Capacitive Bias Bandgap Reference Circuit
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Solution Overview
Problem
Bandgap reference voltage circuits integrated onto semiconductor chips face limitations due to small current density ratios, making them sensitive to circuit non-idealities and device mismatch, which affects accuracy and stability, especially in modern technologies where integrating analog components is challenging.
Innovation Solution
The use of capacitive bias, where charged capacitors drive current densities through a P-N junction, allowing for large current density ratios by controlling discharge times, thereby generating a more accurate and stable reference voltage without relying on device matching or analog components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional current density ratio methods are used in bandgap reference circuits, then the circuit can operate with standard analog components, but the current density ratio is limited to one order of magnitude which reduces accuracy and increases sensitivity to circuit non-idealities
Solution Approach 1:
The patent replaces traditional analog current sources and device matching mechanisms with a digital-like capacitive timing system. By using capacitors to generate current densities through controlled discharge timing rather than analog component values, the system achieves higher precision current density ratios without relying on difficult-to-integrate analog components in modern semiconductor processes
Solution Approach 2:
The patent changes the fundamental parameter used to control current density from analog component characteristics (resistor values, transistor dimensions) to time-based capacitor discharge duration. This parameter transformation enables current density ratios of several orders of magnitude by simply adjusting timing intervals, dramatically improving reference voltage accuracy while avoiding analog integration challenges
2Measurement precision
If device matching is used to control current density ratio, then the circuit can maintain simplicity, but the achievable accuracy is limited by device mismatch
Solution Approach 1:
The patent substitutes device matching mechanisms with a timing-based capacitive system. Instead of relying on precise matching of MOS transistors or resistors, the system uses capacitor discharge timing to define current density ratios, eliminating sensitivity to device mismatch and achieving superior accuracy in modern semiconductor manufacturing
Solution Approach 2:
The patent uses identical capacitors for both current density generation, copying the same component design and characteristics. This approach eliminates the need for precise matching between different devices, as the same capacitor type is used throughout, and timing control provides the differentiation needed for various current density ratios
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 approach enables current density ratios of several orders of magnitude, resulting in a significantly more accurate and stable reference voltage, reducing sensitivity to circuit non-idealities and improving temperature compensation.
Implementation Method 1
The use of capacitive bias, where charged capacitors drive current densities through a P-N junction, allowing for large current density ratios by controlling discharge times
Implementation Method 2
first and second current densities through a P-N junction. The combination of P-N junction and capacitors operate in a region where each of their respective voltage decay behavior varies according to the natural log of time
Data Source
AI summary
An apparatus is described having a reference voltage circuit. The reference voltage circuit includes a diode to receive first and second currents having first and second respective current densities, where, the first and second current densities are different and determined by circuitry that precisely controls the respective amount of time the first and second currents flow into the diode. The reference voltage circuit also comprises circuitry to form a reference voltage by combining first and second voltages generated from respective voltages of the diode that result from the first and second currents flowing through the diode.