Output driver circuit with jump start for current sink on demand

摘要

An output driver circuit for coupling a logic circuit to load includes an input node, an output node for coupling to the load and a pull down switch which discharges the output node in response to a signal received at the input node. A current sink circuit includes a feeder transistor which provides current to the control terminal of the pull down switch to render the pull down switch conductive when the voltage at the output node exceeds a first threshold value between a logic high and a logic low. The feeder transistor is charged by a first charging path having a first impedance by which it takes a first time period to render the pull down switch conductive, the first impedance providing a low standby current when the voltage at the output node is below about the first value. A jump start circuit having a second current path with a lower impedance than the first current path charges the control terminal of the feeder transistor to said threshold faster than said first path and is disabled when the voltage at the output node falls below about the first value, thereby saving power.