Bandgap Reference Knee-Point Compensation for Low-Temperature Drift
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Solution Overview
Problem
Bandgap reference circuits in mixed signal integrated circuits experience voltage drift due to temperature variations, particularly at low temperatures, making it challenging to provide a stable reference voltage across different temperature ranges.
Innovation Solution
A piecewise compensation circuit that includes a knee code selector, output circuit, and trim DAC, configured to provide a correction current and compensation current to the bandgap reference circuit, setting knee point temperatures based on temperature sense signals and codes to compensate for temperature effects, thereby controlling the amplitude of the bandgap reference voltage across various temperature ranges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a bandgap reference circuit is used to provide a reference voltage, then the reference voltage can be generated for mixed signal integrated circuit applications, but the output voltage drifts as a function of temperature including at low temperatures
Solution Approach 1:
The temperature compensation is divided into multiple segments using different knee point temperatures (first knee point temperature and second knee point temperature) to address different temperature ranges separately. The circuit selectively activates different compensation paths based on the temperature range, with each segment optimized for its specific temperature region including low temperature operation.
Solution Approach 2:
The circuit changes the compensation parameters (knee point temperatures and trim codes) based on the operating temperature range. By adjusting the knee point temperature codes and trim codes, the compensation characteristics are optimized for different temperature conditions, particularly improving performance at low temperatures where standard bandgap references fail.
2Reliability
If temperature compensation is added to reduce voltage drift, then the temperature drift is reduced to less than 0.5-1.0 ppm/C, but the device complexity increases with additional circuits
Solution Approach 1:
The temperature sensing circuit and compensation circuit are merged into a unified structure where the same circuit elements serve multiple functions. The knee code selector and trim DAC are integrated with the bandgap reference circuit, allowing temperature compensation to be achieved without adding completely separate complex subsystems.
Solution Approach 2:
The compensation circuit is made dynamic through the knee code selector that automatically switches between different knee point temperature codes based on the operating temperature. This dynamic adaptation allows a single circuit to handle multiple temperature ranges, reducing the need for multiple fixed compensation circuits.
Data Source
AI summary
This description relates generally to piecewise temperature compensation. In an example, a circuit includes a knee code selector that can be configured to set a knee point temperature for a correction current responsive to a respective knee point temperature code of knee point temperature codes and a respective temperature sense signal of temperature sense signals. The circuit includes an output circuit that can be configured to provide the correction current responsive to the respective temperature sense signal and temperature voltages, and a trim digital to analog converter (DAC) that can be configured to provide a piecewise compensation current responsive to the correction current and a respective trim code of trim codes.