Output Driver Equipped with a Sensing Resistor for Measuring the Current in the Output Driver

Abstract

An electronic circuit has an output driver for providing a driving signal. The output driver has a transistor with a first main terminal, a second main terminal and a control terminal coupled to receive a control signal, a power supply terminal, an output terminal for providing the driving signal that is coupled to the second main terminal, and a sensing resistor coupled between the power supply terminal and the first main terminal. The output driver further has means for temporarily disabling the coupling between the control terminal and the control signal during a peak voltage across the sensing resistor. The means may have a circuit that has a unidirectional current behavior, such as a diode, in series with the control terminal of the transistor.

1 . An electronic circuit comprising an output driver for providing a driving signal, the output driver including:
 at least two transistors, each transistor having a first main electrode, a second main electrode and a control electrode, the second main electrode of each of the at least two transistors being coupled together, and the control electrode of one of the transistors being coupled to receive a control signal;   a supply terminal;   an output terminal to provide the driving signal, the output terminal coupled to the second main electrode;   a sensing resistor coupled between the supply terminal and the first main electrode of the one transistor; and   means for rendering ineffective said coupling between the control electrode and the control signal during a peak voltage across the sensing resistor, said means being a unipolar circuit arranged in series with the control electrode of the one transistor.   
   
   
       2 . The electronic circuit of  claim 1 , wherein the unipolar circuit comprises a diode. 
   
   
       3 . The electronic circuit of  claim 1 , wherein the output driver further includes current means coupled between a further supply terminal and the control electrode of the one transistor. 
   
   
       4 . An electronic circuit as claimed in  claim 1 , wherein the output driver further includes limiting means for limiting the voltage on the control electrode of the one transistor. 
   
   
       5 . The electronic circuit of  claim 1 , wherein the output driver further includes limiting means for limiting the voltage between the control electrode and the first main electrode of the one transistor. 
   
   
       6 . The electronic circuit of  claim 4 , wherein the limiting means comprise a zener diode. 
   
   
       7 . The electronic circuit of  claim 1 , wherein the control signal is a binary signal. 
   
   
       8 . The electronic circuit of  claim 7 , wherein the output driver further includes a control circuit to supply the control signal, the control circuit including an inverter having an N-type field effect transistor and a P-type field effect transistor, the unipolar circuit being arranged in series with a drain of the P-type field effect transistor. 
   
   
       9 . The electronic circuit of  claim 8 , wherein the output driver further includes a further control circuit to supply a further control signal to the control electrode of the other one of the transistors. 
   
   
       10 . The electronic circuit of  claim 1 , wherein the output driver further includes a control circuit to supply a further control signal to the control electrode of the other one of the transistors. 
   
   
       11 . An electronic circuit comprising an output driver for providing a driving signal, the output driver including:
 a supply terminal;   a control circuit coupled to the supply terminal and configured and arranged to apply a voltage to a transistor control electrode;   at least two transistors, each transistor having a first main electrode, a second main electrode and a control electrode, the second main electrode of each of the transistors being coupled together, the control electrode of one of the transistors being coupled to receive a control signal from the control circuit, and the first main electrode of said one transistor being coupled to the supply terminal;   a sensing resistor coupled between the supply terminal and the first main electrode of said one transistor; and   an output terminal to provide the driving signal, the output terminal coupled to the second main electrode;   a unipolar circuit between the control circuit and the control electrode of said one transistor to decouple the control electrode from the control circuit during a peak voltage condition across the sensing resistor, wherein the supply terminal is coupled to the control circuit during the peak voltage condition.   
   
   
       12 . The electronic circuit of  claim 11 , wherein the control signal is a binary signal. 
   
   
       13 . The electronic circuit of  claim 12 , wherein the control circuit includes an inverter having an N-type field effect transistor and a P-type field effect transistor, the unipolar circuit arranged in series with a drain of the P-type field effect transistor. 
   
   
       14 . The electronic circuit of  claim 13 , wherein the output driver further includes a further control circuit coupled to the control electrode of the other one of the transistors and configured to supply a further control signal to the control electrode of the other transistor. 
   
   
       15 . The electronic circuit of  claim 11 , wherein the unipolar circuit is a diode. 
   
   
       16 . The electronic circuit of  claim 11 , wherein the output driver further includes a further supply terminal and a current source coupled between the control electrode of said one transistor and the further supply terminal, wherein the current source supplies a current to the control electrode of said one transistor. 
   
   
       17 . The electronic circuit of  claim 11 , wherein the output driver further includes a zener diode coupled between the control electrode of said one transistor and the supply terminal, wherein the zener diode limits a voltage between the control electrode of said one transistor and the first main electrode of said one transistor. 
   
   
       18 . The electronic circuit of  claim 11 , wherein the output driver further includes a further control circuit coupled to the control electrode of the other one of the transistors and configured to supply a further control signal to the control electrode of the other transistor.