Bootstrapping Switch Gate Protection Against Voltage Overstress
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Solution Overview
Problem
Conventional bootstrapping switches in communication devices often result in premature device aging and failure due to voltage overstress, leading to issues like hot carrier injection and dielectric breakdown, especially when handling high input voltages.
Innovation Solution
The implementation of a bootstrapping switch with a diode-connected MOS transistor in the pull-down path, coupled with additional protection transistors, ensures that the gate terminal is protected from excessive voltages, allowing for reliable switching without performance degradation, by using a capacitor to switch the MOS transistor between ON and OFF states and utilizing NMOS transistors integrated on a CMOS chip.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional bootstrapping switches are used to handle high input voltages, then switching capability is improved, but device reliability deteriorates due to voltage overstress causing hot carrier injection and dielectric breakdown
Solution Approach 1:
A diode-connected MOS transistor is introduced as an intermediary protective element in the pull-down path. This intermediary component limits the maximum voltage that can appear at the gate terminal of the switching MOS transistor, thereby preventing voltage overstress while maintaining the switch's ability to handle high input voltages through the bootstrapping mechanism
2Device complexity
If bootstrapping switches operate without voltage protection, then circuit simplicity is maintained, but device lifespan deteriorates due to premature aging and failure
Solution Approach 1:
The pull-down path is segmented into multiple functional sections: a diode-connected MOS transistor for voltage limiting, and additional protection transistors for enhanced gate terminal protection. This segmentation allows each component to perform a specific protective function, extending device lifespan while adding minimal complexity to the overall circuit
Data Source
AI summary
Methods and systems for reliable bootstrapping switches may comprise sampling a received signal with a bootstrapping switch, where the bootstrapping switch comprises a switching metal-oxide semiconductor (MOS) transistor having a pull-down path coupled to a gate terminal of the switching MOS transistor, wherein: source terminals of both a diode-connected transistor and a second MOS transistor are coupled to the gate terminal of the switching MOS transistor; drain terminals of both the diode-connected transistor and the second MOS transistor are coupled to a source terminal of a third MOS transistor, the third MOS transistor coupled in series with a fourth MOS transistor; and a drain terminal of the fourth MOS transistor is coupled to ground. The third and fourth MOS transistors may be in series with the second MOS transistor. A gate terminal of the fourth transistor may be switched from ground to a supply voltage to activate the pull-down path.