VCO Current Mirror Biasing for Power Supply Noise Rejection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Voltage controlled oscillators (VCOs) in phase-locked loops face challenges in rejecting power supply noise without using a low drop out (LDO) regulator, which increases cost and power consumption due to the need for an extra power supply and additional chip area, while omitting the LDO regulator results in frequency variations and jitter.
Innovation Solution
Implementing a voltage controlled oscillator with operational transconductance amplifier (OTA) biasing that eliminates the need for an LDO regulator, providing power supply noise rejection through a current-biased circuit with programmable resistances and transistors, forming a current mirror to maintain stable current ratios and reduce frequency change and jitter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If an LDO regulator is used to minimize power supply voltage variations, then power supply noise rejection is improved, but cost and chip area increase due to extra power supply and additional components
Solution Approach 1:
The patent extracts the LDO regulator from the system and replaces it with a simplified current biasing circuit using transistors and programmable resistances. The current mirror circuit generates stable reference currents without requiring voltage regulation, thereby removing the harmful complexity of the LDO while maintaining power supply noise rejection through current stability.
Solution Approach 2:
The patent uses current mirror circuits to copy and replicate reference currents to multiple VCO cores. This copying mechanism ensures that all VCOs receive identical stable current references, providing power supply noise rejection through current replication rather than voltage regulation, thus reducing chip area and component count.
2Stability of the object's composition
If an LDO regulator is used to minimize power supply voltage variations, then frequency stability is improved, but power consumption increases due to extra power supply requirements
Solution Approach 1:
The patent implements self-service current biasing where the current mirror circuit automatically generates and maintains stable reference currents for the VCOs without external voltage regulation. The circuit uses the available power supply voltage directly and converts it to stable currents through transistor biasing and programmable resistances, eliminating the need for additional power supplies and reducing overall power consumption while maintaining frequency stability.
3Adaptability or versatility
If a large VCO gain and control voltage range are used to cover wide frequency range, then frequency coverage is improved, but sensitivity to power supply variations increases resulting in more jitter
Solution Approach 1:
The patent changes the biasing parameter from voltage-based to current-based control. By using programmable resistances and current mirror circuits, the system maintains large VCO gain and wide frequency coverage while achieving power supply noise rejection through current stability. The current biasing parameters can be programmed to optimize both frequency range and noise rejection performance.
Data Source
AI summary
An apparatus comprises a first circuit, a second circuit, a first transistor, a second transistor, a third transistor, a first programmable resistance, and a second programmable resistance. The first circuit may be configured to generate a reference signal and a bias signal in response to a supply voltage and a first input signal. The first circuit generally provides supply noise rejection to variations in the supply voltage. The second circuit may be connected to the first circuit and a ring oscillator. The first transistor may be connected to the first circuit and configured to set a first reference current of the first circuit based on the first input signal and the first programmable resistance. The second transistor may be connected in parallel with the first transistor. The second transistor is generally diode-connected. The third transistor may be connected to the first circuit and configured to set a second reference current of the first circuit based on the first input signal and the second programmable resistance. The first circuit generally forms a current mirror with the second circuit. The second circuit may be configured to provide a programmable current ratio for the current mirror based on a value of a second input signal.