Temperature correcting current-controlled ring oscillators

Abstract

A thermally-compensated oscillator has a current reference with an output current which relates to an ambient temperature with a first relationship, a ring oscillator having an operating frequency which relates to the ambient temperature with a second relationship, and which receives the output current of the current reference and outputs an oscillator signal, and a level shifter which receives the oscillator signal from the ring oscillator and outputs a corresponding voltage-regulated clock signal.

Description

FIELD OF THE INVENTION[0001]This invention relates generally to current-controlled ring oscillators, and, more specifically, to regulating a frequency of a current-controlled ring oscillator's output signal in accordance with ambient temperature.BACKGROUND OF THE INVENTION[0002]Many integrated circuit devices require stable oscillators to provide the reference clocks used in the system. Since virtually all integrated circuit devices operate in environments whose temperature fluctuates, such a reference clock should exhibit a stable oscillating frequency over a range of operating temperatures. Furthermore, it is desirable for a reference clock to exhibit a stable oscillating frequency over a range of operating voltages, and also not be affected by process variations which might arise during device manufacture.[0003]Many applications necessitate that the device's power consumption be made as small as possible; for example, battery powered devices and / or RFID (radio frequency identific...

AI Technical Summary

Benefits of technology

[0011]This invention proposes a scheme for temperature correcting a current controlled ring oscillator, preferably to thereby provide a stable clock reference over temperature fluctuations (and, possibly (by careful design), supply voltage variations). The proposed solution has the advantage that it requires minimal silicon area as compared to other solutions, such as an RC oscillator, operates at low power supply levels and is relatively temperature independent.

Problems solved by technology

In the case of battery powered devices, decreasing power consumption can increase the time required until battery recharging or replacement is required, and / or permit the use of a battery storing less power (which, typically, is a smaller, lighter and less costly battery).

It is therefore likely that a device using a ring oscillator to provide a clock signal will experience temperature fluctuations, resulting in temperature-induced variations in the clock signal by that ring oscillator.

Such clock signal variations could undesirably affect device performance, or require the inclusion of compensating components or logic in the device to cope with those variations.

Current solutions to this problem are not satisfactory.

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