Periodic Kick-Starter For A Crystal Oscillator

Patent metadata

Field	Value
Publication number	US-2016373056-A1
Application number	US-201615186034-A
Country	US
Kind code	A1
Filing date	Jun 17, 2016
Priority date	Jun 22, 2015
Publication date	Dec 22, 2016
Grant date	—

Abstract

A cyclical pulsing oscillator having a pulse repetition rate close to a crystal resonant frequency in an oscillator provides more useful start-up energy to the crystal oscillator circuit and thus provides much faster start-up time. The start-up pulsing oscillator runs for a number of cycles or until the crystal oscillator amplitude as built up to a desired value. The pulsing oscillator may have a repetition rate of from about one-third to about one-half the crystal resonant frequency, thus providing more useful start-up energy to the crystal oscillator circuit.

First claim

1 . An integrated oscillator configured to be coupled with an external crystal, comprising:
an oscillator circuit coupled with the external crystal; and a start-up circuit comprising a kick-start pulser coupled to the oscillator circuit and pulsing start-up energy thereto.

2 . The integrated oscillator according to claim 1 , wherein the kick-start pulser comprises a current source charging a capacitor, a discharging switch coupled in parallel with the capacitor wherein a node between the current source and the capacitor is coupled to an input of a comparator whose output controls the discharging switch, and a pulsing switch controlled by the comparator and coupled to the oscillator circuit.

3 . The integrated oscillator according to claim 1 , wherein the comparator has hysteresis.

4 . The integrated oscillator according to claim 2 , further comprising a digital counter which disables the start-up circuit after a predetermined number of pulses generated by the start-up circuit.

5 . The integrated oscillator according to claim 4 , wherein the predetermined number of pulses is from about 16 to about 32 pulses.

6 . The integrated oscillator according to claim 4 , wherein the predetermined number of pulses is from about 32 to about 64 pulses.

7 . The integrated oscillator according to claim 1 , wherein a frequency of the kick-start pulser is from about one-third to about one-half of a center frequency of the external crystal.

8 . The integrated oscillator according to claim 1 , wherein a frequency of the kick-start pulser is within a decade of a center frequency of the external crystal.

9 . The integrated oscillator according to claim 1 , wherein a frequency of the kick-start pulser is within a bandpass frequency of the external crystal.

10 . A microcontroller comprising the integrated oscillator according to claim 1 .

11 . The microcontroller according to claim 10 , wherein the microcontroller is configured to turn off the start-up circuit after the oscillator circuit has a stable oscillation amplitude.

12 . The microcontroller according to claim 10 , wherein the microcontroller is configured to turn off the start-up circuit after a predetermined time period after the microcontroller starts operating.

13 . The integrated oscillator according to claim 1 , wherein the oscillator circuit comprises:
a current source coupled to a supply voltage; a first resistor coupled to a bias voltage; a first capacitor coupled to the first resistor; a second resistor coupled to the first capacitor; a first transistor coupled to the current source, first capacitor, and first and second resistors; a second capacitor coupled to the first capacitor and second resistor; a third capacitor coupled to the second resistor and first transistor; a second transistor coupled to the first, second and third capacitors, the second resistor and the first transistor; and the external crystal coupled to the first and second transistors; the first, second and third capacitors; and the second resistor.

14 . A integrated oscillator, comprising:
a crystal oscillator; a kick-start pulser coupled to the crystal oscillator; a oscillator cycle counter coupled to the crystal oscillator; and a logic gate for enabling and disabling an oscillator clock output; wherein the oscillator cycle counter will disable the kick-start pulser and enable the oscillator clock output from the logic gate after a certain number of cycles from the oscillator are counted.

15 . The integrated oscillator according to claim 14 , wherein the kick-start pulser comprises a current source charging a capacitor, a discharging switch coupled in parallel with the capacitor wherein a node between the current source and the capacitor is coupled to an input of a comparator whose output controls the discharging switch, and a pulsing switch controlled by the comparator and coupled to the oscillator circuit.

16 . The integrated oscillator according to claim 14 , further comprising a kick-start pulser counter coupled to the kick-start pulser, wherein the kick-start pulser will be disabled after a certain number of pulses are counted by the kick-start pulser counter.

17 . A microcontroller comprising the integrated oscillator according to claim 14 .

18 . A integrated oscillator, comprising:
a crystal oscillator; a kick-start pulser coupled to the crystal oscillator; a logic gate for enabling and disabling an oscillator clock output; an oscillator output amplitude detector coupled to the crystal oscillator; a voltage reference providing a reference voltage; and a voltage comparator having a first input coupled to the oscillator output amplitude detector, and a second input coupled to the voltage reference, wherein when the detected oscillator output amplitude is greater than the reference voltage the kick-start pulser is disabled and the logic gate is enabled to provide the oscillator clock output.

19 . The integrated oscillator according to claim 18 , wherein the kick-start pulser comprises a current source charging a capacitor, a discharging switch coupled in parallel with the capacitor wherein a node between the current source and the capacitor is coupled to an input of a comparator whose output controls the discharging switch, and a pulsing switch controlled by the comparator and coupled to the oscillator circuit.

20 . A microcontroller comprising the integrated oscillator according to claim 18 .

21 . A method for starting an integrated oscillator configured to be coupled with an external crystal, said method comprising the steps of:
coupling an oscillator circuit to the external crystal; and pulsing energy into the oscillator circuit with a kick-start pulser coupled.

22 . The method according to claim 21 , wherein the step of pulsing energy into the kick-start pulser comprises the steps of:
charging a capacitor with a current source; discharging the capacitor with a switch that is controlled by a comparator that has hysteresis when a voltage on the capacitor is reached; switching on and off a pulsing switch with the comparator, wherein the pulsing switch provides the pulsing energy to the oscillator circuit.

Assignees

• Microchip Tech Inc

Inventors

• Kumar Ajay

Classifications

• H03K21/38

  Starting, stopping or resetting the counter (counters with a base other than a power of two H03K23/48, H03K23/66) · CPC title

• H03K3/02337

  Bistables with hysteresis, e.g. Schmitt trigger (non-regenerative amplitude discriminators G01R19/165) · CPC title

• H03B5/364 Primary

  the amplifier comprising field effect transistors (H03B5/366 takes precedence) · CPC title

• H03B5/06 Primary

  Modifications of generator to ensure starting of oscillations · CPC title

• H03B5/366

  and comprising means for varying the frequency by a variable voltage or current · CPC title