| 摘要 |
Both buses connected to a bus switch are protected from undershoots. A bus switch transistor is an n-channel metal-oxide-semiconductor (MOS) with its source connected to a first bus and its drain connected to a second bus. An enable gate drives the gate node of the bus switch transistor high to enable or low to disable. Undershoot sensing circuits are attached to the first and second bus. When a low-going transition is detected by an undershoot sensing circuit, an n-channel connecting transistor is turned on, connecting the bus with the low-going transition to the gate node through a grounded-gate n-channel transistor. If an undershoot occurs, it is coupled to the gate node. Since both the gate and source of the bus switch transistor are coupled to the undershoot, the gate-to-source voltage never reaches the transistor threshold and the bus switch transistor remains off.
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