Temperature indicator circuit with temperature hysteresis

An apparatus including an integrated circuit with a temperature indicator circuit having temperature hysteresis, said integrated circuit comprising:

• a substrate which includes a functional circuit integrated therein;
• a temperature sensing circuit, integrated within said substrate, configured to measure a temperature of said substrate and in accordance therewith provide first and second temperature signals which vary in respective relations to said measured temperature;
• a reference signal circuit, integrated within said substrate, configured to provide a reference signal which corresponds to a reference temperature;
• a first signal comparison circuit, integrated within said substrate and coupled to said reference signal circuit and said temperature sensing circuit, configured to receive and compare said reference signal and said first temperature signal and in accordance therewith provide a first comparison signal with first and second signal states, wherein
• said first signal state indicates when said first comparison signal has a first signal polarity relative to said reference signal,
• said second signal state indicates when said first comparison signal has a second polarity relative to said reference signal and opposite to said first signal polarity, and
• said first comparison signal transitions between said first and second signal states at a first approximate value of said measured temperature;
• a second signal comparison circuit, integrated within said substrate and coupled to said reference signal circuit and said temperature sensing circuit, configured to receive and compare said reference signal and said second temperature signal and in accordance therewith provide a second comparison signal with third and fourth signal states, wherein
• said third signal state indicates when said second comparison signal has a third signal polarity relative to said reference signal,
• said fourth signal state indicates when said second comparison signal has a fourth polarity relative to said reference signal and opposite to said third signal polarity, and
• said second comparison signal transitions between said third and fourth signal states at a second approximate value of said measured temperature which is higher than said first measured approximate temperature value;
• and
• a signal state indicating circuit, integrated within said substrate and coupled to said first and second signal comparison circuits, configured to receive said first and second comparison signals and in accordance therewith provide a state signal indicating a time which follows an increase in said measured temperature above said second approximate value and precedes a decrease in said measured temperature below said first approximate value.

A method of indicating temperature with temperature hysteresis, comprising the steps of:

• receiving a reference signal which corresponds to a reference temperature;
• receiving first and second temperature signals which vary in respective relations to a measured temperature;
• comparing said reference signal and said first temperature signal and in accordance therewith generating a first comparison signal with first and second signal states by
• generating said first signal state when said first comparison signal has a first signal polarity relative to said reference signal,
• generating said second signal state when said first comparison signal has a second polarity relative to said reference signal and opposite to said first signal polarity, and
• transitioning said first comparison signal between said first and second signal states at a first approximate value of said measured temperature;
• comparing said reference signal and said second temperature signal and in accordance therewith generating a second comparison signal with third and fourth signal states by
• generating said third signal state when said second comparison signal has a third signal polarity relative to said reference signal,
• generating said fourth signal state when said second comparison signal has a fourth polarity relative to said reference signal and opposite to said third signal polarity, and
• transitioning said second comparison signal between said third and fourth signal states at a second approximate value of said measured temperature which is higher than said first measured approximate temperature value;
• and
• receiving said first and second comparison signals and in accordance therewith generating a state signal indicating a time which follows an increase in said measured temperature above said second approximate value and precedes a decrease in said measured temperature below said first approximate value.

A method of indicating the temperature of an integrated circuit with temperature hysteresis, comprising the steps of:

• measuring, within a substrate which includes a functional circuit integrated therein, a temperature of said substrate and in accordance therewith generating first and second temperature signals which vary in respective relations to said measured temperature;
• generating, within said substrate, a reference signal which corresponds to a reference temperature;
• comparing, within said substrate, said reference signal and said first temperature signal and in accordance therewith generating a first comparison signal with first and second signal states by
• generating said first signal state when said first comparison signal has a first signal polarity relative to said reference signal,
• generating said second signal state when said first comparison signal has a second polarity relative to said reference signal and opposite to said first signal polarity, and
• transitioning said first comparison signal between said first and second signal states at a first approximate value of said measured temperature;
• compare, within said substrate, said reference signal and said second temperature signal and in accordance therewith generating a second comparison signal with third and fourth signal states by
• generating said third signal state when said second comparison signal has a third signal polarity relative to said reference signal,
• generating said fourth signal state when said second comparison signal has a fourth polarity relative to said reference signal and opposite to said third signal polarity, and
• transitioning said second comparison signal between said third and fourth signal states at a second approximate value of said measured temperature which is higher than said first measured approximate temperature value;
• and
• receiving said first and second comparison signals and in accordance therewith generating, within said substrate, a state signal indicating a time which follows an increase in said measured temperature above said second approximate value and precedes a decrease in said measured temperature below said first approximate value.