Feedback-Biased DCO Circuit for PVT-Stable Oscillation
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Solution Overview
Problem
Digitally controlled oscillators (DCOs) face variability in performance due to changes in process, voltage, and temperature (PVT), leading to unstable oscillation signal frequencies, which affects the stability of integrated circuits.
Innovation Solution
A DCO design incorporating a current mirror, a variable resistor, and a feedback circuit with an amplifier that generates negative feedback to stabilize the bias voltage, reducing sensitivity to PVT variations and maintaining stable oscillation signal frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional DCO structure is used, then the circuit complexity is low, but the oscillation frequency becomes sensitive to PVT variations
Solution Approach 1:
The patent implements a feedback circuit that detects voltage variations at the first node (caused by PVT changes) and adjusts the bias voltage of the current mirror accordingly. The feedback circuit includes an amplifier that compares the voltage at the first node with a reference voltage and generates a correction signal to stabilize the supply current to the oscillation circuit, thereby maintaining stable oscillation frequency despite PVT variations.
Solution Approach 2:
The patent dynamically adjusts the bias voltage parameter of the current mirror based on detected voltage variations. By changing the bias voltage in response to PVT conditions, the supply current to the oscillation circuit is maintained at a stable level, compensating for the effects of process, voltage, and temperature variations on oscillation frequency.
2Reliability
If additional circuitry is added to stabilize bias voltage, then PVT insensitivity is improved, but device complexity increases
Solution Approach 1:
The feedback circuit is integrated with the existing current mirror and oscillation circuit structures. The amplifier shares the same supply voltage and is coupled to existing nodes within the DCO, merging the stabilization function into the existing circuit architecture rather than adding completely separate stabilization circuits.
Solution Approach 2:
The feedback circuit automatically detects and corrects voltage variations without requiring external control signals or additional stabilization components. The system self-regulates by using the voltage variation detection at the first node to generate the necessary bias voltage adjustment, making the circuit self-stabilizing against PVT variations.
Data Source
AI summary
A digitally controlled oscillator (DCO) includes; a current mirror configured to generate a supply current in response to a bias voltage matching a reference current, a variable resistor connected to the current mirror through a first node outputting the reference current and configured to provide a variable resistance in response to a first control signal, an oscillation circuit connected to the current mirror through a second node outputting the supply current and configured to generate an oscillation signal in response to the supply current, and a feedback circuit configured to control the bias voltage in relation to at least one of a voltage at the first node and a voltage at the second node.