| 摘要 |
An oscillator for outputting an oscillation signal with a period changing as a step function in inverse proportion to temperature is provided to change a refresh period of a memory cell properly to the characteristics of the memory cell according to temperature variation, by changing the period of the oscillation signal as a step function in inverse proportion to temperature. A temperature sensor(110) senses temperature in a semiconductor chip, and outputs an analog signal whose voltage level decreases according to the increase of temperature. An A/D converter(120) increases or decreases a value of a digital signal by comparing a level of the analog signal with a reference voltage. A decoder(130) outputs a decoding signal by comparing the amplitudes of the digital signal and a number of reference signals. An oscillation circuit(140) outputs a specific oscillation signal among a number of oscillation signals having different periods in response to the decoding signal. The decoder outputs the decoding signal to change the period of the oscillation signal as a step function in inverse proportion to the increase of temperature. |
