Bandgap reference circuit and semiconductor device
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Solution Overview
Problem
Existing bandgap reference circuits suffer from characteristic variation among manufactured units due to variations in the diode characteristic elements used, affecting the temperature characteristics of the reference voltage.
Innovation Solution
A bandgap reference circuit is designed with a diode characteristic element group, a dynamic element matching circuit, a reference voltage generation circuit, and a second-order temperature coefficient adjustment circuit. The dynamic element matching circuit repeatedly selects different combinations of diode characteristic elements to average their characteristics, while the second-order temperature coefficient adjustment circuit adjusts the temperature coefficients of the reference voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a reference voltage generating circuit uses diode characteristic elements with different current densities to generate reference voltage, then temperature characteristics are improved, but characteristic variation occurs among manufactured units due to manufacturing variation
Solution Approach 1:
The circuit divides the diode characteristic elements into multiple groups (first diode characteristic element group and second diode characteristic element group) with different current densities. By segmenting the elements and using dynamic element matching to selectively combine them, the circuit achieves both temperature compensation and reduced manufacturing variation. The segmentation allows independent optimization of each group's characteristics while maintaining overall stability.
Solution Approach 2:
The patent employs dynamic element matching that repeatedly changes the combination of diode characteristic elements selected from the groups over time. This dynamic selection process averages out manufacturing variations across multiple measurements, thereby reducing characteristic variation while maintaining the temperature compensation benefits of having multiple groups with different current densities.
2Manufacturing precision
If multiple diode characteristic elements are used to reduce characteristic variation, then manufacturing precision is improved, but device complexity increases
Solution Approach 1:
The patent merges multiple diode characteristic elements into parallel groups (first group and second group) that can be dynamically selected. By combining elements in parallel within groups and using dynamic matching to select between groups, the circuit reduces characteristic variation without requiring completely separate measurement paths, thereby controlling complexity while achieving precision.
Solution Approach 2:
The dynamic element matching circuit repeatedly and periodically changes the combination of diode characteristic elements selected from the groups. This periodic switching allows the circuit to average out manufacturing variations over time while using a relatively simple structure that alternates between predefined groups, rather than requiring complex continuous adjustment mechanisms.
Data Source
AI summary
A bandgap reference circuit includes: a diode characteristic element group; a dynamic element matching circuit that repeats, within a predetermined period, an operation of selecting, from the diode characteristic element group, a first diode characteristic element group including M diode characteristic elements connected in parallel and a second diode characteristic element group including N (≥M) diode characteristic elements connected in parallel, while changing a combination of the diode characteristic elements to be selected; a reference voltage generation circuit that generates a reference voltage based on a difference between a current density of current passing through the first diode characteristic element group and a current density of current passing through the second diode characteristic element group; and a second-order temperature coefficient adjustment circuit that adjusts a second-order temperature coefficient of the reference voltage generated.