Self-Biased DCO Current Mirror for Linear Low-Power Tuning
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Solution Overview
Problem
Conventional digitally controlled oscillators (DCOs) in wireless communication systems face challenges in achieving frequency linearity across process, voltage, and temperature variations without consuming excessive power, especially in low-power applications, due to the need for error amplifiers and bandgap references.
Innovation Solution
A self-biased DCO design that eliminates the use of error amplifiers and bandgap references by employing a current mirror architecture with transistors M1 and M2, where the ratio of transistors M2 to M1 is adjusted by a digital codeword to set the control current, and voltage-divided control voltage is used to generate reference currents, allowing for frequency linearity without independent biasing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional DCO design with error amplifiers and bandgap references is used, then frequency linearity can be achieved, but power consumption increases
Solution Approach 1:
The patent removes the error amplifier and bandgap reference components from the conventional DCO architecture. By extracting these power-consuming elements and replacing them with a self-biased current mirror system, the design achieves frequency linearity without the excessive power consumption associated with traditional error correction mechanisms.
Solution Approach 2:
The DCO employs a self-biased architecture where the current mirror automatically generates the necessary bias currents without external error amplifiers. The system serves itself by using the control voltage directly to set the oscillation frequency through the current mirror ratio, eliminating the need for independent biasing circuits and reducing overall power consumption.
2Measurement precision
If conventional DCO design with error amplifiers and bandgap references is used, then frequency linearity can be achieved, but device area increases
Solution Approach 1:
The patent extracts and removes the error amplifier and bandgap reference blocks from the conventional DCO design. This extraction significantly reduces the device area by eliminating large analog circuits, replacing them with a compact current mirror implementation that achieves the same frequency linearity function with minimal area overhead.
Solution Approach 2:
The patent merges the frequency control function and biasing function into a single current mirror architecture. By combining these functions, the design eliminates the need for separate error amplifiers and bandgap references, thereby reducing device area while maintaining frequency linearity through the current mirror ratio control.
3Adaptability or versatility
If current mirror ratio is adjusted by digital codeword, then frequency tuning range is improved, but device complexity increases
Solution Approach 1:
The patent implements a dynamic current mirror ratio control mechanism where the ratio can be adjusted by a digital codeword. This dynamic adjustment capability allows the oscillator to tune across a wide frequency range while maintaining linearity, as the current mirror ratio adapts to the desired frequency output without requiring complex analog switching networks.
Solution Approach 2:
The patent replaces complex analog frequency tuning mechanisms with a digital control approach. By using a digital codeword to control the current mirror ratio, the design achieves wide frequency tuning range with simpler device architecture, substituting digital control logic for complex analog circuitry.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design reduces power consumption and area usage, enhancing the days of usage in low-power applications while maintaining frequency linearity, making it suitable for low-cost general-purpose PLLs.
Implementation Method 1
A self-biased DCO design that eliminates the use of error amplifiers and bandgap references by employing a current mirror architecture with transistors M1 and M2, where the ratio of transistors M2 to M1 is adjusted by a digital codeword to set the control current
Implementation Method 2
voltage-divided control voltage is used to generate reference currents
Data Source
AI summary
Certain aspects of the present disclosure are directed to a digitally controlled oscillator (DCO). The DCO generally includes an oscillator, a current mirror having a first branch coupled to a control input of the oscillator, a first current source, and a first transistor having a drain coupled to the first current source and a gate of the first transistor, a source of the first transistor being coupled to the control input of the oscillator. The DCO may also include a second current source coupled to the source of the first transistor, and a second transistor having a gate coupled to the gate of the first transistor, a drain of the second transistor being coupled to a second branch of the current mirror.