Method and apparatus for reducing transient noise by premagnetization of parasitic inductance

An output driver in an integrated circuit for reducing the level of transient noise generated by the integrated circuit during the driving of an external electrical device in response to an input signal, where the external electrical device has a characteristic capacitance and the integrated circuit has a parasitic inductance, the output driver comprising:

• power supply means for supplying electrical power;
• an input terminal for receiving the input signal;
• an output terminal for connecting the output driver to the external electrical device;
• first switch means, coupled to the power supply means and the parasitic inductance, for selectively electrically connecting the power supply means with the parasitic inductance of the integrated circuit;
• second switch means, coupled to the power supply means and the output terminals, for selectively electrically connecting the power supply means with the external electrical device;
• third switch means, coupled to the output terminal and the parasitic inductance, for selectively electrically connecting the external electrical device and the parasitic inductance of the integrated circuit;
• and
• delay means, coupled to the input terminal and the second and third switch means, for delaying the activation of the second and third switch means for a predetermined amount of time after activation of the first switch means.

An output driver in an integrated circuit for reducing the level of transient noise generated by the integrated circuit during the driving in response to a supplied input signal of an external electronic device having a characteristic capacitance, the integrated circuit having a parasitic inductance, the output driver comprising:

• power supply means for supplying electrical power;
• current source means for supplying current of a predetermined maximum magnitude;
• an input terminal for receiving the input signal;
• an output terminal for connecting the output driver to the the external electronic device;
• first switch means, coupled to the power supply means and the current source means, for selectively electrically connecting the power supply means with the current source means, thereby selectively activating the current source means to supply a first current of a predetermined maximum magnitude to the parasitic inductance of the integrated circuit;
• second switch means, coupled to the power supply means and the output terminal, for selectively electrically connecting the power supply means and the external electronic device, thereby electrically charging the capacitance of the external electronic device;
• third switch means, coupled to the output terminal and the current source means, for electrically connecting the external electronic device and the current source means, thereby selectively activating the current source means to supply a second current of a predetermined maximum magnitude through the output terminal to the parasitic inductance of the integrated circuit as the characteristic capacitance of the external electronic device discharges;
• and
• delay means, coupled to the input terminal and the second an third switch means, for delaying the activation of the second and third switch means for a predetermined amount of time after activation of the first switch means.

A method for reducing the level of transient noise generated by an integrated circuit during the driving of an external electronic device having a characteristic capacitance, comprising the steps of:

• (1) providing an integrated circuit having a parasitic inductance, power supply terminals for supplying a power supply voltage and a bias current, and an output driver connected to the external electronic device, the power supply terminals and the parasitic inductance;
• (2) charging the capacitance of the external electronic device with the power supply voltage;
• (3) passing the bias current through the parasitic inductance to thereby presoak the inductance, and
• (4) approximately simultaneously (a) commencing to reduce the magnitude of the bias current through the parasitic inductance and (b) commencing to drive the external electronic device to allow the charged capacitance of the external electronic device to discharge through the parasitic inductance.

A method for reducing the transient noise generated during activation of an electronic device, said electronic device having a parasitic inductance, said method consisting of:

• providing current means for passing a current of predetermined value through said parasitic inductance of said electronic device;
• activating said current means at a predetermined amount of time prior to activation of said electronic device, thereby presoaking said parasitic inductance with current;
• activating said electronic device;
• and
• deactivating said current means when said electronic device is activated.