DAC Cell Segmentation With Voltage Protection for Linear Power Output
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Solution Overview
Problem
Conventional Switched Capacitor (SC) and Switched Current (SI) Digital Power Amplifiers (DPAs) face challenges in achieving low supply impedance and high linearity for cellular applications, leading to excessive AM-PM and AM-AM distortions, LO leakage, and increased complexity, especially at high output power levels.
Innovation Solution
A DAC circuit design that separates voltage protection from the DAC cell field, using a voltage protection circuit to regulate voltage and reduce the size and complexity of the DAC cell field, allowing for improved matching and reduced distortions by decoupling supply lines from output lines and using switchable current sources for efficient biasing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the switching capacitance is scaled to increase output power, then the output power increases, but the size of the DAC cell field increases and parasitic inductance increases
Solution Approach 1:
The patent divides the large DAC cell field into multiple smaller sub-cell fields, each with its own voltage protection circuit. This segmentation reduces the parasitic inductance within each sub-field while maintaining the overall output power capability through parallel operation of multiple cells.
Solution Approach 2:
The voltage protection circuits are extracted from individual DAC cells and implemented as shared resources for groups of cells. This reduces the per-cell complexity and allows the DAC cell field to be scaled without proportionally increasing the protection circuitry size.
2Power
If the DAC cell field size increases to provide higher output power, then the output power increases, but the matching between DAC cells becomes difficult and supply impedance increases
Solution Approach 1:
By segmenting the DAC cell field into smaller groups with shared voltage protection circuits, the patent ensures better matching within each segment. The reduced size of each segment minimizes variations in parasitic inductance and supply impedance, improving overall matching precision.
Solution Approach 2:
Each segment of the DAC cell field is designed with locally optimized voltage protection circuits that are tailored to the specific requirements of that segment. This local quality approach ensures that each segment operates with optimal matching characteristics.
3Stress or pressure
If the supply voltage is increased to overcome supply impedance issues, then the voltage swing increases, but the switch impedance and complexity increase due to transistor stacks
Solution Approach 1:
The voltage protection function is extracted from the individual DAC cells and implemented as separate circuits that can operate at optimized voltage levels. This allows the DAC cells themselves to use simpler switch structures without the complexity of high-voltage transistor stacks.
Solution Approach 2:
The voltage protection circuits act as intermediary elements between the DAC cell field and the output node. These circuits handle the high-voltage swing requirements while allowing the DAC cells to operate with lower impedance switches, thus mediating between the conflicting requirements.
4Power
If a large cell field is used to achieve high output power, then the output power increases, but LO leakage to the output increases and system specifications deteriorate
Solution Approach 1:
The patent segments the large cell field into smaller groups, each with its own voltage protection circuit. This segmentation reduces the total capacitance connected to any single LO signal, thereby reducing LO leakage while maintaining the overall output power through parallel operation of multiple segments.
Data Source
AI summary
A digital-to-analog converter circuit including one or more digital-to-analog converter cells and a separate voltage protection circuit connected by a common output node. A first digital-to-analog converter cell includes a first transistor which is configured to be switched to a conductive state when the first digital-to-analog converter cell is activated. A first terminal of the first transistor is coupled to a defined potential, wherein a second terminal of the first transistor is coupled to a common output node of the one or more digital-to-analog converter cells. The digital-to-analog converter circuit further includes a voltage protection circuit coupled between the common output node of the one or more digital-to-analog converter cells and an output node of the digital-to-analog converter circuit to regulate a voltage between the common output node and the defined potential.