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US 8,526,635 B2Granted
Grounding switch method and apparatus
AssigneeConexant Systems, Inc.
InventorsChristian Larsen, Lorenzo Crespi
Life of this patent
Estimating the term…
Abstract
A grounding switch is described which operates properly even in the presence of negative voltages on a signal line. The grounding switch uses isolated field effect transistors that have their substrates tied to different voltages. The isolated field effect transistor has a gate voltage and substrate voltage which can be pulled down to a negative voltage when the signal line has a negative voltage allowing the switch to remain open even with a negative voltage.
Claims15
A switch connecting a first signal line and a second signal line comprising:
- a first isolated n-channel field effect transistor (NFET) with an isolated substrate connection, having a gate and a drain, wherein the drain is coupled to the first signal line;
- a second NFET having a gate coupled to a control signal and a source coupled to the second signal line, wherein the second NFET is in series with the first isolated NFET;
- a controlled pull-up circuit operable to receive the control signal, the controlled pull-up circuit coupled to the gate of the first isolated NFET;
- and
- a pull-down circuit coupled to the gate of the first isolated NFET;
- wherein the pull-up circuit pulls up the gate of the first isolated NFET to a positive supply voltage when the control signal is in a high state;
- and
- wherein the pull-down circuit pulls the gate of the first isolated NFET down to a negative supply voltage or the voltage of the first signal line when the control signal is in a low state.
5 more elements
In an electronic device, an audio driver comprising:
- an amplifier stage;
- an output stage comprising an output driver, a resistor and a capacitor;
- and
- a grounding switch;
- wherein the amplifier stage is coupled to the output stage and the grounding switch is coupled to an output of the output stage;
- and
- wherein the grounding switch comprises:
- a first isolated NFET with an isolated substrate connection, having a gate and a drain;
- a second NFET having a gate coupled to a control signal, wherein the second NFET is in series with the first isolated NFET;
- a controlled pull-up circuit operable to receive a control signal, coupled to the gate of the first isolated NFET;
- and
- a pull-down circuit coupled to the gate of the first isolated NFET;
- wherein the pull-up circuit pulls up the gate of the first isolated NFET to a positive supply voltage when the control signal is in a high state;
- and
- wherein the pull-down circuit pulls the gate of the first isolated NFET down to a negative supply voltage or the voltage of the first signal line when the control signal is in a low state.
12 more elements
Dependencies are inferred from the claim text.