Patent ID: 7891748

Claim:
A print engine controller for an inkjet printhead with a plurality of nozzle arrangements operatively actuated by thermal actuators, said controller having controller circuitry with an open actuator test circuit to test each respective actuator, the controller circuitry comprising: an open actuator test input, a column enable input and a row enable input; a drive transistor operatively linking said thermal actuator to a power supply; a bleed transistor arranged in parallel with the thermal actuator; a sensing node linking an output of the drive transistor and inputs of the thermal actuator and bleed transistor; and a sense transistor with a source connected to the sensing node, a drain connected to a sense output, and a gate connected to the open actuator test input; wherein during use, when only the column enable and row enable inputs are activated the bleed and sense transistors are deactivated and the drive transistor is activated to link the thermal actuator to the power supply, and when only the open actuator test input is activated the bleed and sense transistors are activated so that the thermal actuator is short-circuited and the sensing node is pulled high if the thermal actuator is open-circuit.