to the measuring signal. 
         [0012]    The power supply  20  provides the needed energy for the measuring circuit  12 , the control circuit  22  and the output circuit  18 . The intermediate memory  16  is connected to the power supply  20  via a decoupling device  24  and is buffered by an integrated storage element  26 , thus, the intermediate memory  16  is decoupled from disturbances in the power supply. By the integrated storage element  26 , advantageously external components such as capacitors for buffering are rendered obsolete. Decoupling may in particular be designed to avoid impairment of the intermediate memory upon a reversal of the supply voltage caused by disturbance, i.e. when a momentary negative supply voltage Vdd occurs. 
         [0013]    The control circuit  22  monitors the power supply and controls the intermediate memory  16 . As long as the power supply is ok, i.e. the supply voltage V dd  is within a range where the connected circuits work properly, especially the measuring circuit  12  provides a reasonable measuring signal, the control unit  22  controls the intermediate memory in such a way that it reads-in the measuring signal an provides it to the output circuit. 
         [0014]    A disturbance in the power supply, e.g. by a break-in of the supply voltage, causes the intermediate memory to cease reading-in the measuring signal. In the simplest case, this is induced by failure of the control unit  22  which results in missing control for the intermediate memory. Since the intermediate memory  16  has its own power supply, it is not affected by the disturbance, and therefore no senseless, e.g. arbitrary values may reach the intermediate memory, but the latest read-in value is conserved. 
         [0015]    The control unit  22  provides for that, after the disturbance, when the power supply is restored, the value that has been stored in the intermediate memory  16  before the disturbance, is available for a determined period, so the output circuit  18  may be able to provide an output signal with a defined value even immediately after the disturbance. If the disturbance has a short duration with regard to the variation velocity of the measuring signal, then the output signal can append without great error to the signal form before the disturbance. Thus, the output signal experiences only an indispensable error caused by the disturbance in the power supply. A longer-term deviation in the measuring signal, which may be caused by the measuring circuit  12  having a malfunction due to the disturbance of the power supply can thereby be bridged. 
         [0016]    In one embodiment of the invention, the integrated circuit  10  is reset after each disturbance. During this time, the measuring circuit  12  does not provide the desired measuring signal, rather the measuring signal takes a defined, but undesired value, e.g. the maximum or minimum possible value, the measuring circuit is able to provide. In this case, the above-mentioned period of availability of the value, which was stored in the intermediate memory  16  before the disturbance, is at least so long that it includes the period of reset. 
         [0017]    In this case too, the value stored before the disturbance will mostly append better to the measuring signal delivered after reset than a maximum or minimum value delivered by the measuring circuit during reset. Hence, all together an output signal with minimal leaps results, which importantly facilitates further processing in the subsequent circuits. 
         [0018]    The integrated circuit  10  may be, for example, a hall-sensor, where the measuring circuit  12  comprises the original sensor circuit and transfers the measuring values from the sensor into the measuring signal on the line  14 . The invention ensures that the sensor provides a defined measuring value, i.e. the one assessed just before the disturbance, for a determined period of time. Hence, the sensor provides a measuring signal with minimal steps. 
         [0019]    The invention is applicable to sensors with analog or digital signal processing, regardless which segments of the signal path are analog and which are digital. 
         [0020]    Although the present invention has been illustrated and described with respect to several preferred embodiments thereof, various changes, omissions and additions to the form and detail thereof, may be made therein, without departing from the spirit and scope of the invention.