OSCILLATOR DEVICES AND METHODS THEREOF

• US 20080204155A1
• Filed: 02/28/2007
• Published: 08/28/2008
• Est. Priority Date: 02/28/2007
• Status: Active Grant

• Current Assignee: North Star Innovations Inc. (Wi-LAN Inc.)
• Original Assignee: Freescale Semiconductor, Inc. (NXP Semiconductors NV)
• Inventors: Olmos, Alfredo, Berens, Michael Todd, Soldera, Jefferson Daniel De Barros
• Granted Patent: US 7,733,191 B2
• Time in Patent Office: Days
• US Class Current: 331/108R
• CPC Class Codes: H03K 3/011 Modifications of generator to compensate for variations in physical values, e.g. voltage, temperature to maintain energy constant H03K3/015
• CPC Class Codes: H03K 3/354 Astable circuits

Abstract

Oscillator devices and methods of operating such oscillator devices are disclosed. The oscillator devices include a current source, and an oscillation module to provide a clock signal. The frequency of the clock signal depends on the relationship between a threshold voltage of a transistor at the oscillation module and the current level provided by the current source. The transistor at the oscillation module is matched to a transistor at the current source so that the frequency of the clock signal is relatively insensitive to changes in device temperature.

Claims

1. A device, comprising:

a current source comprising;

a first transistor comprising a first current electrode coupled to a first voltage reference, a second current electrode coupled to a second voltage reference, and a control electrode coupled to the second voltage reference;

a second transistor comprising a first current electrode coupled to the first voltage reference, a second current electrode coupled to the control electrode of the first transistor, and a control electrode coupled to the first current electrode of the first transistor; and

an output coupled to the first current electrode of the first transistor;

a switching module comprising;

a capacitor comprising a first current electrode responsive to a voltage at the output of the current source and a second current electrode coupled to the second voltage reference; and

a first control module comprising a third transistor that is matched with the first transistor, the third transistor comprising a first current electrode coupled to the first voltage reference, a second current electrode coupled to the second voltage reference, and a control electrode coupled to the first current electrode of the capacitor; and

a latch comprising a first input coupled to the first current electrode of the third transistor and a first output configured to provide a periodic signal based on a signal at the input.

2. The device of claim 1, wherein the switching module comprises a current mirror coupled to the control electrode of the third transistor.

3. The device of claim 1 further comprising a plurality of resistors coupled in series between the second current electrode of the second transistor and the second voltage reference.

4. The device of claim 3 wherein a first of the plurality of resistors comprises a N doped poly resistor and a second of the plurality of resistors is a P doped poly resistor.

5. The device of claim 1, wherein the first, second and third transistors are CMOS transistors.

6. The device of claim 1, wherein the switching module further comprises a first inverter coupled between the first current electrode of the third transistor and the input of the latch.

7. The device of claim 6, wherein the switching module further comprises a fourth transistor comprising a first current electrode coupled to the first current electrode of the capacitor, a second current electrode coupled to the second voltage reference and a control electrode coupled to an output of the second inverter.

8. The device of claim 7, wherein the latch is a toggle flip flop.

9. The device of claim 1, wherein the switching module further comprises a second control module comprising a fourth transistor that is matched with the first transistor, the fourth transistor comprising a first current electrode coupled to the first voltage reference, a second current electrode coupled to the second voltage reference, and a control electrode coupled to the second current electrode of the capacitor.

10. The device of claim 9, wherein the switching module further comprises:

a fifth transistor [734] comprising a first current electrode coupled to the first voltage reference, a second current electrode coupled to the second current electrode of the capacitor, and a control electrode coupled to a second output of the latch; and

a sixth transistor [736] comprising a first current electrode coupled to the first voltage reference, a second current electrode coupled to the first current electrode of the capacitor, and a control electrode coupled to the first output of the latch.

11. The device of claim 10, wherein the switching module further comprises:

a seventh transistor [740] comprising a first current electrode coupled to the second current electrode of the capacitor, a second current electrode coupled to the second voltage reference, and a control electrode coupled to the second output of the latch; and

an eighth transistor comprising a first current electrode coupled to the first current electrode of the capacitor, a second current electrode coupled to the second voltage reference, and a control electrode coupled to the first output of the latch.

12. The device of claim 11, wherein the latch is a set-reset flip flop.

13. A method comprising:

applying a first current to charge a capacitor to a first voltage level during a first interval, the first voltage level dependent on a first threshold voltage, the first threshold voltage dependent on a first temperature;

generating a first clock signal interval in response to the capacitor charge reaching the first threshold voltage; and

applying a second current to charge the capacitor to a second voltage level during a second interval, the second voltage level dependent on a second threshold voltage, the second threshold voltage dependent on a second temperature, the second temperature dependent on the first temperature; and

generating a second clock signal interval in response to the capacitor charge reaching the second threshold voltage, wherein the duration of the second interval is generally the same as the duration of the first interval.

14. The method of claim 13, further comprising discharging the voltage across capacitor to a ground at the end of the first interval.

15. The method of claim 13, wherein the first current is different from the second current.

16. The method of claim 15, further comprising providing an inverted representation of a signal from the first inverter to an input of a latch in response to switching first inverter transistor.

17. A device comprising:

an oscillator comprising a frequency variation of not greater than about 3.0 kHz over a temperature range of between about −

40°

C. and about 120°

C., at a voltage of not greater than about 5.5 Volts.

18. The device of claim 17, wherein the frequency variation is not greater than about 2.0 kHz at a voltage not greater than about 3.3V.

19. A device, comprising:

a current source generating a current dependent upon a voltage threshold of a first transistor;

a switching module for providing a switch control signal for latching, the switch control signal dependent upon the relationship between a capacitor charge and a first voltage level, the first voltage level based on a voltage threshold of a second transistor, the capacitor charge is proportional to the current; and

wherein a change in the voltage threshold of the first transistor due to a temperature change is generally matched by a change in the voltage threshold of the second transistor due to the temperature change.

20. The device of claim 19, wherein the first transistor and the second transistor are matched transistors.