Bandgap Reference Circuit Layout for High-Temperature Leakage Compensation
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Solution Overview
Problem
Bandgap-type voltage reference circuits experience leakage current issues at high temperatures, affecting the temperature characteristic of the voltage output, leading to increased current through the substrate and undesirable voltage characteristics.
Innovation Solution
The integration of a voltage reference circuit with a parallel configuration of current sources, diode-connected bipolar transistors, and resistors, along with a control circuit that adjusts the number of bipolar transistors and resistors to compensate for leakage currents, ensures a stable reference voltage with a desired temperature characteristic.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a bandgap-type voltage reference circuit is used, then a stable reference voltage can be obtained, but leakage current occurs at high temperatures which degrades the temperature characteristic of the voltage output
Solution Approach 1:
The voltage reference circuit is divided into multiple independent branches, each containing a bipolar transistor with its own leakage current path. By segmenting the circuit, the total leakage current is distributed across multiple paths rather than concentrating through a single path, thereby reducing the impact of leakage on the overall reference voltage stability at high temperatures.
Solution Approach 2:
The circuit employs transistors with different current gain parameters (β values) to create branches with different leakage characteristics. By carefully selecting and combining transistors with varying parameters, the design achieves compensation where the leakage currents of individual branches offset each other, maintaining stable reference voltage output across temperature variations.
2Stability of the object's composition
If the number of bipolar transistors is increased to improve voltage stability, then the reference voltage becomes more stable, but the circuit complexity and manufacturing difficulty increase
Solution Approach 1:
The voltage reference circuit is divided into multiple independent branches, each containing a bipolar transistor with its own leakage current path. By segmenting the circuit, the total leakage current is distributed across multiple paths rather than concentrating through a single path, thereby reducing the impact of leakage on the overall reference voltage stability at high temperatures.
Solution Approach 2:
Multiple voltage reference branches are combined in parallel to achieve both stability and leakage compensation. The merging of multiple branches with different characteristics creates a composite reference voltage that benefits from both the stability of individual references and the leakage compensation effect, without requiring excessive complexity in any single branch.
Data Source
AI summary
An integrated circuit, including: a first current source; a second current source provided in parallel to the first current source; a first resistor with one end coupled to an output of the first current source; a first bipolar transistor that is diode-connected and is coupled to the other end of the first resistor; a second bipolar transistor that is diode-connected and is coupled to an output of the second current source; a second resistor coupled to the second bipolar transistor; and an output circuit configured to output a voltage based on a first voltage outputted from the first current source and a second voltage outputted from the second current source.