Capacitive DAC Architecture for Low-Power Wireless Transmitters
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Solution Overview
Problem
Previous transmitter architectures using current steering DACs suffer from non-linearities and low efficiency due to power wastage by current sources, necessitating a more efficient solution for digital-to-analog conversion in wireless transmitters.
Innovation Solution
The implementation of capacitive DAC cells with passive capacitor elements reduces the number of transformers needed, allowing for a more efficient and area-saving architecture by converting digital signals to analog signals using capacitive cells instead of current steering cells.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If current steering DAC cells are used, then digital to analog conversion can be achieved, but power consumption increases and efficiency decreases due to power wastage by current sources
Solution Approach 1:
The patent replaces current steering cells with capacitive DAC cells, substituting the mechanical/electrical current source system with a capacitive system that stores and releases charge. This substitution eliminates the continuous power consumption inherent in current sources while maintaining the digital to analog conversion function.
Solution Approach 2:
The invention changes the fundamental operating parameter from current-based conversion to charge-based conversion. By using capacitors to store charge representing digital values and selectively discharging them to create analog output currents, the system achieves conversion without the continuous power wastage of traditional current sources.
2Device complexity
If current steering DAC architecture is used, then digital to analog conversion is achieved, but the number of transformers increases and silicon area expands
Solution Approach 1:
The patent extracts and eliminates the transformer component from the DAC architecture by using capacitive cells that directly generate the analog output current. This removal of unnecessary components reduces both device complexity and the silicon area required for implementation.
3Loss of energy
If capacitive DAC cells are used instead of current steering cells, then power consumption is reduced and efficiency is enhanced, but manufacturing precision requirements may increase
Solution Approach 1:
The invention changes the critical manufacturing parameter from current source precision to capacitor ratio precision. While capacitor precision is important, it is generally more achievable in standard CMOS fabrication processes compared to the precision required for current sources, thus resolving the contradiction between energy efficiency and manufacturing precision.
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 approach reduces silicon area and manufacturing costs, lowers power consumption, and enhances efficiency by eliminating unnecessary transformers, resulting in a more streamlined transmitter design.
Implementation Method 1
The DAC includes a digital signal input configured to receive a multi-bit digital input signal, and an array of cells. Respective cells in the array comprise respective capacitors. The DAC also includes a control circuit configured to, based on the multi-bit digital input signal, selectively induce one or more corresponding capacitors to discharge current to an output terminal of the DAC.
Data Source
AI summary
Some examples relate to a digital to analog converter (DAC). The DAC includes a digital signal input configured to receive a multi-bit digital input signal, and an array of cells. Respective cells in the array comprise respective capacitors. The DAC also includes a control circuit configured to, based on the multi-bit digital input signal, selectively induce one or more corresponding capacitors to discharge current to an output terminal of the DAC.