Abstract:
A power component is proposed which reliably switches inductive loads and has a current detection element to detect the current through the inductive load. The component includes a protective element which is connected to the source terminals of the sense element and of the actuator. The protective element protects against parasitic effects between the sense element and the actuator.

Description:
FIELD OF THE INVENTION 
     The present invention relates to a power component. 
     BACKGROUND INFORMATION 
     Power components having an actuator which is adjacent to a measuring element are already known in the form of SENSEFET transistors. 
     SUMMARY OF THE INVENTION 
     In contrast, the power component of the present invention has the advantage that it ensures safe and reliable operation even with high currents through the actuator as well as protection against the risk of failure. 
     In SmartPower components such as SENSEFET transistors in particular (in DMOS design, for example) or in IGBT transistors having an integrated sense element, a reliable protection is ensured against overvoltange and breakdowns between the sense cell and adjacent DMOS cell. In particular when employed as a high-side switch, critical operating conditions such as, for example ground and/or battery separation, ISO pulses (interference pulses from the supply system) or with inductive loads or cable inductances can be withstood without risk of failure of the power component. Moreover, it has proven to be advantageous that there is no adverse effect on the current detection by the sense element in normal operation as a consequence of the arrangement provided. Moreover, the arrangement can be integrated monolithically. 
     If the arrangement prevents an activation of existing parasitic bipolar transistors, for example, by preventing the buildup of the base potential, then the danger of a second breakdown with subsequent fusing is prevented. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows a SENSEFET transistor in cross-section. 
     FIG. 2 shows a first exemplary embodiment. 
     FIG. 3 shows a second exemplary embodiment. 
     FIG. 4 shows a third exemplary embodiment. 
     FIG. 5 a  shows a fourth exemplary embodiment. 
     FIG. 5 b  shows a fifth exemplary embodiment. 
    
    
     DETAILED DESCRIPTION 
     FIG. 1 shows a transistor having a sense element, in cross-section. A weakly n-doped semiconductor layer is arranged on a p-doped substrate  1 . Weakly p-doped regions  3  are arranged in semiconductor layer  2 , the p-doped regions being separated from each other by regions of semiconductor layer  2 . A strongly p-doped region  4  is arranged in the center of each of regions  3 , the p-doped region extending from the surface of the semiconductor component to a depth in which region  4  is always directly in contact with semiconductor layer  2 . Strongly n-doped regions  5  are incorporated in the margins of strongly p-doped regions  4 , each of strongly n-doped regions  5  extending somewhat into weakly p-doped region  3  at the edge of each of the strongly p-doped regions  4 . A weakly p-doped region  30  is  25  also incorporated in semiconductor layer  2  by analogy to region  5 . By analogy to region  4 , a strongly p-doped region  40  is incorporated in weakly p-doped region  30 ; by analogy to strongly n-doped regions  5 , strongly n-doped region  29  is incorporated in strongly p-doped region  40 . Gate electrodes  6 , insulated from the semiconductor layer by an insulating layer, are arranged above the regions of semiconductor layer  2  which extend to the surface of the semiconductor component. Gate electrodes  6  are electrically connected with each other and can be electrically contacted via gate terminal  11 . Strongly n-doped regions  5  and strongly p-doped regions  4  are electrically connected with each other and can be jointly electrically contacted via source/load terminal  10 . Regions  40  and  29  are also electrically connected and can be electrically contacted via sense terminal  12 . Oxide layers and necessary metallic coatings on the surface of the semiconductor component are not shown in FIG. 1 for reasons of simplicity of presentation. If the component of FIG. 1 is designed as a DMOS power transistor, a strongly n-doped drain region, for example, is incorporated in weakly n-doped semiconductor layer  2 . This drain region is not shown in FIG.  1 . This drain region can be electrically contacted via a front drain terminal which is also not illustrated and in addition to load terminal  10 , gate terminal  11  and sense terminal  12 , represents the fourth terminal of a SENSEFET transistor. 
     The p-region  3 , p-region  30  and the region of semiconductor layer  2  lying between the two p-regions form a parasitic PMOS transistor. At a gate potential which is lower than the potential at sense terminal  12 , this parasitic PMOS transistor has a threshold voltage between source terminal  10  and sense terminal  12  which is, for example, 4 volts. If region  30  which represents the source region of the PMOS transistor is then in contact with a potential which is at least 4 volts higher than the potential of the p-region, a parasitic p channel is activated in semiconductor layer  2 . The parasitic PMOS transistor shifts current into region  3  of the adjacent DMOS cell which functions simultaneously as the base of a vertical npn bipolar transistor. This parasitic npn transistor is formed by regions  5 ,  3 / 4  and semiconductor layer  2 . In normal operating conditions, switching through this parasitic npn bipolar transistor by a short-circuit between the strongly n-doped region  5  and strongly p-doped region  4  is effectively prevented. The current of the parasitic PMOS transistor, however, allows the potential to build up in the base region of the parasitic bipolar transistor so that the npn bipolar transistor is activated and there exists the danger of a second breakdown with fusion. 
