External Bandgap Reference Trimming for Lower Residual Error
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Solution Overview
Problem
Existing bandgap reference circuits in semiconductor devices face chip-to-chip variations due to manufacturing process variations, leading to inconsistencies in the bandgap voltage across devices.
Innovation Solution
The proposed solution involves trimming the voltage reference outside of the bandgap core using an auxiliary section with an auxiliary diode and trimming element, coupled to a current source and resistors, allowing for adjustment of the bias current to fine-tune the voltage reference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If trimming is performed within the bandgap core circuitry, then voltage reference accuracy can be adjusted, but residual errors increase and silicon area is consumed
Solution Approach 1:
The patent divides the trimming function into two separate segments: the bandgap core circuitry remains fixed and non-trimmable, while a standalone auxiliary section performs the trimming operation. This segmentation prevents residual errors by keeping trimming operations external to the core, thereby maintaining core accuracy while allowing voltage reference adjustment through the auxiliary section's trimmable resistors or current sources.
2Measurement precision
If trimming elements are integrated within the bandgap core, then voltage reference can be fine-tuned, but silicon area increases
Solution Approach 1:
The patent extracts the trimming elements from the bandgap core circuitry and places them in a separate auxiliary section. This extraction allows the core to remain compact and non-trimmable, while the auxiliary section contains all trimmable components such as resistors or current sources that adjust the voltage reference, thereby reducing overall silicon area consumption.
3Measurement precision
If traditional trimming processes are used within bandgap core, then voltage reference can be adjusted, but test time increases
Solution Approach 1:
The patent implements preliminary trimming action through the auxiliary section that operates independently of the bandgap core. The auxiliary section's trimmable elements (resistors or current sources) are pre-configured to adjust the voltage reference before final device operation, reducing the need for iterative testing and minimizing test time while maintaining adjustment capability.
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 ensures optimal core accuracy with minimal residual errors, reduces silicon area and test time, and is compatible with various bandgap reference circuits, including those with higher order base-emitter voltage curvature compensation.
Implementation Method 1
The set point of the trimming element is adjusted so as to inject a bias current into the auxiliary section
Implementation Method 2
Embodiments described herein control the bias current adjustment by changing a mirror ratio of the above-noted current source, e.g., a pair of field effect transistors such as first and second p-channel metal-oxide-semiconductors
Data Source
AI summary
An electrical circuit includes positive and negative voltage rails, a reference voltage rail, a non-trimmable bandgap core configured to output a voltage reference on the reference voltage rail, and a trimming element in an auxiliary section located external to the bandgap core. A current source is coupled to the non-trimmable bandgap core and the positive voltage rail. An auxiliary diode arranged in an auxiliary section outside of the bandgap core is coupled to the current source and negative voltage rail. The trimming element is coupled to the current source external to the non-trimmable bandgap core and has an adjustable set point. The adjustable set point is adjusted to inject a corresponding bias current to the auxiliary section during a trimming process and thereby change the voltage reference.