Voltage Reference Circuit Temperature Drift Compensation
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Solution Overview
Problem
Existing voltage reference circuits are affected by temperature drift and higher-order errors, requiring trimming circuits to maintain target specifications, which can be complex and error-prone.
Innovation Solution
A voltage reference circuit that combines proportional to absolute temperature (PTAT) and complementary to absolute temperature (CTAT) components in a bridge configuration, using bipolar transistors to generate a temperature-independent output, where the PTAT component serves as an internal reference and the CTAT component is trimmed to compensate for errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a band-gap voltage reference circuit is used to provide temperature compensation, then temperature stability is improved, but higher-order errors and process variations still affect accuracy
Solution Approach 1:
The voltage reference circuit is segmented into distinct functional blocks: a PTAT voltage generation block using bipolar transistors Q1-Q4 and resistors R1-R4, a CTAT voltage generation block using bipolar transistors Q5-Q6 and resistors R5-R6, and a summation block. This segmentation allows independent optimization and trimming of each block to compensate for process variations and higher-order errors.
Solution Approach 2:
The circuit utilizes parameter changes by summing voltages with opposite temperature coefficients (PTAT and CTAT) to achieve temperature independence. The PTAT voltage increases with temperature while the CTAT voltage decreases, and their sum remains stable. Additionally, trimming mechanisms allow adjustment of resistance values to compensate for process variations and higher-order errors.
2Manufacturing precision
If trimming circuits are added to compensate for higher-order errors, then accuracy is improved, but circuit complexity increases
Solution Approach 1:
The circuit incorporates trimming mechanisms that are configured to be adjusted at a single reference temperature during manufacturing. This preliminary action allows the circuit to be calibrated once to compensate for process variations and higher-order errors, eliminating the need for continuous or complex multi-point trimming operations during operation.
Solution Approach 2:
The PTAT voltage generation block serves as a self-referencing element that automatically compensates for its own process variations through the inherent properties of bipolar transistor base-emitter voltage differences. This self-service mechanism reduces the burden on external trimming circuits and simplifies the overall design.
3Manufacturing precision
If multiple trimming steps are used to achieve high accuracy, then manufacturing precision is improved, but productivity decreases
Solution Approach 1:
The circuit is designed to require only a single trimming step at a reference temperature during manufacturing, rather than multiple trimming steps at different temperatures or conditions. This preliminary calibration action significantly reduces manufacturing time and increases productivity while still achieving high accuracy through the combination of PTAT and CTAT voltage summation and the self-referencing PTAT block.
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 provides a voltage reference that is first-order temperature insensitive, achieving high precision and low noise with reduced variability due to process changes and mismatch, and can be trimmed at a single temperature for accuracy.
Implementation Method 1
The first voltage component is related to a base-emitter voltage of a bipolar transistor which inherently has a form which is Complementary To Absolute Temperature, denoted as a CTAT voltage. The second voltage component is obtained from the base-emitter voltage difference, ΔVBE, of two bipolar transistors operating at different collector current densities. This voltage is Proportional To Absolute Temperature and it is denoted a PTAT voltage.
Implementation Method 2
the present disclosure relates to a methodology and circuitry configured to provide an output signal that combines a proportional to absolute temperature component with a complimentary to absolute temperature component to generate a stable output which is not temperature dependent
Data Source
AI summary
The present disclosure relates to a method and apparatus for generating a voltage reference. More particularly the present disclosure relates to a methodology and circuitry configured to provide an output signal that combines a proportional to absolute temperature component with a complimentary to absolute temperature component to generate a stable output which is not temperature dependent.