Temperature sensor for display driver circuit and operating method thereof

1. A temperature sensor provided in a circuit, comprising:

a reference voltage generating unit configured to output a reference voltage;

a proportional voltage generating unit configured to output a proportional voltage by using a complementary to absolute temperature (CTAT) current inversely proportional to a temperature of the circuit;

a comparison unit configured to output a flag voltage by comparing magnitudes of the reference voltage and the proportional voltage; and

a sensor control unit configured to control the reference voltage generating unit and the proportional voltage generating unit.

2. The temperature sensor of claim 1 , wherein the proportional voltage generating unit comprises:

a proportional to absolute temperature (PTAT) current unit configured to generate a PTAT current proportional to the temperature of the circuit;

a CTAT current unit configured to generate the CTAT current inversely proportional to the temperature of the circuit; and

a calculation unit configured to generate the proportional voltage using a value of the PTAT current and a value of the CTAT current,

wherein the CTAT current unit comprises a variable resistor whose resistance value is changed under a control of the sensor control unit.

3. The temperature sensor of claim 2 , wherein, when the circuit is set in a test mode to maintain a first temperature, the sensor control unit changes the resistance value of the variable resistor based on a comparison result between a voltage value of the proportional voltage corresponding to the first temperature and a trimming table value.

4. The temperature sensor of claim 1 , wherein the comparison unit outputs a first flag voltage when a voltage value of the proportional voltage is less than or equal to a voltage value of the reference voltage, and

outputs a second flag voltage for lowering the temperature of the circuit when the proportional voltage is greater than the reference voltage.

5. The temperature sensor of claim 1 , wherein the reference voltage generating unit has a plurality of preset reference voltages,

the sensor control unit generates a reference voltage control signal for selecting one reference voltage from among a plurality of reference voltages and transmits the reference voltage control signal to the reference voltage generating unit, and

the reference voltage generating unit outputs a voltage value of the reference voltage to increase or decrease based on the reference voltage control signal.

6. A display driver circuit, comprising:

a temperature sensor configured to control heat generation of the display driver circuit; and

a circuit control unit configured to perform an operation for lowering a temperature of the display driver circuit,

wherein the temperature sensor comprises:

a reference voltage generating unit configured to output a reference voltage;

a proportional voltage generating unit configured to output a proportional voltage by using a complementary to absolute temperature (CTAT) current inversely proportional to the temperature of the display driver circuit;

a comparison unit configured to output a flag voltage by comparing magnitudes of the reference voltage and the proportional voltage; and

a sensor control unit configured to control the reference voltage generating unit and the proportional voltage generating unit.

7. The display driver circuit of claim 6 , wherein the proportional voltage generating unit comprises:

a proportional to absolute temperature (PTAT) current unit configured to generate a PTAT current proportional to the temperature of the display driver circuit;

a CTAT current unit configured to generate the CTAT current inversely proportional to the temperature of the display driver circuit; and

a calculation unit configured to generate the proportional voltage using a value of the PTAT current and a value of the CTAT current,

wherein the CTAT current unit comprises a variable resistor whose resistance value is changed under a control of the sensor control unit.

8. The display driver circuit of claim 6 , wherein the comparison unit outputs a first flag voltage when a voltage value of the proportional voltage is less than or equal to a voltage value of the reference voltage, and

outputs a second flag voltage and transmits the second flag voltage to the circuit control unit when the proportional voltage is greater than the reference voltage.

9. The display driver circuit of claim 8 , wherein the circuit control unit lowers the temperature of the display driver circuit when receiving the second flag voltage.

10. The display driver circuit of claim 9 , wherein the circuit control unit resets the display driver circuit, transmits an error message to a host, displays an error message, or reduces a frame rate to lower the temperature.

11. The display driver circuit of claim 8 , wherein the circuit control unit determines a specific temperature corresponding to the reference voltage as a current temperature of the display driver circuit when receiving the first flag voltage.

12. A method for operating a display driver circuit having a temperature sensor, comprising:

setting a proportional voltage generating unit to output a first voltage when the display driver circuit is a first temperature;

controlling a reference voltage generating unit to output a reference voltage based on a temperature of the display driver circuit to be sensed;

outputting a first flag voltage when a proportional voltage output by the proportional voltage generating unit is less than or equal to the reference voltage and outputting a second flag voltage when the proportional voltage is greater than the reference voltage; and

lowering the temperature of the display driver circuit based on the second flag voltage,

wherein setting the proportional voltage generating unit comprises setting a resistance value of a variable resistor included in the proportional voltage generating unit such that the proportional voltage of the proportional voltage generating unit becomes the first voltage.

13. The method of claim 12 , wherein lowering the temperature of the display driver circuit comprises:

lowering the temperature of the display driver circuit, by resetting the display driver circuit, transmitting an error message to a host, displaying an error message, or reducing a frame rate.

14. The method of claim 12 , wherein setting the resistance value of the variable resistor comprises:

receiving a tester drive signal by a tester;

setting the display driver circuit as a test mode to maintain the first temperature; and

setting the resistance value of the variable resistor such that the proportional voltage becomes the first voltage based on a comparison result between a voltage value of the proportional voltage corresponding to the first temperature and a trimming table value.

15. The method of claim 12 , wherein controlling the reference voltage generating unit comprises:

selecting one reference voltage from among a plurality of preset reference voltages and setting the selected reference voltage as the reference voltage.

16. A method for sensing a temperature of a display driver circuit, comprising:

setting a reference voltage generating unit to select a reference voltage from among a plurality of preset reference voltages and output the reference voltage such that the reference voltage increases or decreases;

setting a proportional voltage generating unit to output a first voltage when the display driver circuit is at a first temperature;

outputting a first flag voltage when a proportional voltage output by the proportional voltage generating unit is less than or equal to the reference voltage, and outputting a second flag voltage when the proportional voltage is greater than the reference voltage; and

determining a temperature of the display driver circuit based on the first and second flag voltages,

wherein setting the proportional voltage generating unit comprises setting a resistance value of a variable resistor included in the proportional voltage generating unit such that the proportional voltage of the proportional voltage generating unit corresponds to the first voltage.

17. The method of claim 16 , wherein setting the resistance value of the variable resistor comprises:

receiving a tester drive signal from the tester;

setting the display driver circuit to test mode to maintain the first temperature; and

setting the resistance value of the variable resistor such that the proportional voltage corresponds to the first voltage based on a comparison result between a proportional voltage corresponding to the first temperature and a trimming table value.

18. The method of claim 16 , wherein determining the temperature of the display driver circuit comprises:

determining a specific temperature corresponding to the reference voltage output by the reference voltage generating unit as a current temperature of the display driver circuit when receiving the first flag voltage.