Abstract:
An integrated circuit having a housing in a control unit provides at least two voltage levels, has a watchdog for monitoring a processor, performs an evaluation of at least one acceleration signal to enable at least one ignition output stage, and has at least one first interface for connecting to at least one sensor situated outside the control unit.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to an integrated circuit having a housing in a control unit. 
         [0003]    2. Description of Related Art 
         [0004]    A control unit for activating passenger protection means, in which a processor is provided in and a security IC is provided parallel thereto, which monitors sensor values independently of the processor, is described in published German patent document DE 100 57 915. An ignition circuit component having ignition output stages for activating the ignition element is also provided. 
       A BRIEF SUMMARY OF THE INVENTION 
       [0005]    The integrated circuit according to the present invention, having a housing in a control unit, has the advantage over the related art that different functions are now situated in a single component within a housing. These functions include the power supply unit, a watchdog for monitoring the processor of the control unit, a function for independent monitoring of the sensor values to release the ignition output stages as a function thereof, and interfaces for connecting at least one sensor situated outside the control unit. This integrated component therefore represents a very compact, cost-effective, and reliable achievement of the object of integrating all of these functions into one component. Therefore, the electronics material costs and the required circuit board area are reduced. By reducing the required number of elements, a reduction of the overall breakdown rate of the control unit is also to be expected. 
         [0006]    It is particularly advantageous that the integrated circuit additionally has a further interface for communication with sensors or other control units. This interface may, for example, be implemented as a CAN bus interface or as a K line. 
         [0007]    In particular, it is advantageous that the watchdog is implemented in three stages. The three-stage watchdog performs system clock monitoring, monitors the correct sequence of system-relevant software-based functions, and monitors built-in self-tests of system components, such as memory components or other internal processor components. 
         [0008]    In addition, it is advantageous that the power supply unit additionally has the function of charging an energy reserve of the control unit which is required for the autonomous time. 
         [0009]    The power supply unit also has a DC voltage converter for an increased voltage for the energy reserve, a step-down converter for a 6.7 V power supply unit, and components for the 5 V and 3.3 V power supply unit. Linear voltage regulators may be used here. 
         [0010]    In addition, the integrated circuit according to the present invention advantageously has a reset manager. A reset is produced in the event of overvoltage or undervoltage or a watchdog error, and to reset the logic of the control unit processor, such as a microcontroller. 
         [0011]    Finally, it is also advantageous that the integrated circuit according to the present invention also contains the ignition output stages. Therefore, multiple elements may be provided using a single integrated circuit. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
         [0012]      FIG. 1  shows a block diagram of a control unit having the integrated circuit according to the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0013]    The electronic functions and functions implemented in software of a control unit for activating passenger protection means, such as airbags, belt tensioners, or pedestrian protection means, are becoming increasingly more intelligent. Different components are offered for this purpose. However, costs are an important factor in automobile electronics, so that a cost reduction is necessary here. 
         [0014]    Therefore, the following functions are assembled into a single integrated circuit according to the present invention: 
         [0015]    The power supply unit, a security function, and interfaces. In addition, the ignition output stages may also be integrated into the integrated circuit. The security function includes a watchdog for the processor located in the control unit, preferably a microcontroller, and an evaluation of the acceleration signals independently of the microcontroller. This refers to the security semiconductor known from the related art. The functions also include interfaces to the external sensors and also other communication interfaces, such as the K line or CAN. The unidirectional connections to the sensors are possible, such as a bus interface and the LIN interface. 
         [0016]      FIG. 1  shows a block diagram of the integrated circuit according to the present invention, which is situated in a control unit. The dashed boundary line indicates the control unit. Integrated circuit  100 , to which the cathode of a diode  102  is connected, is located inside the control unit. This connection of the cathode of diode  102  leads to a block  118  in circuit  100 , which is responsible for the power supply. This block  118  performs the following functions: it has a step-output or step-down converter for the energy reserve, it has a voltage converter to achieve 3.3 V from the existing 5 V, and it has a voltage regulator for this 3.3 V. 
         [0017]    In addition, block  118  has a reset function to restart the control unit in case of an error, for example. Block  118  is additionally connected to a regulator  101 , to which energy reserve  122  is connected as a capacitor in relation to ground. Regulator  101  ensures charging of energy reserve  122  and, in case of triggering, supplying the energy stored in the energy reserve  122  to a block  119 , which represents the ignition output stages. The ignition current is typically always obtained from energy reserve  122 . Alternatively, it is possible to provide ignition output stages  119  outside component  100 . However, block  119  is also supplied internally with energy from block  118  to operate the logic provided in block  119 , for example. 
