Patent ID: 7427887
Filing Date: 2008-09-23
Classification: H03K

Abstract:
1. An open drain driver comprising: a first transistor having a source, a drain coupled to an output node of the driver, and a gate coupled to a bias voltage node for receiving a bias voltage for maintaining the first transistor in a conducting state while the difference between the voltages on the gate and the source thereof is greater than or equal to the threshold voltage of the first transistor, a second transistor having a drain coupled to the source of the first transistor through a coupling node, a source coupled to a switching voltage node for receiving a switching voltage, and a gate coupled to a control node for receiving a control signal for operating the second transistor selectively and alternately in a non-conducting state for maintaining the output node in a high impedance state, and a conducting state for applying the switching voltage on the switching voltage node to the output node when the first transistor is in the conducting state, and a coupling element coupling the coupling node to a reference voltage node for receiving a reference voltage for limiting the voltage on the coupling node when the second transistor is in the non-conducting state, so that the drain-source voltage applied to the second transistor is within the reliability limit of the second transistor, the coupling element comprising a DC coupling element for DC coupling the coupling node to the reference voltage node, and a capacitive coupling element in parallel with the DC coupling element for capacitively coupling the coupling node to the reference voltage node.