Output buffer having sequentially-switched output
AssigneeU.S. Philips Corporation
InventorRichard C. Foss
Life of this patent
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Abstract
An integrated semiconductor circuit includes an output stage and a control circuit. The output stage comprises several (e.g. four) pull-down output transistors, which are sequentially switched on for pulling down the output node, whereby four small current steps are made instead of one high current step. As a result the package inductance generated power supply line noise will be substantially reduced (by at least a factor four). The same technique can be used for limiting the supply line noise due to the charge current for charging the output node via pull-up transistors.
Claims14
An integrated semiconductor circuit comprising a control circuit, an output stage, an input and an output, the output stage comprising pull-up means connected between a first supply terminal and the output and pull-down means connected between a second supply terminal and the output, said control circuit controlling at least one of said pull-up and pull-down means for limiting the time rate of change of current at the output upon receiving an input signal change at the input, at least one of said pull-up and pull-down means comprising at least two semiconductor devices each having a control electrode and first and second main electrodes, the semiconductor devices being connected in parallel except for their control electrodes, said control electrodes receiving control signals from the control circuit for sequentially changing the state of said semiconductor devices upon receiving a change of the input signal.
Dependencies are inferred from the claim text.