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.
Claims29
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.
A 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.
A method of adjusting an oscillating signal, comprising:
- generating a signal oscillating for a resonant period during an oscillation cycle;
- and
- suspending oscillation for an interval equal to the difference between the resonant period and a predetermined period.
A method of adjusting a tank circuit resonant frequency which is less than a digital oscillator signal frequency, comprising:
- initiating a tank circuit oscillation cycle at a beginning of a digital oscillator oscillation cycle;
- and
- upon completion of the tank circuit oscillation cycle, compensating for a difference between a tank circuit oscillation period and a digital oscillator oscillation period by suspending tank circuit oscillation until completion of the digital oscillator oscillation cycle.
A pen circuit for a digitizing system, comprising:
- an inductor connected in parallel with at least one capacitor;
- 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.
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;
- and
- 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.
Dependencies are inferred from the claim text.