         [0018]    An SPI (serial peripheral interface) bus  121 , which allows data communication, is provided internally between blocks  119  and  118 ,  123  and  120 . An SPI bus  105  is also connected to this SPI bus  121 , outside the component  100 . Not only a memory  104 , which is implemented here as an EEPROM, but also microcontroller  112  and sensors  107  through  110 , are connected to this bus  105 . Inside integrated circuit  100 , block  120  performs the security functions, which include the parallel analysis of the sensor signals from sensors  107  through  110 , this analysis occurring in parallel to that of microcontroller  112 , and the watchdog function, which monitors the function of microcontroller  112 . These functions are all executed via SPI buses  121  and  105 . In particular, the watchdog performs the system clock monitoring, the monitoring of the correct sequence of the system-relevant software-based functions, and the monitoring of built-in self-tests of system components, such as memory components  104 . The watchdog may thus be implemented as a three-fold watchdog, since it performs three functions in parallel here. Block  123  represents the interface functions of integrated circuit  100 . Block  123  is therefore connected via inputs/outputs  117  to the outside world of the control unit. In particular, block  123  is connected via a K line or LIN interface via input/output  116  to the outside world, for example, to weight sensors on a vehicle seat. Block  123  is connected via inputs/outputs  115  to externally connected acceleration sensors, which are located in the vehicle side and/or the vehicle front as front sensors, for example. Sensor signals of these external sensors are analyzed by the safety controller of block  120  in parallel to microcontroller  112  in order to establish whether it is actually a case for triggering. 
         [0019]    Microcontroller μC determines, on the basis of the sensor data of sensors  107  through  110  and the external sensors, which provide their data via inputs  115  and  114  to block  100 , whether the triggering of restraining means is necessary. Since microcontrollers such as microcontroller  112  may have malfunctions under certain circumstances and incorrect triggering may occur, it is necessary to provide redundant analysis, which is implemented by block  120 . This analysis by block  120  is less detailed than that which processor  112  performs itself. Data which is required for a post-crash analysis is stored in memory  104 , which is implemented as an EEPROM. This data includes, for example, error and operational characteristic values, such as the measured accelerations which have resulted in triggering, triggering times, times of day, etc. As shown in  FIG. 1 , block  107  is implemented as a roll rate sensor, while sensor  108  senses accelerations in the Y and Z directions. Y means a lateral direction of the vehicle and Z means a vertical direction of the vehicle. The X direction is detected by sensor  109 , for example, which detects accelerations in the vehicle longitudinal direction. An X-Y sensor  110  which detects accelerations in the vehicle longitudinal direction and vehicle transverse direction, respectively, is also provided. Angled arrangements of the acceleration sensors are possible, of course. Processor  112  is connected via an interface component  113  via the K line to other control units, for example. K line is an established concept and stands for communication line. Processor  112  is connected to two drivers  111  via an output. Drivers  111  are configured as low side switches, for example, for turning on and off a lamp and producing a digital signal, as a pull-up in the receiver of the signal. 
         [0020]    An example operation of the control unit having component  100  according to the present invention is as follows. Energy reserve capacitor  122  is charged by using component  100  via diode  102  and block  118 . In addition, block  118  provides the operating voltages for the control unit. These operating voltages include 5 V and also 3.3 V, which are provided in regulated form. The control unit receives sensor values from sensors  107  through  110  and the external sensors via inputs  114  and  115  in order to determine whether a crash condition exists. The sensor values are analyzed by processor  112 . The acceleration signals are typically smoothed or integrated and compared to variable or fixed thresholds. In parallel to this, block  120  also uses a safety controller to monitor these sensor values via fixed thresholds, for example, to determine whether a case for triggering may actually occur. This redundancy ensures that malfunctions of microcontroller  112  are recognized. Such malfunctions are also continuously monitored by a watchdog functionality of block  120 , however. In addition to the system clock monitoring, these watchdog functions also include the monitoring of the software-based functions of microcontroller  112 , in that specific questions are put to the microcontroller to establish, on the basis of the results whether the microcontroller is still capable of correctly answering these questions. A further function of the watchdog is the monitoring of built-in self-tests of system components, such as memory components or other internal processor components. Block  123  thus ensures the supply of external sensor data, but other external data may also be detected via inputs/outputs  117 . 
         [0021]    If a case for triggering is established by microcontroller  112  and verified by block  120 , output stages  119  are enabled by block  120  and the fire command is transmitted from processor  112  via SPI line  105  and  121  to output stages  119 , so that these are then enabled. This causes the energy which is stored in energy reserve  122  to be supplied via block  101  to the output stages, which supply the energy to ignition elements  106 , so that the ignition elements are fired, and in turn the restraining means are triggered. 
         [0022]    In addition to the components shown here, further components may be situated in the control unit.