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US 6,587,098 B2Granted
High voltage crystal controlled oscillator for an electronic pen used with an electrostatic digitizing tablet
AssigneeLSI Logic Corporation
InventorJerzy A. Teterwak
Life of this patent
Estimating the term…
Abstract
A high Q tank circuit is employed at the output of a digital, crystal controlled oscillator to generate a high voltage amplitude signal. The tank circuit has a resonant frequency greater than the maximum required oscillation frequency. During each oscillation cycle, oscillation within the tank circuit is stopped in an energy efficient manner such that the resonant oscillation period is extended to match the required oscillation period. Modulation of the digital oscillator signal appears in the output circuit signal.
Claims14
An oscillator output circuit, comprising:
- a tank circuit receiving a digital oscillator signal having a signal period, the tank circuit oscillating with a resonant period which is less than the signal period;
- and
- a switch halting oscillation within the tank circuit for an interval equal to the difference between the signal period and the resonant period, wherein the oscillator output circuit may efficiently provide a high voltage amplitude signal,
- the tank circuit further including an inductor and at least one capacitor connected in parallel, wherein the switch shorts the inductor when a voltage across the at least one capacitor is zero, and
- the switch further includes:
- a diode connected to a first terminal of the inductor;
- and
- a bipolar junction transistor connected at an emitter to a second terminal of the inductor, at a collector to a cathode of the diode, and at a base to an input receiving a signal from the digital oscillator.
5 more elements
An oscillator circuit, comprising:
- a tank circuit connected between an output node and a ground, the tank circuit oscillating for a resonant period during an oscillation cycle;
- and
- a switch connected to the tank circuit, the switch suspending oscillation in the tank circuit for an interval equal to the difference between the resonant period and a predetermined period,
- wherein the tank circuit further includes:
- an inductor connected at a first terminal to the output node and at a second terminal to the ground;
- and
- at least one capacitor connected at a first terminal to the ground, and
- wherein the switch further includes:
- diode connected at an anode to the first inductor terminal;
- and
- a bipolar junction transistor connected at an emitter to the second inductor terminal, at a collector to a cathode of the diode, and at a base to an input receiving a control signal.
8 more elements
An oscillator output circuit, comprising:
- a tank circuit receiving a digital oscillator signal having a signal period, the tank circuit oscillating with a resonant period which is less than the signal period;
- a switch halting oscillation within the tank circuit for an interval equal to the difference between the signal period and the resonant period, wherein the oscillator output circuit may efficiently provide a high voltage amplitude signal, wherein the switch comprises:
- a diode connected to a first terminal of the inductor;
- a bipolar junction transistor connected at an emitter to a second terminal of the inductor, at a collector to a cathode of the diode, and at a base to an input receiving-a-signal from the digital oscillator;
- a field effect transistor connected at a source to the second terminal of the inductor, at a drain to the base of the bipolar junction transistor, and at a gate to an input receiving an inverted signal from the digital oscillator;
- wherein the tank circuit comprises an inductor and at least one capacitor connected in parallel;
- and
- wherein the switch shorts the inductor when a voltage across the at least one capacitor is zero.
5 more elements
An oscillator output circuit, comprising:
- a tank circuit receiving a digital oscillator signal having a signal period, the tank circuit oscillating with a resonant period which is less than the signal period, wherein the tank circuit comprises an inductor and at Least one capacitor connected in parallel;
- a switch halting oscillation within the tank circuit for an interval equal to the difference between the signal period and the resonant period, wherein the oscillator output circuit may efficiently provide a high voltage amplitude signal, wherein the switch shorts the inductor when a voltage across the at least one capacitor is zero;
- a second switch connecting the at least one capacitor to a power supply voltage when a voltage across the at least one capacitor is at a maximum;
- and
- a third switch connecting the at least one capacitor to a ground when the voltage across the at least on capacitor is at an opposite maximum.
2 more elements
A pen circuit for a digitizing system, comprising:
- an inductor connected in parallel with at least one capacitors;
- wherein the at least one capacitor further comprises a first capacitor and a second capacitor connected in series, a connection node between the inductor and the first capacitor forming an output node, a connection node between the inductor and second capacitor connected to a ground;
- a transistor connected in series with a diode, the transistor and the diode connected in parallel with the inductor and shorting the inductor when the transistor is on;
- and
- a controller turning on the transistor to selectively short the inductor, wherein the inductor and the at least one capacitor form a tank circuit oscillating with a resonant period, the controller turning on the transistor at the end of an oscillation cycle until a desired period has elapsed.
2 more elements
A data processing system, comprising:
- a host processing system;
- a digitizing tablet connected to the host processing system and receiving input signals from a pen, the digitizing tablet transmitting corresponding signals to the host processing system;
- a pen containing an oscillator circuit generating an output signal detected by the digitizing tablet, the output signal comprising a sinusoidal oscillation portion and a nonsinusoidal portion, wherein the oscillator circuit includes:
- an inductor connected at a first terminal to an output node for the output signal and at a second terminal to a ground node;
- a first capacitor connected at a first terminal to the output node and at a second terminal to an input node;
- a second capacitor connected at a first terminal to the input node and at a second terminal to the ground node;
- a diode connected at a first terminal to the output node;
- and
- a bipolar transistor connected at a collector to a second terminal of the diode and at an emitter to the ground node.
6 more elements
Dependencies are inferred from the claim text.