Programmable Voltage Generator Temperature Compensation
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Solution Overview
Problem
Conventional programmable voltage generators suffer from temperature-dependent errors due to bandgap bow, offset, and gain drift issues, which are not fully corrected by existing temperature compensating circuitry, leading to robustness concerns.
Innovation Solution
A programmable temperature compensated voltage generator using an on-chip digitizing temperature sensor and real-time Digital Signal Processing to compute a third-order polynomial correction coefficient, applied to a trim DAC and summed with the main DAC output before the output buffer, effectively correcting bandgap bow, offset, and gain drift errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional temperature compensating circuitry is used in the bandgap circuit, then some bandgap bow error is reduced, but temperature dependent errors from DAC and output buffer remain uncorrected
Solution Approach 1:
The patent separates temperature compensation into distinct functional blocks: a temperature sensor measures die temperature, a processor computes separate correction coefficients for bandgap bow, DAC offset drift, DAC gain drift, and buffer offset drift, and applies them through different circuit paths. This segmentation allows each error source to be corrected independently, resolving the contradiction by maintaining bandgap correction while adding comprehensive temperature error compensation that conventional unified circuitry cannot achieve.
Solution Approach 2:
The patent introduces a processor as an intermediary between temperature sensing and correction application. The processor receives temperature data, computes multiple correction coefficients using polynomial fitting, and generates separate correction signals for different circuit blocks. This intermediary enables sophisticated multi-parameter temperature compensation that goes beyond what direct conventional compensating circuitry can achieve, thereby improving overall temperature error robustness.
2Measurement precision
If trim circuits are added to correct offset and gain errors at one temperature, then trimming accuracy is improved, but temperature drift of trim circuit elements introduces new errors
Solution Approach 1:
The patent transitions from static trim circuits fixed at one temperature to dynamic temperature-dependent correction. The processor continuously computes correction coefficients based on real-time temperature measurements and applies them through DACs that adjust correction amounts dynamically. This dynamic approach eliminates the temperature drift problem of static trim circuits by continuously adapting correction values to current temperature conditions, thereby maintaining trimming accuracy across the full temperature range.
Solution Approach 2:
The patent changes the operational parameters of correction circuits from fixed values to temperature-variable values. Correction coefficients are computed as polynomial functions of temperature, allowing offset and gain corrections to automatically adjust with temperature changes. This parameter change strategy eliminates the need for temperature-stable trim circuit elements, resolving the contradiction by making correction values adaptive rather than static.
3Device complexity
If a simple bandgap reference is used, then circuit complexity is reduced, but temperature dependent output errors increase
Solution Approach 1:
The patent replaces complex analog temperature compensation circuitry with a digital processing approach. A processor computes correction coefficients using polynomial mathematics and applies them through digital-to-analog converters. This substitution of digital for analog complexity achieves superior temperature compensation accuracy while keeping the overall circuit structure manageable, resolving the contradiction by using computational rather than purely circuit-based complexity.
Solution Approach 2:
The processor serves multiple functions: sensing temperature, computing bandgap bow correction, computing DAC offset correction, computing DAC gain correction, and coordinating with the output buffer. This multi-functional approach consolidates what would otherwise require separate dedicated circuits for each correction function, achieving high precision temperature compensation without proportionally increasing circuit complexity.
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 solution significantly reduces temperature-dependent errors in voltage output, ensuring a more robust and accurate programmable voltage generation across varying temperatures.
Implementation Method 1
The generator uses an on-chip digitizing temperature sensor to measure the die temperature near a bandgap voltage reference circuit
Implementation Method 2
Real time Digital Signal Processing (DSP) is used to continuously compute a third order polynomial correction coefficient
Implementation Method 3
This coefficient is applied to a trim DAC and summed with a DAC output before an output buffer amplifier
Implementation Method 4
summed with a DAC output before an output buffer amplifier
Data Source
AI summary
A programmable temperature compensated voltage reference is disclosed. In an exemplary embodiment, an apparatus includes a digital-to-analog converter (DAC) that uses a reference voltage and a code to generate a DAC output voltage. The apparatus also includes a temperature compensator that uses a temperature measurement (T) and the DAC code to generate a temperature compensation signal. The temperature compensation signal is represented by a third order polynomial equation. The apparatus also includes a signal combiner that combines the DAC output voltage and the temperature compensation signal to generate a temperature compensated programmable reference voltage.