Auto-calibrated Bandgap Reference Circuit with Dual-Mode Calibration
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Solution Overview
Problem
Bandgap reference circuits face challenges in generating accurate reference voltages due to input offset voltage variations, leading to high operating current and noise, and require costly calibration sequences and non-volatile memory or fuses during manufacturing.
Innovation Solution
A dual-mode voltage reference generator that automatically calibrates in-system upon power-on, using a chopper-stabilized bandgap reference circuit with modulated and un-modulated feedback modes, and an adjustable register-controlled resistor to compensate for voltage differences, eliminating the need for high-speed clocks and costly calibration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If chopper-stabilized bandgap reference circuit with high-speed clock is used, then input offset voltage errors are reduced, but operating current and noise increase
Solution Approach 1:
The patent implements periodic calibration action by using a calibration mode that is activated intermittently rather than continuously. The bandgap reference circuit operates in normal mode during most time, and switches to calibration mode periodically to adjust trimming registers, thereby reducing average power consumption while maintaining accuracy.
Solution Approach 2:
The patent extracts the calibration function from continuous operation and separates it into a distinct periodic calibration mode. By taking out the high-current chopper-stabilized operation from continuous use and limiting it to periodic calibration events, the circuit achieves low power consumption during normal operation while still obtaining accuracy benefits when needed.
2Measurement precision
If chopper-stabilized bandgap reference circuit with high-speed clock is used, then input offset voltage errors are reduced, but noise increases
Solution Approach 1:
The high-speed clock and chopper-stabilized operation are activated only periodically during calibration events rather than continuously. This periodic activation reduces the overall noise floor in the circuit while maintaining the ability to correct offset voltage errors when calibration is performed.
Solution Approach 2:
The patent uses volatile trimming registers that are recalibrated periodically rather than maintaining continuous high-precision operation. The calibration data is temporarily stored in volatile memory and refreshed periodically, accepting occasional recalibration in exchange for reduced continuous noise and power consumption.
3Measurement precision
If calibration or trimming techniques during wafer sort or final test are used, then reference voltage accuracy is improved, but manufacturing cost and testing time increase
Solution Approach 1:
The bandgap reference circuit performs self-calibration automatically using on-chip trimming registers and calibration logic. The circuit monitors its own performance and adjusts its own trimming parameters without requiring external calibration equipment or manual intervention during manufacturing, thereby reducing manufacturing cost and testing time.
Solution Approach 2:
The circuit includes preliminary calibration capability that can be performed during manufacturing test, but the real innovation is the ability to perform additional calibration in-field if needed. The trimming registers are prepared in advance during manufacturing, but the circuit can self-adjust later without external help, reducing the stringency of manufacturing calibration requirements.
4Measurement precision
If calibration or trimming techniques during wafer sort or final test are used, then reference voltage accuracy is improved, but testing time increases
Solution Approach 1:
The circuit performs self-calibration using integrated trimming registers and calibration logic, eliminating the need for lengthy external calibration procedures during manufacturing. The self-service calibration capability reduces testing time by allowing rapid automated adjustment without external calibration equipment.
Solution Approach 2:
The circuit is designed with preliminary trimming registers that can be quickly programmed during manufacturing test, and with the additional capability to perform further calibration in-field if needed. This preliminary preparation reduces the time required during manufacturing while maintaining flexibility for future calibration if required.
Data Source
AI summary
A voltage reference generator which can be automatically calibrated has a first mode and a second mode. The voltage reference generator provides a bandgap reference voltage with a voltage reference node having a capacitance. Calibration logic, which can be on the same integrated circuit device as the voltage reference generator, executes a calibration sequence including enabling the voltage reference generator in the first mode to produce a voltage on the voltage reference node, holding the voltage by the capacitance, and then enabling the voltage reference generator in the second mode and calibrating the voltage reference generator in the second mode relative to the voltage held on the voltage reference node, to provide the bandgap reference voltage.