Single-Junction Voltage Reference Using Time-Multiplexed Current Drive
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Solution Overview
Problem
Existing voltage references are either too costly or provide poor performance, often consuming significant power and being sensitive to external support circuitry, making it challenging to achieve high-performance, cost-effective board-level solutions.
Innovation Solution
A single semiconductor-based junction is used to create and temperature-compensate a voltage reference by time-multiplexing current drive levels, switching currents between forward and reverse directions, or using diode-connected bipolar junction transistors with alternating currents to achieve a zero temperature coefficient reference voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If multiple circuit-configurations are used to generate temperature-stable voltages in voltage-reference ICs, then temperature stability is improved, but device complexity and cost increase
Solution Approach 1:
The patent combines multiple voltage reference configurations (zener diode and forward-biased junction) into a single integrated circuit that operates at different temperatures. The system merges the temperature-independent reference (zener) and temperature-dependent reference (forward-biased junction) into one device, using a temperature sensor to dynamically select or combine references based on operating conditions, thereby achieving temperature stability without requiring separate complex circuits for each temperature range.
Solution Approach 2:
The patent introduces dynamic temperature compensation by using a temperature sensor to monitor junction temperature and automatically adjusting the reference voltage selection or combination ratio. This dynamic adaptation allows the voltage reference to maintain stability across varying temperatures without requiring manual calibration or fixed complex circuitry for each temperature scenario.
2Ease of manufacture
If zener diodes are used for voltage reference, then cost is reduced, but temperature coefficient performance deteriorates
Solution Approach 1:
The patent introduces a temperature sensor as an intermediary element that monitors the temperature of the zener diode and uses this information to compensate for temperature drift. By measuring the actual temperature and adjusting the reference voltage accordingly (either by selecting alternative references or combining references in adjusted ratios), the system maintains accurate voltage reference performance while continuing to use the cost-effective zener diode structure.
3Device complexity
If IC-based references are used, then integration is improved, but noise increases
Solution Approach 1:
The patent extracts the critical high-precision voltage reference function from the integrated circuit environment and implements it using discrete zener diodes and forward-biased junctions that are known to have lower noise characteristics. By removing the reference generation from the noisy IC environment and using separate, properly-biased discrete components, the system achieves lower noise while maintaining integration through careful circuit design and temperature compensation.
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 provides a stable, high-performance voltage reference that is cost-effective and less sensitive to external circuitry, reducing noise and temperature sensitivity, while allowing for implementation at the board level.
Implementation Method 1
The single junction may be in a zener diode... adding one or more forward-biased junctions in series with a reverse-biased zener junction (technically, an avalanche junction)
Implementation Method 2
As illustrated by diagrams 206 and 208, the respective temperature coefficients of the voltage across junction 202 and the voltage across junction 204 have different ppm/° C. (parts-per-million/° C.) values, and yield a stable reference voltage between terminals 212 and 214
Implementation Method 3
A bandgap reference operates on the basis that a pair of BJTs (bipolar junction transistors) operating at different collector current densities have different Vbe (base-emitter voltage) temperature coefficients
Implementation Method 4
Adding the voltages of the two junctions in the proper proportion yields a voltage that is largely temperature independent
Data Source
AI summary
A single semiconductor-based junction may be used to create a voltage reference, and temperature compensate the voltage reference, by time-multiplexing the voltage reference between different current drive levels. That is, the value of the current driven through the single junction may be repeatedly varied in a recurring manner. In case the junction is a zener diode, the current may be repeatedly switched between forward and reverse directions. As long as the temperature coefficients (in ppm/° C.) of the different voltages developed responsive to the different currents across the junction are different, a weighting of the different voltage values yield a zero temperature coefficient voltage reference value. To implement a bandgap reference, a single diode-connected bipolar junction transistor may alternately be forward-biased using a first current and at least a second current. A weighting of the (at least) two resulting Vbe (base-emitter voltage) drops may yield a zero temperature coefficient bandgap voltage.