Bootstrapped Switch Circuit for Gate-Induced Drain Leakage Control
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Solution Overview
Problem
Gate-induced drain leakage (GIDL) occurs in transistors due to high electric fields at the gate drain overlap, particularly in thin oxide technologies, leading to significant leakage currents and increased ON resistance in circuits, especially in bootstrapped switches.
Innovation Solution
A GIDL protection circuit is implemented, comprising a switch protection circuit that maintains a drain voltage less than a supply voltage in the OFF state and a ground protection circuit that maintains a drain voltage less than the supply voltage in the ON state, using a configuration of transistors and capacitors to limit voltage differences and prevent excessive leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If thin oxide transistors are used to scale down device size, then device integration density is improved, but gate-induced drain leakage increases significantly
Solution Approach 1:
The patent introduces a protection circuit as an intermediary component between the thin oxide transistor and the output node. This protection circuit includes a first protection transistor connected to the gate and drain of the main transistor, and a second protection transistor connected to ground. The intermediary protection circuit clamps the voltage differential across the main transistor to prevent GIDL while allowing the thin oxide transistor to maintain its high integration density benefits.
2Speed
If high internal voltages are used in bootstrapped switches, then switching performance is improved, but susceptibility to GIDL increases
Solution Approach 1:
The protection circuit applies preliminary anti-action by preemptively clamping the voltage differential across the bootstrapped switch transistor before GIDL can occur. The first protection transistor is configured to activate when the voltage differential exceeds a threshold, preventing the high electric field conditions that would cause GIDL. This allows the bootstrapped switch to operate with high internal voltages for improved switching performance while the protection circuit prevents the harmful GIDL effect.
3Device complexity
If GIDL is not addressed in OFF state, then circuit simplicity is maintained, but leakage current increases and loads output circuitry
Solution Approach 1:
The protection circuit is designed to be self-activating based on the voltage conditions across the main transistor. The first protection transistor automatically turns on when the voltage differential exceeds the threshold, providing GIDL protection without requiring external control signals or complex control logic. The second protection transistor similarly self-activates to clamp the drain voltage to ground potential. This self-service mechanism provides effective GIDL protection while adding minimal complexity to the circuit.
4Device complexity
If GIDL is not addressed in ON state, then device complexity is reduced, but ON resistance increases dramatically
Solution Approach 1:
The second protection transistor acts as an intermediary to ground that activates during the ON state to prevent GIDL. When the bootstrapped switch is ON and the gate voltage is high, the second protection transistor clamps the drain voltage to ground potential, preventing the high electric field at the drain-gate overlap region. This intermediary protection mechanism maintains low ON resistance by preventing GIDL-induced leakage paths while adding minimal complexity to the overall device structure.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The GIDL protection circuit effectively reduces leakage currents and maintains reliable operation by keeping drain voltages within safe limits, thereby minimizing ON resistance and preventing voltage droop in bootstrapped circuits.
Implementation Method 1
GIDL occurs due to band-to-band tunneling as a direct result of high electric fields generated at the gate drain overlap when a device (e.g., a transistor) is in an OFF state
Data Source
AI summary
Examples described herein provide an apparatus having a circuit with a grounding circuit and a switch. The apparatus generally includes a gate induced drain leakage (GIDL) protection circuit coupled to the switch and to an output voltage. The GIDL protection circuit may include a switch protection circuit configured to maintain a drain voltage of the switch less than a first supply voltage (Vdd) when the circuit is in an OFF state; and a ground protection circuit configured to maintain a drain voltage of the grounding circuit less than the first supply voltage when the circuit is in an ON state.