Ratiometric Current Source Circuit With Reduced Temperature Drift
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current current source circuits in computer systems are susceptible to temperature and supply voltage variations, leading to errors in circuit operation, particularly in analog-to-digital conversion and clock signal generation, due to their inherent dependence on these factors.
Innovation Solution
A current source circuit design that utilizes a first and second divider circuit with resistors having the same sign temperature coefficients, combined with a buffer circuit, to generate a current that is proportional to the supply voltage and reduced in temperature dependence, allowing for a frequency control signal in oscillator subsystems with minimal temperature and supply voltage influence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a traditional current source circuit is used, then the circuit provides current output, but the current is highly dependent on temperature and supply voltage variations
Solution Approach 1:
The patent changes the temperature coefficient parameter of the resistors from opposite signs (traditional bandgap) to the same sign. By using resistors with matching temperature coefficients in the divider circuits, the temperature-dependent variations in the current output are minimized, as both resistors in each divider track temperature changes similarly, maintaining a stable current ratio.
2Reliability
If a bandgap reference circuit is used to reduce temperature dependence, then current stability improves, but circuit complexity increases
Solution Approach 1:
The patent extracts and eliminates the complex bandgap reference circuitry from the design. Instead of using the traditional bandgap approach with its multiple transistors, resistors, and carefully controlled voltage drops, the invention simplifies the circuit to basic divider circuits with resistors having the same sign temperature coefficients, achieving temperature compensation without the complexity of bandgap reference implementation.
3Reliability
If resistors with opposite sign temperature coefficients are used (traditional approach), then temperature compensation is achieved, but manufacturing precision requirements increase
Solution Approach 1:
The patent applies homogeneity by using resistors with the same sign temperature coefficients throughout the divider circuits. This homogeneous approach means all resistors respond similarly to temperature changes, and by designing the divider ratios appropriately, the temperature effects cancel out. This is more manufacturable than opposite sign coefficients because it relies on matching resistors of the same type rather than precisely matching resistors with fundamentally different temperature behaviors.
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 current source circuit with reduced temperature and supply voltage dependence, enhancing the stability of clock signals and reducing errors in circuit operations, while simplifying the design compared to traditional bandgap reference circuits.
Implementation Method 1
The second divider circuit includes a first resistor with a first temperature coefficient and a second resistor with a second temperature coefficient
Data Source
AI summary
A ratiometric current source circuit having a reduced temperature dependence is disclosed. An embodiment of the current source circuit includes a first divider circuit configured to generate a reference voltage using a voltage level of a power supply node and a second divider circuit including a first resistor with a first temperature coefficient and a second resistor with a second temperature coefficient. The first resistor is configured to generate a first current using an input voltage and the voltage level of the power supply node and the second resistor is configured to generate a second current using the input voltage. The embodiment further includes a buffer circuit configured to generate the input voltage using the reference voltage and generate an output current using a difference between the first current and the second current.