Granted Patent B2

US 8,369,170 · App. 13/053,727 · Granted Feb 5, 2013

Abstract

Claims (44)

1. A method for determining a temperature in a circuit comprising:

receiving a periodic signal, a frequency of the periodic signal being an increasing function of temperature;

determining a number of oscillations of the periodic signal during a time interval, a length of the time interval being an increasing function of temperature; and

determining the temperature based on the determined number of oscillations.

2. The method of claim 1 , wherein determining the temperature comprises decoding the number of oscillations according to a look-up table.

3. The method of claim 1 , wherein receiving a periodic signal comprises:

generating the periodic signal by a ring oscillator having a temperature dependent supply voltage; and

receiving the periodic signal from the ring oscillator.

4. The method of claim 3 , wherein the temperature-dependent supply voltage is generated by a temperature-dependent voltage generator.

5. The method of claim 4 , further comprising determining the length of the time interval by a timer.

6. The method of claim 5 , wherein determining the length of the time interval by the timer comprises receiving a time-out signal from the timer corresponding to the length of the time interval.

7. The method of claim 6 , wherein:

the temperature-dependent supply voltage is a first temperature-dependent supply voltage; and

determining the length of the time interval by the timer further comprises generating the time-out signal by the timer based on a second temperature-dependent supply voltage.

8. The method of claim 7 , wherein the second temperature-dependent supply voltage is generated based on the first temperature-dependent supply voltage.

9. The method of claim 1 , wherein determining the number of oscillations comprises:

enabling a counter;

receiving the periodic signal by the counter;

counting the number of oscillations of the periodic signal by the counter; and

disabling the counter after the time interval has elapsed.

10. The method of claim 1 , wherein determining the number of oscillations comprises:

enabling a shift register;

receiving the periodic signal by the shift register;

counting the number of oscillations of the periodic signal by the shift register; and

disabling the shift register after the time interval has elapsed.

11. A temperature detector in a circuit comprising:

an oscillator configured to generate a periodic signal, a frequency of the periodic signal being an increasing function of temperature;

a timer for determining a time interval, a length of the time interval being an increasing function of temperature; and

a recorder in electrical communication with the ring oscillator and the timer for determining a number of oscillations of the periodic signal during the timer interval.

12. The temperature detector of claim 11 , further comprising a look-up table stored in a memory for decoding a content of the recorder.

13. The temperature detector of claim 11 , wherein the recorder is a counter.

14. The temperature detector of claim 11 , wherein the recorder is a shift register.

15. The temperature detector of claim 11 , wherein the oscillator is a ring oscillator.

16. The temperature detector of claim 15 , further comprising:

a temperature-dependent voltage generator for supplying a first temperature-dependent supply voltage to the ring oscillator.

17. The temperature-dependent detector of claim 16 , wherein the temperature-dependent voltage generator further supplies a second temperature-dependent supply voltage to the timer.

18. The temperature detector of claim 17 , wherein:

the timer is configured to generate a time-out signal corresponding to the length of the time interval; and

the recorder is configured to receive the periodic signal from the oscillator and count a number of oscillations of the periodic signal during the timer interval.

19. The temperature detector of claim 18 , wherein the time-out signal is operative to disable the recorder at the end of the time interval.

20. A method for refreshing a dynamic random access memory (DRAM) comprising:

receiving a periodic signal, a frequency of the periodic signal being an increasing function of temperature;

determining a number of oscillations of the periodic signal during a time interval a length of the time interval being an increasing function of temperature; and

determining a refresh rate of the DRAM based on the determined number of oscillations.

Assignments (8)