Precise On-Board Tuning of Embedded Microcontroller Oscillator Using Charge Time Measurement Unit

Abstract

Accurate measurement of the period of the embedded clock oscillator using the charge time measurement unit CTMU maintains the desired frequency accuracy of the embedded clock oscillator over time, temperature, and operating condition variations. The CTMU determines the free-running frequency of the embedded clock oscillator and provides very accurate frequency (period) information used to confirm that the desired frequency (e.g., within 0.25% of the desired frequency) is running or convert the clock to An indication of how much and in which direction the frequency of an oscillator is adjusted to maintain the desired frequency accuracy. Automatic frequency adjustment of the embedded clock oscillator can be implemented in order to maintain its desired precise frequency. The temperature and voltage compensation profiles used to maintain the accuracy of the CTMU may be stored in a table, such as in non-volatile memory, for further improving the absolute frequency accuracy of the embedded clock oscillator .

Description

technical field [0001] The present invention relates to integrated circuit devices requiring a precision clock oscillator, and more particularly to integrated circuit devices having a precision clock oscillator integrated with the integrated circuit device. Background technique [0002] As integrated circuit devices incorporate more sophisticated and complex peripheral devices, precise run-time control of internal clock oscillators is required. For example, USB2.0 integrated peripherals must meet a clock frequency accuracy of 0.25%. A typical application will have to use an external crystal to control the clock frequency within the stated accuracy. However, an external crystal frequency determination device requires two integrated circuit pins for connection to the internal oscillator circuit in said integrated circuit device. This poses a problem for low pin count integrated circuit devices since two of the very few package pins must be dedicated to the external crystal. ...

AI Technical Summary

Problems solved by technology

But there is a problem because the internal self-contained RC oscillator can drift in frequency, even if the oscillator is precisely calibrated when the integrated circuit device is manufactured

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