Bandgap Reference Circuit With Cascode PMOS for Wide Supply Range
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Solution Overview
Problem
Bandgap reference circuits face challenges in achieving high accuracy and stability over a wide range of operating conditions, particularly when operating at both high and low supply voltages, leading to issues such as voltage stress, system mismatch, and unsuitable use of advanced process technologies.
Innovation Solution
The bandgap reference circuit employs cascode structures in current sources to reduce voltage stress on PMOS transistors, uses amplifiers as source followers to mitigate system mismatch, and incorporates a temperature coefficient adjustment unit to stabilize the reference voltage, ensuring operation across varying power supply voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If protection measures are added to ensure safe operation at high voltages (1.5V), then the bandgap reference circuit can operate at higher voltages, but the circuit may not function properly at low voltages (0.9V)
Solution Approach 1:
The patent implements dynamic voltage range selection through a voltage range selection circuit that automatically switches between different operating modes based on the detected power supply voltage. This allows the bandgap reference circuit to adapt its internal configuration to match the current voltage range, ensuring reliable operation across both high (1.5V) and low (0.9V) voltage conditions without compromising functionality in either range.
2Reliability
If additional protection measures are implemented for high voltage operation, then the safe operating area is protected, but the circuit complexity increases
Solution Approach 1:
The patent divides the protection mechanism into segmented functional blocks: a voltage range detection unit that monitors the power supply voltage, a voltage range selection circuit that determines the appropriate operating mode, and a bandgap reference circuit that executes the selected mode. This segmentation allows protection functionality to be integrated without proportionally increasing overall circuit complexity, as each segment performs a specific function independently.
Data Source
AI summary
A bandgap reference circuit includes a first, a second and a third current source, a first and a second amplifier. The first, the second and the third current source each includes two cascode PMOS transistors for reducing the voltage stress applied to PMOS transistors when receives a high power supply voltage. The first amplifier controls the PMOS transistors in the first and the second current source to ensure that the PMOS transistors have enough headroom when receives a low power supply voltage. The second amplifier provides a gain-boosting loop to prevent the system mismatch of the PMOS transistors in the first, the second and the third current source. A temperature coefficient adjustment unit introduces positive temperature coefficients and negative temperature coefficients in the currents generated by the first and second current source, and a resistor generates the reference voltage according to a current duplicated by the third current source.