Patent ID: 6075400
Filing Date: 2000-06-13
Classification: H03K

Abstract:
A charge-canceling bus switch comprising:a first input;a second input;a control input for indicating when the bus switch connects the first input to the second input, and for indicating when the bus switch isolates the first input from the second input;a p-channel main transistor having a conducting channel selectively coupling the first input to the second input in response to the control input, the p-channel main transistor injecting a first charge into the first input in response to a transition of the control input;an n-channel main transistor having a conducting channel selectively coupling the first input to the second input in response to the control input, the n-channel main transistor injecting a second charge into the first input in response to a transition of the control input;a first compensating capacitor, coupled to the first input, for injecting a compensating charge into the first input in response to a transition of the control input;second compensating capacitor, coupled to the second input, for injecting a second compensating charge into the second input in response to a transition of the control input;a connecting transistor, coupled between the first input and the second input, for connecting the first input to the second input before the p-channel main transistor connects the first input to the second input during the transition when the transition of the control input connects the first input to the second input; andcross-coupled delay means, coupled to the control input, for generating a first signal to a gate of the p-channel main transistor and a second signal to a gate of the n-channel main transistor;wherein a delay from the control input to the first signal is substantially equal to a delay from the control input to the second signal for a transition of the control input,whereby the compensating charge compensates for a difference between the first charge and the second charge to reduce a net charge injected into the first input when the transition of the control input occurs.