Semiconductor integrated circuit having a digital temperature sensor circuit

• US 5,835,553 A
• Filed: 04/22/1996
• Issued: 11/10/1998
• Est. Priority Date: 04/20/1995
• Status: Expired due to Fees

• Current Assignee: NEC Corporation
• Original Assignee: NEC Corporation
• Inventors: Suzuki, Naoshi
• Primary Examiner(s): Wambach, Margaret Rose
• Application Number:
  US08/635,676
• Time in Patent Office: 932 Days
• Field of Search: 377/25
• US Class Current: 377/25
• CPC Class Codes: G01K 1/02 Means for indicating or recording specially adapted for thermometers
• CPC Class Codes: G01K 7/245 in an oscillator circuit

Abstract

In a semiconductor integrated circuit, a temperature sensor circuit includes a pulse source for generating a count pulse and a resistor having a resistance changing dependently upon a temperature change. The temperature detecting circuit is configured to convert the change of the resistance of the resistor responding to the temperature change, into the pulse number of the count pulses, in response to each application of a temperature measuring signal having a first frequency, in order to generate a count signal. A counter counts the count signal and accumulates a count value for each temperature measuring signal so as to hold the accumulated count value. The counter outputs the accumulated count value in response to a reset signal having a second frequency lower than the first frequency. The counter is then reset by the reset signal.

Claims

1. A semiconductor integrated circuit comprising:

a temperature sensor circuit including a pulse source for generating a count pulse and a resistor having a resistance changing dependently upon a temperature change, said temperature sensor circuit being configured to convert the chance of the resistance of said resistor responding to said temperature change into a count pulse signal representative of said temperature chance in response to a temperature measuring signal having a first frequency; and

a counter counting said count pulse signal and accumulating a count value of said count pulse signal, said counter outputting and resetting the accumulated count value in response to a reset signal having a second frequency lower than said first frequency,

wherein said temperature sensor circuit includes;

a delay circuit having an RC time constant circuit composed of said resistor and a capacitor, said delay circuit outputting a delayed signal that includes a delay of said temperature measuring signal by a time corresponding to the time constant of said RC time constant circuit;

a clock generator for generating a clock signal of a third frequency higher than said first frequency, in synchronism with said temperature measuring signal; and

a gate circuit receiving said delayed signal and said clock signal, for generating said count pulse signal by passing said clock signal until said delayed signal is received.

2. A semiconductor integrated circuit claimed in claim 1 wherein said delay circuit includes an inverter consisting of series-connected first and second MOS transistors connected in series through said resistor between first and second power supply voltages, and said RC time constant circuit is connected to receive an output of the inverter.

3. A semiconductor integrated circuit claimed in claim 2 wherein said resistor comprises a diffused resistor having predetermined temperature coefficient.

4. A semiconductor integrated circuit claimed in claim 2 wherein said delay circuit includes a predetermined number of cascaded unitary delay circuits each of which further delays said temperature measuring signal.

5. A semiconductor integrated circuit claimed in claim 1 wherein said resistor comprises a diffused resistor having a predetermined temperature coefficient.

6. A method of sensing a temperature change, said method comprising the steps of:

issuing a temperature measuring signal at a first frequency;

supplying the temperature measuring signal through a temperature sensor circuit including a resistor having a resistance that changes in accordance with the temperature change;

converting a delay of the temperature measuring signal that was supplied through the temperature sensor circuit into a count pulse signal representative of the temperature change;

counting the count pulse signal;

accumulating a count value of the count pulse signal as an accumulated count value; and

outputting and resetting the accumulated count value in response to a reset signal having a second frequency lower than the first frequency.

7. A method of sensing a temperature change claimed in claim 6 wherein the step of converting includes the steps of:

generating a clock signal of a third frequency higher than the first frequency, in synchronism with the temperature measuring signal;

supplying the delayed signal and the clock signal to a gate circuit; and

passing the clock signal through the gate circuit until the delayed signal is received.