Bandgap Voltage Calibration Using Resistor Ladder Trimming
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Solution Overview
Problem
Bandgap circuits in integrated circuits face inaccuracies due to variations in transistor threshold voltages, resistor ratios, and geometrical parameters, leading to unstable reference voltages that cause operation errors.
Innovation Solution
A bandgap circuit with a core that generates temperature-independent voltage, integrated with a resistor ladder for voltage scaling and an output switch for calibration, along with a current mirror for proportional to absolute temperature (PTAT) current, minimizes variations by calibrating the output voltage to a desired level, making it independent of process, power supply, and temperature variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If bandgap circuit is used to generate reference voltage, then temperature independence is achieved, but process variations cause voltage level inaccuracies
Solution Approach 1:
The patent performs voltage calibration during a preliminary testing phase before final product shipment. Test circuits measure the actual output voltage of the bandgap circuit and store calibration data in non-volatile memory. During normal operation, this pre-stored calibration data is used to compensate for process variations, achieving accurate voltage levels without requiring post-manufacturing adjustments.
Solution Approach 2:
The bandgap circuit includes self-calibration functionality where the circuit uses its own output voltage to perform calibration measurements. The test circuitry within the bandgap module measures its own voltage levels and automatically stores calibration parameters, enabling the circuit to self-adjust for process variations without external intervention during operation.
2Manufacturing precision
If external voltage references are used, then voltage accuracy is improved, but power consumption and noise increase
Solution Approach 1:
The patent integrates the voltage reference functionality directly into the bandgap circuit module, combining the temperature-compensating bandgap core with calibration circuits and non-volatile memory in a single integrated structure. This eliminates the need for separate external voltage reference components, reducing overall power consumption and noise while maintaining voltage accuracy through the integrated calibration mechanism.
Data Source
AI summary
A bandgap circuit generates a substantially constant output voltage. The bandgap circuit can be integrated with other circuits of an integrated circuit and its absolute output voltage value can be calibrated to a desired voltage level. As such, the variation in absolute voltage levels which may be caused by variation in devices' parameters subject to different fabrication processes is minimized or substantially eliminated. The bandgap circuit includes a bandgap core that generates a temperature independent voltage. The bandgap circuit also includes a resistor ladder that is coupled in parallel to the bandgap core and scales the temperature independent voltage into voltage levels proportional to the temperature independent voltage. An output switch of the bandgap circuit selects the voltage level on the resistor ladder that is substantially equal to a desired voltage level. The bandgap circuit also includes a current mirror that outputs a proportional to absolute temperature current.