What does "great linearity" means for a ring oscillator?

Thread Starter

littlerock

Joined Feb 9, 2018
4
Hello all. I just want to ask the significance or meaning of the phrase "good linearity" or "great linearity" as an advantage for the design of a ring oscillator. I am reading a paper about a bootstrapped ring oscillator and it says that "the proposed ring oscillator provides great linearity while the ring oscillator is controlled by power supply regulation". What does it mean?
 

Thread Starter

littlerock

Joined Feb 9, 2018
4
Post more the text from the paper so we can have some context.
The Abstract of the paper is this:

"An ultra-low-power ring oscillator is presented in this paper. A bootstrapped CMOS delay cell is proposed to operate at 0.2 V - 0.6 V power supply. The proposed delay cell provides a boosted voltage swing to enhance the driving capability of the delay cell. Besides, the bootstrap technique suppresses the serious process variation in the low-voltage-supply design. As compared with conventional inverter-based ring oscillator, the proposed ring oscillator provides great linearity while the ring oscillator is controlled by power supply regulation. A test chip is
fabricated in the 90nm SPRVT Low-K CMOS process. Chip measurement results demonstrate that the proposed bootstrapped
ring oscillator can achieve 46 MHz at 0.2 V and 773 MHz at 0.6 V power supply. A 0.5 V 400 MHz ADPLL is verified in the test chip as well. The power consumption at 400 MHz operating clock is only 70 uW. The peak-to-peak jitter is 69.1 ps."
 

MrChips

Joined Oct 2, 2009
20,215
Linearity refers to the mathematical relationship between two parameters.
The fundamental equation of a straight line is:

y = mx + c

x = independent variable
y = dependent variable

in other words, y is dependent on x.
m = slope of the line (or gain of the relationship, m = y/x approx.)
c = is the offset

Generally, both m and c are constants. They do not change.
In particular, pertaining to your question, if m is constant, then the relationship between y and x is perfectly linear.

In real life, m may vary somewhat. That would determine the difference between "good linearity" and "great linearity".

What they are referring to is relationship between a control voltage and the resultant frequency of the oscillator. This would be called a voltage controlled oscillator.
 

Thread Starter

littlerock

Joined Feb 9, 2018
4
Linearity refers to the mathematical relationship between two parameters.
The fundamental equation of a straight line is:

y = mx + c

x = independent variable
y = dependent variable

in other words, y is dependent on x.
m = slope of the line (or gain of the relationship, m = y/x approx.)
c = is the offset

Generally, both m and c are constants. They do not change.
In particular, pertaining to your question, if m is constant, then the relationship between y and x is perfectly linear.

In real life, m may vary somewhat. That would determine the difference between "good linearity" and "great linearity".

What they are referring to is relationship between a control voltage and the resultant frequency of the oscillator. This would be called a voltage controlled oscillator.
Thanks for the response MrChips. Now, I understand. :)
 
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