Digitally Reconfigurable Ultra High Precision Internal Oscillator

Abstract

This application relates to digitally reconfigurable ultra-high precision internal oscillators. Systems, methods and apparatus for tuning an internal oscillator to a desired frequency F1 are shown and use RC delay elements including resistors, capacitors and comparators. The method includes receiving a clock signal from an oscillator to be tuned, triggering charging of the RC delay element, and at N clock cycles after triggering said charging, the method determining whether the charge on the precision RC delay element is high or low at the reference voltage. Corrections to the clock frequency are based on this result.

Description

technical field [0001] The disclosed embodiments relate generally to the field of internal oscillators, and more particularly to providing a given frequency with high precision by means of an oscillator. Background technique [0002] Oscillators can be broadly classified as crystal oscillators and internal oscillators. A crystal oscillator can have a very stable frequency with an accuracy of parts per million (ppm) or parts per million. On the other hand, internal oscillators built entirely on a silicon chip or with one or a few external components (eg, resistors, capacitors, inductors, etc.) do not provide the same level of precision. For the internal oscillator, the best accuracy currently achievable is in the range of 0.5-1.0%; better accuracy is desired. [0003] To achieve high precision in an oscillator requires precise components inside or outside the correction loop. Such precision components can be implemented using one or more external components, such as off-ch...

AI Technical Summary

Problems solved by technology

Additionally, these high-accuracy solutions require trimming the process of accurately simulating RC

We did not previously have any method of trimming the internal resistor-capacitor (RC) time constant to 0.1%; therefore, we were not able to build a fully on-chip precision oscillator with this level of accuracy

Furthermore, non-idealities such as switch on-resistance, rise / fall times, incomplete settling, and parasitic coupling limit accuracy to more than about 0.5% in reasonable practical implementations

Furthermore, for chips containing multiple oscillators, each oscillator on the chip needs to be individually trimmed and tuned, which results in high test costs

Also, when a high-precision oscillator is tuned to one frequency, it is difficult to later tune the same oscillator to some other frequency with similar high precision

In some cases, such retuning is possible in small ranges but difficult in larger frequency ranges

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