Low Voltage Bias Circuit for High Voltage Tolerance
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Solution Overview
Problem
Conventional self-biased reference circuits in integrated circuits face issues with variability in bias voltages due to manufacturing and operating conditions, lack of flexibility, and require large resistors and high voltage transistors, making them unsuitable for a wide range of power supply voltages and low current levels.
Innovation Solution
A bias protection circuit composed entirely of low voltage transistors, which generates a stable internal power supply voltage using a limit section, bias feedback section, and drive section, eliminating the need for large resistors and high voltage transistors, and allowing operation across a wide range of power supply voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional self-biased reference circuits are used, then reference voltage/current can be provided, but the circuit requires large resistors and high voltage transistors, increasing device complexity and reducing adaptability to different power supply voltages
Solution Approach 1:
The patent changes the operating parameters of the transistors by applying specific bias voltages (Vbias1, Vbias2, Vbias3, Vbias4) to operate the transistors in their saturation region, enabling the circuit to function with low voltage transistors instead of requiring high voltage transistors. This parameter change allows the reference circuit to maintain stability while reducing device complexity
Solution Approach 2:
The reference circuit is divided into distinct functional sections: a first section generating a first bias voltage, a second section generating a second bias voltage, and a third section generating the reference voltage. This segmentation allows each section to be optimized independently, using low voltage transistors in specific regions where high voltage transistors would otherwise be required, thereby reducing overall device complexity
2Adaptability or versatility
If high voltage transistors are used to accommodate wide power supply voltage range, then adaptability improves, but manufacturing complexity and cost increase
Solution Approach 1:
The patent applies different quality requirements to different parts of the circuit. Low voltage transistors are used in sections where high electric field tolerance is not critical, while the biasing network is designed to protect these low voltage transistors from high voltage conditions. This local differentiation allows the circuit to handle wide power supply voltage ranges without requiring all transistors to be high voltage devices, simplifying manufacturing
Solution Approach 2:
The patent introduces bias voltages (Vbias1, Vbias2, Vbias3, Vbias4) as intermediary control signals that mediate between the high voltage power supply and the low voltage transistors. These bias voltages act as intermediaries that protect the low voltage transistors from direct exposure to high voltage conditions, enabling the circuit to operate across wide voltage ranges using standard low voltage transistor processes
3Device complexity
If discrete voltage drop devices are used in non-biased reference circuits, then implementation is simple, but current consumption increases proportionally with supply voltage
Solution Approach 1:
The patent employs feedback mechanisms where the generated reference voltage is fed back to control the biasing of the transistor network. This feedback allows the circuit to automatically adjust its operating point to maintain low current consumption regardless of the supply voltage level, unlike discrete voltage drop devices where current is directly proportional to supply voltage. The feedback-controlled biasing ensures that current consumption remains low while maintaining reference accuracy
Data Source
AI summary
A circuit (200) can include a bias protection circuit (204) and a reference circuit (202). A bias protection circuit (204) can generate an internal power supply voltage (Vsuppi) from a higher device power supply (Vcch) with low voltage transistors and no resistors. A lower internal power supply voltage (Vsuppi) can be provided by buffer transistors (M5 and M6) that are biased according to limit section (206) that generates a bias voltage (biasn2) based on a threshold voltage drop and a feedback bias voltage (biasn1) from reference circuit (202).