     FIG. 2 shows a SENSEFET transistor  41 ,  42 , a sense element  41  and an actuator  42  which, for example, is also constructed using DMOS technology. The gate electrodes of sense element  41  and actuator  42  are connected with a control circuit  47  which in turn is connected to the power supply via both ground terminal  45  and voltage source  46 . 
     Voltage source  46  is also connected to the drain terminals of the sense element and actuator. An analysis circuit  49  is connected between ground  45  and the source terminal of sense element  41 . An inductive load  50  is connected between source terminal  10  of actuator  42  and ground  45 . A protective diode  48  is connected between source terminal  10  of actuator  42  and the source terminal of sense element  41 , the negative pole of the protective diode being connected to source terminal  10  of actuator  42 . 
     (Externally controllable) control circuit  47  controls the current through actuator  42 . Analysis circuit  49  evaluates the current through sense element  41  which functions as a current detection element. Depending on the application, analysis circuit  49  is connected to other electronic circuits or to control circuit  47  in order to make the information concerning the size of the load current through actuator  42  available to the other circuit components and to control circuit  47 . If a ground separation or a voltage source separation occurs at inductive load  50 , the potential of source terminal  10  becomes negative due to the magnetic induction. As a result, protective diode  48  becomes conductive which guarantees that the source terminal of sense element  41  has a potential which is only a forward voltage higher than the potential of source terminal  10 . This effectively prevents the parasitic PMOS transistor from being activated. In normal operation, however, the diode does not influence the function of sense element  41  since in normal operation, protective element  48  is switched in reverse direction. 
     FIG. 3 shows an additional exemplary embodiment in which the same components are identified with the same reference symbols as in FIG.  2  and are not described again. 
     Instead of protective diode  48  in FIG. 2, a PMOS transistor  480  is connected to the source terminals of sense element  41  and actuator  42 , the transistor being connected as a diode in such a way that with negative potential of source terminal  10  of actuator  42 , the PMOS transistor is switched through. 
     FIG. 4 shows an additional exemplary embodiment in which a suppressor circuit  490  is arranged instead of protective element  48 . This suppressor circuit  490  has an NMOS transistor  62 , a first resistor  63  and a second resistor  64 . First resistor  63  is connected to the source terminal of actuator  42 . First resistor  63  is also connected with second resistor  64 . Second resistor  64  is connected to ground  45 . The first and second resistors are connected to the gate electrode of NMOS transistor  62 . The source terminal of transistor  62  is connected to source terminal  20  of actuator  42 . The drain terminal of transistor  62  is connected to the source terminal of sense element  41 . 
     NMOS transistor  62  switches through if actuator  42  has a negative source potential. The amount of the negative potential at which NMOS transistor  62  switches through can be adjusted via the resistance values of first resistor  63  and second resistor  64 . 
     FIG. 5 a  shows a cross-section of a component according to FIG. 1 with an integrated protective diode  48 . The same reference symbols as in FIG. 1 are not described here once more. Protective diode  48  has a weakly p-doped region  72  incorporated in semiconductor layer  2 , a strongly p-doped region  71  being incorporated in turn in p-doped region  72  which surrounds p-doped region  71 . A strongly n-doped region  70  is in turn incorporated in strongly  10  p-doped region  71 . Strongly n-doped region  70  is electrically connected to source terminal  10 ; strongly p-doped region  71  is connected to sense terminal  12 . Similar to FIG. 1, electrical insulating layers and metal coatings have been left out of the drawing for simplification of presentation. This also explains, for example, the stage of the right-hand one of the three gate electrodes  6  shown which is underlaid with an insulating layer. FIG. 5 b  shows a power component according to FIG. 1 with a protective element  480  designed as a PMOS transistor. Protective element  480 , which is arranged in the vicinity of the sense element, has two weakly p-doped regions  76  and  79  incorporated in semiconductor layer  2 , strongly p-doped regions  77  and  79  being incorporated in turn in weakly p-doped regions  76  and  78 , the strongly p-doped regions completely penetrating p-doped regions  76  and  78  and being in direct contact with semiconductor layer  2 . Gate electrode  75  of protective element  480  is connected to source terminal  10 ; strongly p-doped region  77  is connected to sense terminal  12  and strongly p-doped region  79  is, like gate electrode  75 , connected to source terminal  10 . 
     FIGS. 5 a  and b show simple implementations of the circuits according to FIGS. 2 and 3, respectively. No additional expense is necessary to implement protective elements  48  and  480  since regions  71 ,  72 ,  76 ,  77 ,  78  and  79  can be produced together with the semiconductor regions necessary for the actuator and the sense element. Of course, protective elements  48  and  480  can also be used in back-contacted components, i.e., vertical power components or even IGBT components.