US Patent 7560977 Step-up booster circuit

In a step-up booster circuit, a number of pump circuits are connected in series. Pump control signals are outputted from a pump control circuit, and the pump circuits accordingly generate a required raised voltage by stepping up voltages of signals inputted to the respective pump circuits. The step-up circuit includes an activation control circuit which generates a pump activation signal in accordance with provided signals, which direct operation of the step-up circuit. The pump control circuit controls output of the pump control signals in accordance with a voltage of the pump activation signal.