Voltage-Mode Band-Gap Reference Circuit Trimming
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Solution Overview
Problem
Voltage-mode band-gap reference circuits face challenges in generating an output voltage near or below the 'magic' voltage, which is difficult to trim and requires a high supply voltage, and introduces noise that is hard to filter, making it difficult to meet temperature drift specifications in various applications.
Innovation Solution
A monolithic voltage reference circuit incorporating a voltage-mode band-gap reference circuit with temperature independent and dependent differential current sources, allowing for incremental trim settings to adjust the output voltage and temperature drift, using potentiometers and R2R resistor ladders to operate efficiently with a supply voltage not substantially larger than the magic voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a second stage is used to generate the output voltage, then the output voltage can be adjusted, but noise is introduced which is difficult to filter
Solution Approach 1:
The patent extracts the trimming function from a separate second stage and integrates it directly into the band-gap reference core circuit. By placing the trimming circuitry within the core reference voltage generation stage rather than adding it as a separate output stage, the design achieves output voltage adjustment capability while avoiding the noise generation that would occur in a separate amplification stage.
2Reliability
If the supply voltage is made much higher than the magic voltage, then the circuit can operate with adequate headroom, but the high supply voltage may be unavailable in certain applications
Solution Approach 1:
The patent changes the operating parameters of the band-gap reference circuit by implementing trimming mechanisms that allow the circuit to maintain stable operation with a supply voltage closer to the magic voltage. Through adjusting the reference voltage and compensation parameters via trimming circuits, the design achieves reliable operation with reduced supply voltage headroom requirements.
3Measurement precision
If traditional trimming methods are used, then the output voltage can be adjusted, but the process is difficult and time consuming
Solution Approach 1:
The patent segments the trimming function into independent, modular trimming circuits that can be individually adjusted. By dividing the trimming task into separate controllable elements (such as independent current source trimmers and voltage reference trimmers), the design enables systematic and efficient trimming procedures that reduce the time and complexity compared to traditional monolithic trimming approaches.
Solution Approach 2:
The patent implements preliminary trimming configurations during the circuit design and fabrication stage, establishing initial trim settings that reduce the amount of post-fabrication adjustment needed. By pre-configuring the trimming circuitry with default optimal settings, the final trimming process becomes faster and less complex, as only minor adjustments are required rather than complete calibration.
Data Source
AI summary
A monolithic voltage reference circuit may include a voltage-mode band-gap reference circuit, a temperature independent differential current source, and a temperature dependent differential current source. The voltage-mode band-gap reference circuit may include an error amplifier having differential input nodes. The temperature independent differential current source may be configured to add in or subtract from the differential input nodes a substantially temperature independent differential current with an allocation between the nodes that is controlled by a selectable output voltage trim setting. The temperature dependent differential current source may be configured to add in or subtract from the differential input nodes a substantially temperature dependent differential current with an allocation between the nodes that is controlled by a selectable temperature drift trim setting.