Digital Bandgap Reference Using Multi-Current Diode Sampling
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Solution Overview
Problem
Conventional methods for determining a reference potential in signal conversion systems, such as those using the bandgap energy of semiconductor materials, suffer from inaccuracies due to device mismatch and temperature drift, leading to variations in the reference potential determination.
Innovation Solution
A circuit and method that alternately supplies different currents to a diode, measures the resulting voltage drops, and converts these measurements to a digital value to derive a constant representing the bandgap voltage, which is then used to generate a reference signal that is invariant to process and temperature variations, reducing errors and improving accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional analog bandgap reference methods are used, then the reference potential can be obtained, but accuracy is poor due to device mismatch and temperature drift causing up to 5% variation
Solution Approach 1:
The patent replaces the conventional analog bandgap reference system with a digital-based reference system. Instead of relying on analog voltage measurements across diodes with different areas, the invention uses digital-to-analog converters (DACs) to generate reference currents and digital processing to compute the reference voltage. This substitution of digital for analog mechanisms eliminates the sensitivity to device mismatch and temperature drift that plagues analog implementations, achieving the goal of improved accuracy and stability.
Solution Approach 2:
The patent changes the fundamental parameters of the reference generation system by using multiple different reference currents (I1, I2, I3, I4) instead of a single current, and by performing calculations in the digital domain. The system measures voltages at different current levels and uses digital processing to extract the reference voltage, thereby changing from a static analog measurement to a dynamic multi-parameter digital measurement system that is less susceptible to environmental variations.
2Ease of manufacture
If analog domain measurement is used for bandgap energy, then the measurement can be performed, but device mismatch causes significant accuracy degradation
Solution Approach 1:
The patent replaces the analog measurement approach with a digital measurement and processing approach. Instead of directly measuring and comparing analog voltages across mismatched devices, the system uses DACs to generate precise reference currents, measures the resulting voltages, and then performs digital calculations to determine the reference voltage. This digital substitution eliminates the direct impact of device mismatch on measurement accuracy while maintaining ease of manufacture through standard mixed-signal circuit techniques.
3Device complexity
If temperature drift compensation is not implemented, then the circuit remains simple, but the reference potential varies with temperature
Solution Approach 1:
The patent replaces complex analog temperature compensation circuits with a digital processing approach. Instead of using additional analog components and circuits to compensate for temperature drift, the system measures voltages at multiple current levels and uses digital calculations to extract temperature-invariant reference information. This substitution achieves temperature stability without significantly increasing overall circuit complexity.
Solution Approach 2:
The patent implements continuous monitoring and digital processing of voltage measurements taken at multiple current levels. By continuously measuring and processing the voltage-current relationships, the system maintains an accurate reference voltage that automatically compensates for temperature changes without requiring discrete compensation stages or additional control loops.
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
The solution significantly reduces accuracy errors related to device mismatch and temperature drift, achieving a more stable reference signal with improved consistency and cost-efficiency, especially in mixed-signal systems where digital domain processing is advantageous.
Implementation Method 1
a constant (VK) is determined by processing circuit 108... The constant (VK) represents a ratio of the bandgap voltage (VK) to Vref
Data Source
AI summary
A system and method (400) for producing a reference signal is provided. The method includes supplying (405) a first current to a diode, sampling (410) a first voltage across the diode, supplying (405) a second current to the diode, sampling (410) a second voltage across the diode, converting (415) the first voltage and the second voltage to a first digital value and a second digital value, and determining (420) a digital reference value from the first digital value and the second digital value. The first voltage is based on the first current, and the second voltage is based on the second current.