Semiconductor memory device having self-refresh and back-bias circuitry

A back-bias generator in a semiconductor memory device having memory self-refresh operation, comprising:

• means for receiving a self-refresh enable signal;
• means for receiving a back-bias control clock pulse from a back-bias clock generating circuit, said back-bias control clock pulse providing a steady back-bias oscillating frequency during a memory self-refresh operation;
• charge pump means coupled to an oscillator and a back-bias voltage detection circuit for generating a back-bias voltage;
• selection means for receiving an output from said back-bias voltage detection circuit and selectively transmitting an input signal to said oscillator in response to said self-refresh enable signal;
• and
• driver control means connected to said charge pump means for gating an output from said oscillator and the back-bias control clock pulse from said back-bias clock generating circuit.

A semiconductor memory device comprising:

• means for generating a refresh clock pulse;
• counter means for generating a predetermined number of signals of different frequency in response to said refresh clock pulse;
• means for generating a self-refresh enable signal in response to said predetermined number of signals from said counter means;
• means for generating a back-bias control clock pulse comprising first, second and third selector circuits, said third selector circuit selecting one of said predetermined number of signals transmitted from said counter means in response to an output from each of said first and second selector circuits;
• means for generating a back-bias voltage including an oscillator circuit and a back-bias voltage detection circuit;
• selection means for receiving an output from said back-bias voltage detection circuit and selectively transmitting a signal to said oscillator circuit in response to said self-refresh enable signal;
• and
• driver control means for receiving an output from said oscillator circuit and said back-bias control clock pulse.