Ring oscillator for temperature sensor, temperature sensor circuit, and semiconductor device having the same

A temperature sensor circuit comprising:

• a ring oscillator having an odd number of unit circuits connected in series, each of the unit circuits comprising an inverter, and one or more FETs each of which is a temperature sensor and uses a drain-source leakage current in a state that the FET is normally turned off;
• a frequency-dividing circuit frequency-dividing one of an oscillation output of the ring oscillator and a predetermined clock;
• a counting circuit counting the other of the oscillation output of the ring oscillator and the predetermined clock in one cycle of an output of the frequency-dividing circuit;
• a first holding circuit holding an established upper limit value corresponding to an upper limit value of a substrate temperature;
• a comparing circuit comparing a count output of the counting circuit with the established upper limit value held by the first holding circuit, and outputting a first detection signal when the count output is larger than the established upper limit value;
• and
• a generation circuit generating a stop signal which stops to operate a circuit based on the first detection signal.

A temperature sensor circuit comprising:

• a ring oscillator having a plurality of unit circuits connected in series, each of the plurality of unit circuits comprising an inverter and a first FET being normally turned off, the ring oscillator being driven by a drain-source leakage current of the first FET;
• a frequency-dividing circuit frequency-dividing one of an oscillation output of the ring oscillator and a clock fed from outside;
• a counting circuit counting the other of the oscillation output of the ring oscillator and the clock in one cycle of an output of the frequency-dividing circuit;
• a first holding circuit holding an established upper limit value corresponding to an upper limit value of a substrate temperature;
• and
• a comparing circuit comparing a count output of the counting circuit with the established upper limit value held by the first holding circuit, and outputting a first detection signal when the count output is larger than the established upper limit value.

A semiconductor device comprising:

• a semiconductor substrate;
• a circuit block provided on the semiconductor substrate;
• and
• a temperature sensor circuit provided in the circuit block, the temperature sensor circuit further comprising:
• a ring oscillator having a plurality of unit circuits connected in series, each of the plurality of unit circuits comprising an inverter and a transistor being normally turned off, the ring oscillator being driven by a leakage current of the transistor;
• a frequency-dividing circuit frequency-dividing one of an oscillation output of the ring oscillator and a predetermined clock;
• a counting circuit counting the other of the oscillation output of the ring oscillator and the predetermined clock in one cycle of an output of the frequency-dividing circuit;
• a first holding circuit holding an established upper limit value corresponding to an upper limit value of a substrate temperature;
• a comparing circuit comparing a count output of the counting circuit with the established upper limit value held by the first holding circuit, and outputting a first detection signal when the count output is larger than the established upper limit value;
• and
• a generation circuit generating a stop signal which stops to operate the circuit block based on the first detection signal.

A semiconductor device comprising:

• a semiconductor substrate;
• a circuit block provided on the semiconductor substrate;
• and
• a temperature sensor circuit provided on the semiconductor substrate, the temperature sensor circuit further comprising:
• a ring oscillator having an inverter and a transistor being normally turned off, and being driven by a leakage current of the transistor;
• a counting circuit counting an oscillation output of the ring oscillator;
• a first holding circuit holding an established upper limit value corresponding to a first temperature;
• a first comparing circuit comparing a count output of the counting circuit with the established upper limit value, and outputting a first detection signal when the count output is larger than the established upper limit value;
• a second holding circuit holding an established lower limit value corresponding to a second temperature which is lower than the first temperature;
• a second comparing circuit comparing the count output with the established lower limit value, and outputting a second detection signal when the count output is larger than the established lower limit value;
• and
• a generation circuit generating a stop signal which stops to operate the circuit block based on the first detection signal.