Thermal sensors and methods of operating thereof

A thermal sensor comprising:

• a comparator haying a first and second input nodes;
• a reference voltage generator electrically coupled with the first input node of the comparator, the reference voltage generator being configured to provide a reference voltage that is substantially temperature-independent;
• and
• a complementary-to-absolute-temperature (CTAT) sensing circuit electrically coupled with the second input node of the comparator, the CTAT sensing circuit being configured to provide a temperature-dependent voltage, wherein the CTAT sensing circuit comprises:
• a current mirror;
• a first metal-oxide-semiconductor (MOS) transistor electrically coupled between the current mirror and ground, wherein a first node is between the first MOS transistor and the current mirror;
• a first resistor electrically coupled with the current mirror, wherein a second node is between the first resistor and the current mirror;
• and
• a second MOS transistor electrically coupled with the first resistor in series, wherein the second MOS transistor and the first resistor are electrically coupled with the first MOS transistor in a parallel fashion, and the first and second MOS transistors are operable in a sub-threshold region during a sensing operation of the thermal sensor.

A thermal sensor comprising:

• a comparator having a first and second input nodes;
• a reference voltage generator electrically coupled with the first input node of the comparator, the reference voltage generator being configured to provide a reference voltage that is substantially temperature-independent;
• and
• a proportional-to-absolute-temperature (PTAT) sensing circuit electrically coupled with the second input node of the comparator, the PTAT sensing circuit being configured to provide a temperature-dependent voltage, wherein the PTAT sensing circuit comprises:
• a current mirror;
• a first metal-oxide-semiconductor (MOS) transistor electrically coupled between the current mirror and ground, wherein a first node is between the first MOS transistor and the current mirror;
• a first resistor electrically coupled with the current mirror, wherein a second node is between the first resistor and the current mirror;
• and
• a second MOS transistor electrically coupled with the first resistor in series, wherein the second MOS transistor and the first resistor are electrically coupled with the first MOS transistor in a parallel fashion, and the first and second MOS transistors are operable in a sub-threshold region during a sensing operation of the thermal sensor.