Ring Oscillator With Improved Reliability
Original Publication Date: 1984-Jan-01
Included in the Prior Art Database: 2005-Feb-02
Present ring oscillators are constructed from an odd number of inverters connected in a continuous ring. Since there is an odd number of inverters in the ring, the ring is basically unstable and will oscillate. Presently, we measure the frequency of these oscillators, divide by the number of inverters in the ring, and hopefully determine the AC capability of a single logic block. Oscillators of this design are unreliable for they can oscillate in a multi-mode, and furthermore logic blocks in the chain may not fully switch but their output can be amplified and passed on, giving a false high speed reading. Fig. 1 is a block diagram of the disclosed ring oscillator. The delay element, which will be implemented from a string of inverters, is tapped at several points along its length.