A printhead IC is provided having an ejection nozzle having a heater for heating printing fluid, and drive circuitry for generating print pulses and maintenance pulses for driving the heater of the ejection nozzle. The maintenance pulses have a series of sub-ejection pulses preceding a de-clog pulse. The print signals are generated to heat the heater to form a first vapor bubble in printing fluid that causes ejection of the printing fluid from the nozzle. The de-clog pulse is generated to have lower power and longer duration than the print pulses so as to heat the heaters to form a second vapor bubble in the printing fluid which does not cause ejection. The sub-ejection pulses are generated to have lower power than the print pulses and shorter duration than the de-clog pulse so as to heat the heater without sufficient energy to nucleate a vapor bubble in the printing fluid.