Patent ID: 6052019
Filing Date: 2000-04-18
Classification: H03K

Abstract:
An undershoot-protected bus switch comprising:an input;an output;an enable signal for indicating when the bus switch is in an isolation mode when the input is isolated from the output and for indicating a connection mode when the bus switch conducts current between the input and the output;a bus-switch transistor, coupled to connect the input to the output during connection mode, but to isolate the input from the output during isolation mode, the bus-switch transistor being controlled by a gate connected to a gate node;a connecting transistor, coupled to conduct from the input to the gate node during an undershoot below ground on the input;a pulse generator, coupled to the input, for generating a pulse in response to a transition of the input during the isolation mode;an enabling transistor, controlled by the enable signal, for driving an enabling voltage onto the gate node during the connection mode;a disabling transistor, controlled by the enable signal, for driving a disabling voltage onto the gate node during the isolation mode; andan isolating transistor, coupled between the disabling transistor and the gate node, the isolating transistor isolating the disabling transistor from the gate node in response to the pulse from the pulse generator,whereby the disabling transistor is isolated by the pulse while the gate node is driven by the undershoot through the connecting transistor.