Voltage Regulator Output Stage Using Stacked Transistors
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Solution Overview
Problem
Existing voltage regulators that use middle voltage devices are limited in output voltage range when operating in high voltage domains, as the cross voltage of output transistors may exceed their withstand voltage, necessitating the use of high voltage devices to prevent overstress.
Innovation Solution
Incorporating a stack transistor between the output transistor and the output terminal of the voltage regulator, coupled with a voltage generator to provide a proper gate control voltage, allowing the output stage circuit to operate with middle voltage devices while preventing overstress by clamping the drain-to-source voltage within the transistor's withstand limits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If high voltage devices are used in the output stage, then the output voltage range can cover high voltage domains, but the chip area and circuit costs increase
Solution Approach 1:
The output stage is segmented into multiple transistor stages (first output transistor, second output transistor, third output transistor) connected in series. This segmentation allows each transistor to handle a portion of the total voltage, enabling the use of middle voltage devices instead of high voltage devices while achieving high voltage domain operation.
Solution Approach 2:
Middle voltage devices are used as intermediary components between the control circuit and the high voltage power supply. The stacked transistor configuration acts as an intermediary structure that distributes voltage stress across multiple devices, allowing the system to operate in high voltage domains without requiring individual high voltage transistors.
2Area of stationary object
If middle voltage devices are used in the output stage, then chip area and circuit costs are reduced, but the output voltage range is limited and cross voltage may exceed withstand voltage
Solution Approach 1:
The output voltage is segmented across multiple middle voltage transistors connected in series. By dividing the total voltage burden among three or more transistors, each transistor experiences only a fraction of the total voltage, keeping the drain-to-source voltage within the withstand voltage limits of middle voltage devices while enabling high voltage domain operation.
Solution Approach 2:
The circuit changes the voltage distribution parameters by introducing intermediate voltage nodes between the transistors. This parameter change allows the system to operate with middle voltage devices by ensuring that no single transistor experiences voltage exceeding its withstand capability, while the overall system achieves high voltage domain coverage.
3Device complexity
If middle voltage devices are used without voltage distribution, then circuit complexity is reduced, but the drain-to-source voltage exceeds transistor withstand voltage causing overstress
Solution Approach 1:
The output stage is segmented into multiple transistor stages with intermediate nodes, which naturally distributes the voltage stress. This segmentation provides inherent voltage protection without requiring complex control circuits, maintaining relatively simple circuit architecture while ensuring transistor safety through passive voltage distribution.
Solution Approach 2:
The stacked transistor configuration provides beforehand cushioning by distributing voltage stress across multiple devices before any single transistor can experience overstress. This passive protection mechanism prevents voltage spikes or transient conditions from exceeding the withstand voltage of individual middle voltage transistors.
Data Source
AI summary
An output stage circuit of a voltage regulator includes a first output transistor, a first voltage generator and a first stack transistor. The first stack transistor is coupled between the first output transistor and an output terminal of the voltage regulator, and includes a first terminal, a second terminal and a third terminal. The first terminal is coupled to the output terminal of the voltage regulator. The second terminal is coupled to the first output transistor. The third terminal is coupled to the first voltage generator.