Delta-Sigma Clock Generation With Tail-Current Phase Control
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Solution Overview
Problem
Conventional delta sigma modulators face challenges in increasing the delay time of clocks significantly due to the limitations of the number of inverters in the clock generation circuit, and adjusting the frequency of the input clock affects the phase correlations among the clocks.
Innovation Solution
A delta sigma modulator with a clock generation circuit featuring a ring oscillator composed of differential amplifiers and operational amplifiers, generating clocks with varying phases, and a switching circuit controlled by these clocks, where the tail currents through the amplifiers are made proportional to maintain phase correlations, allowing for flexible adjustment of clock delay times.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If the number of inverters in the delay circuit is increased to increase the delay time of clocks, then the delay time increases, but the device complexity increases significantly
Solution Approach 1:
The patent changes the control parameter from the number of inverters to the tail current value. By adjusting the tail current value in the differential amplifiers, the delay time of clocks can be continuously adjusted without increasing the number of circuit components. This resolves the contradiction by providing a parameter (current value) that can be varied to achieve the desired delay time without adding circuit complexity.
2Productivity
If the frequency of the input clock is varied to modify the operational frequency, then the operational frequency changes, but the phase correlations among clocks are disrupted
Solution Approach 1:
The patent implements a feedback mechanism where the tail current values of the differential amplifiers are adjusted based on the operating frequency to maintain constant phase differences. The control circuit monitors the frequency and automatically adjusts the tail currents to compensate for frequency variations, ensuring that phase correlations are maintained across different operating frequencies. This resolves the contradiction by providing automatic adaptation to frequency changes.
Solution Approach 2:
The patent uses parameter changes in the tail current values to maintain phase correlations at different frequencies. By dynamically adjusting the tail current parameter based on the operating frequency, the system maintains stable phase relationships without requiring a fixed frequency operation, thus resolving the contradiction between frequency flexibility and phase stability.
3Loss of time
If the delay time of clocks is adjusted by changing the number of inverters, then the delay time changes, but it becomes difficult to increase the delay time significantly
Solution Approach 1:
The patent transitions from discrete adjustment (number of inverters) to continuous adjustment (tail current value). By controlling the tail current parameter, the delay time can be adjusted continuously over a wide range, including significant increases in delay time that would be impractical with inverter-based approaches. This provides both fine-grained control and extensive adjustability range.
Data Source
AI summary
With a delta sigma modulator of this invention, a plurality of clocks required to control a switching circuit can be easily generated and correlation among phases of the plurality of clocks can be automatically maintained while a frequency of the clocks is modified. A ring oscillator is formed of three delay circuits provided with differential amplifiers in the delta sigma modulator. A clock producing circuit produces the plurality of clocks to control the switching circuit by delaying three-phase clocks outputted from the ring oscillator. All the tail currents Ic in the differential amplifiers in the delay circuits in the ring oscillator and the tail currents Ic in the differential amplifiers in the delay circuits in the clock producing circuit are proportional to each other.