Temperature-sensing circuit and operating method thereof
A temperature-sensing circuit is provided, which includes: a search-control circuit, a voltage-reference circuit, a CTAT (complementary to absolute temperature) circuit, a digital-to-analog converter (DAC) circuit, a comparison circuit, and an SAR (successive approximation register) circuit. The search-control circuit generates a reference-voltage selection signal according to a plurality of control signals. The voltage-reference circuit selects a first reference voltage from a plurality of candidate reference voltages according to the reference-voltage selection signal, and provides a second reference voltage. The CTAT circuit converts the second reference voltage into a first comparison voltage. The DAC circuit converts the first reference voltage into a second comparison voltage. The comparison circuit compares the first comparison voltage and the second comparison voltage to generate a comparison-result signal. The SAR control circuit outputs each bit of a temperature-segment signal of an operating temperature according to the comparison-result signal. The control signals include the temperature-segment signal.
1. A temperature-sensing circuit, comprising:
a search-control circuit, configured to generate a reference-voltage selection signal according to a plurality of control signals;
a voltage-reference circuit, configured to select a first reference voltage from a plurality of candidate reference voltages according to the reference-voltage selection signal, and provide a second reference voltage;
a CTAT (complementary to absolute temperature) circuit, configured to convert the second reference voltage into a first comparison voltage;
a digital-to-analog converter circuit, configured to convert the first reference voltage into a second comparison voltage;
a comparison circuit, configured to compare the first comparison voltage and the second comparison voltage to generate a comparison-result signal; and
an SAR (successive approximation register) control circuit, configured to output each bit of a temperature-segment signal of an operating temperature of the temperature-sensing circuit according to the comparison-result signal,
wherein the control signals comprise the temperature-segment signal.
2. The temperature-sensing circuit as claimed in claim 1 , wherein the voltage-reference circuit is a bandgap voltage reference circuit.
3. The temperature-sensing circuit as claimed in claim 2 , wherein the voltage-reference circuit comprises a multiplexer to select the first reference voltage from the candidate reference voltages according to the reference-voltage selection signal.
4. The temperature-sensing circuit as claimed in claim 1 , wherein the SAR control circuit uses a modified binary-search method to sequentially output each bit of the temperature-segment signal,
wherein during the sequential outputting of each bit of the temperature-segment signal, when one or more predetermined most significant bits in the temperature-segment signal meet a predetermined condition, the search-control circuit changes the reference-voltage selection signal to control the voltage-reference circuit to adjust the first reference voltage.
5. The temperature-sensing circuit as claimed in claim 4 , wherein the control signals further comprise a sequencing-control signal, a segment signal, an increment-control signal, and a decrement-control signal,
wherein the sequencing-control signal controls order of each bit of the temperature-segment signal, and the segment signal indicates a specific temperature region to be adjusted in the temperature-sensing circuit,
wherein the increment-control signal and the decrement-control signal represent increasing and decreasing an amplitude magnification factor of the first reference voltage.
6. The temperature-sensing circuit as claimed in claim 5 , wherein the predetermined condition indicates that one or more most significant bits in the temperature-segment signal comply with the segment signal.
7. The temperature-sensing circuit as claimed in claim 5 , wherein the search-control circuit comprises a lookup table for recording relationships between the sequencing-control signal, the segment signal, the increment-control signal, the decrement-control signal, and the reference-voltage selection signal.
8. The temperature-sensing circuit as claimed in claim 7 , wherein the lookup table is implemented by a programmable logic array, a complex programmable logic device, a processor, a microcontroller, or an application-specific integrated circuit.
9. The temperature-sensing circuit as claimed in claim 1 , wherein the SAR control circuit comprises a sequencing-control circuit, a one-shot circuit, and an SAR circuit,
wherein the one-shot circuit receives a clock signal to generate a latch signal, and the sequencing-control circuit receives the clock signal to sequentially generate the sequencing-control signal corresponding to each bit of the temperature-segment signal.
10. The temperature-sensing circuit as claimed in claim 9 , wherein the SAR circuit generates the temperature-segment signal and a digital-to-analog conversion signal according to the comparison-result signal, the sequencing-control signal, and the latch signal.
11. The temperature-sensing circuit as claimed in claim 10 , wherein the digital-to-analog conversion signal is input to the digital-to-analog converter circuit to convert the first reference voltage into the second comparison voltage.
12. The temperature-sensing circuit as claimed in claim 1 , wherein the digital-to-analog converter circuit is a resistive digital-to-analog converter circuit.