Patent ID: 6781415
Filing Date: 2004-08-24
Classification: H03K

Abstract:
An active bi-directional voltage level translation switch joining a higher voltage signal first node to a lower voltage signal second node, the translation switch comprising:an NMOS switch device with a drain connected to the first node, a source to the second node, and a gate to a control node, an enable signal, a control circuit with an input connected to the enable signal and an output connected to the control node, wherein the enable signal defines two states, a switch on state and a switch off state, a reference voltage connected to the control circuit, wherein, in the switch on state, the reference voltage supply is applied to the control node and clamps the source to a voltage that is compatible with the lower voltage signal, and wherein, in the switch off state, a voltage signal is applied to the control node that turns off the translation switch, a pull up circuit connected from the first node to the higher voltage, the pull up circuit defining a threshold that is lower than the lower voltage, wherein when the drain voltage is higher than the threshold the pull up circuit drives the first node toward the higher voltage, and when the drain voltage is lower than the threshold voltage the pull up circuit is disabled, and when the translation switch is on and a lower voltage circuit drives the first node low via the translation switch, the lower voltage drive circuit overcomes the pull up circuit.