Temperature measuring circuit

A temperature measuring circuit comprising:

• a capacitor configured to generate an inter-terminal voltage corresponding to an amount of stored electric charge;
• a first current supply configured to feed a first current;
• a second current supply configured to feed a second current;
• a first voltage supply configured to generate a first reference voltage;
• a second voltage supply configured to generate a second reference voltage;
• a third voltage supply configured to generate a third reference voltage corresponding to a temperature;
• a comparator circuit configured to output an output voltage indicating levels of two input voltages that are received;
• a first switch circuit configured to,
• upon receiving a first control signal, charge the capacitor through the first current and set the two input voltages at a selected reference voltage and the inter-terminal voltage, and
• upon receiving a second control signal, discharge the capacitor through the second current and set the two input voltages at the second reference voltage and the inter-terminal voltage;
• a second switch circuit configured to switch between a first connection state in which the selected reference voltage is set at the first reference voltage, and a second connection state in which the selected reference voltage is set at the third reference voltage;
• a control circuit configured to,
• during a first period, set a control signal at the second control signal in response to the output voltage indicating that the inter-terminal voltage is higher than the first reference voltage while the control signal is set at the first control signal and the second switch circuit is in the first connection state, and set the control signal at the first control signal and bring the second switch circuit into the first connection state in response to the output voltage indicating that the inter-terminal voltage is lower than the second reference voltage while the control signal is set at the second control signal, and
• during a second period, set the control signal at the second control signal in response to the output voltage indicating that the inter-terminal voltage is higher than the third reference voltage while the control signal is set at the first control signal and the second switch circuit is in the second connection state, and set the control signal at the first control signal and bring the second switch circuit into the second connection state in response to the output voltage indicating that the inter-terminal voltage is lower than the second reference voltage while the control signal is set at the second control signal;
• a counter circuit configured to count a first frequency of the control signal during the first period, and a second frequency of the control signal during the second period;
• and
• a temperature obtaining unit configured to obtain the temperature based on the first and second frequencies.