THERMAL SENSOR SYSTEM AND METHOD BASED ON CURRENT RATIO

• US 20140086279A1
• Filed: 09/27/2012
• Published: 03/27/2014
• Est. Priority Date: 09/27/2012
• Status: Active Grant

• Current Assignee: NXP USA, Inc. (NXP Semiconductors NV)
• Original Assignee: Freescale Semiconductor, Inc. (NXP Semiconductors NV)
• Inventors: Cao, Lipeng, Jokinen, Tommi M., Mai, Khoi, Sanchez, Hector
• Granted Patent: US 9,316,542 B2
• Time in Patent Office: Days
• US Class Current: 374/183
• CPC Class Codes: G01K 1/026 arrangements for monitoring a plurality of temperatures, e.g. by multiplexing
• CPC Class Codes: G01K 7/01 using semiconducting elements having PN junctions G01K7/02, G01K7/16, G01K7/30 take precedence

Abstract

A thermal sensor system including at least one thermal sensor, a voltage control network, a current gain network, a current compare sensor, and a controller. The voltage control network applies reference and delta voltage levels to a thermal sensor, which develops reference and delta current signals. The current gain network is used to adjust current gain. The current compare sensor is responsive to the reference and delta current signals and provides a comparison metric. The controller selects a temperature subrange and controls the current gain network to adjust the gain of the delta current signal to determine a gain differential value indicative of the temperature. The controller may select from among different sized thermal sensors, current mode gain values, and control voltages corresponding with each of multiple temperature subranges. Any one or more of these parameters may be adjusted to adjust an operating point for selecting a corresponding temperature subrange.

Claims

1. A thermal sensor system, comprising:

at least one thermal sensor;

a voltage control network which applies a reference voltage level and a corresponding delta voltage level to said at least one thermal sensor, wherein said at least one thermal sensor responsively develops a reference current signal and a corresponding delta current signal;

a current gain network configured to adjust gain of said delta current signal relative to said reference current signal;

a current compare sensor responsive to said reference current signal and said delta current signal which is configured to provide a comparison metric;

a controller which is configured to select said reference voltage level and said delta voltage level from among a plurality of reference voltage levels and a corresponding plurality of delta voltage levels, wherein said selected reference and delta voltage levels correspond with a selected one of a plurality of temperature subranges; and

wherein said controller is further configured to control said current gain network to adjust gain of said delta current signal while monitoring said comparison metric to determine a gain differential value indicative of a current ratio of said reference current signal and said delta current signal, and wherein said controller determines a temperature value based on said gain differential value.

2. The thermal sensor system of claim 1, wherein said controller is configured to search said plurality of temperature subranges from highest to lowest until a valid gain differential value is obtained.

3. The thermal sensor system of claim 1, wherein for at least one of said plurality of temperature subranges, said controller is configured to apply said selected reference voltage level to said at least one thermal sensor and to program said current gain network with an initial gain value to determine a reference comparison metric, and then to apply said delta voltage level to said at least one thermal sensor and then to adjust gain of said current gain network until said comparison metric substantially matches said reference comparison metric to provide a final gain metric, and then to determine said gain differential value as a difference between said final gain value and said initial gain value.

4. The thermal sensor system of claim 1, wherein:

said current gain network comprises at least one mode gain block and at least one search gain block; and

wherein said controller is configured to program said at least one mode gain block based on said selected one of said plurality of temperature subranges and to further adjust gain of said at least one search gain block to determine said gain differential value.

5. The thermal sensor system of claim 1, wherein:

said at least one thermal sensor comprises a plurality of different sized thermal sensors; and

wherein said controller is configured to select from among said plurality of different sized thermal sensors to select a thermal sensor which corresponds with said selected one of said plurality of temperature subranges.

6. The thermal sensor system of claim 5, wherein:

said current gain network comprises at least one mode gain block and at least one search gain block; and

wherein said controller is further configured to program said at least one mode gain block based on said selected one of said plurality of temperature subranges and to further adjust gain of said at least one search gain block to determine said gain differential value.

7. The thermal sensor system of claim 1, further comprising:

said current compare sensor comprising a voltage controlled oscillator responsive to said reference current signal and said delta current signal for providing an oscillator signal as said comparison metric;

an oscillation detect circuit which senses whether said oscillator signal is oscillating and which provides a frequency sense signal indicative thereof; and

wherein said controller is configured to search said plurality of temperature subranges from highest to lowest until a valid gain differential value is obtained, and to advance to a next lower temperature subrange when said frequency sense signal indicates non-oscillation of said oscillator signal.

8. The thermal sensor system of claim 1, wherein:

said current compare sensor comprises a voltage controlled oscillator responsive to said reference current signal and said delta current signal for providing an oscillator signal as said comparison metric; and

wherein for at least one of said plurality of temperature subranges, said controller is configured to apply said selected reference voltage level to said at least one thermal sensor and to program said current gain network with an initial gain value to determine a reference period of said oscillator signal, and then to apply said delta voltage level to said at least one thermal sensor and then to adjust gain of said current gain network until an updated period of said oscillator signal substantially matches said reference period to provide a final gain metric, and then to determine said gain differential value as a difference between said final gain value and said initial gain value.

9. The thermal sensor system of claim 1, further comprising:

a memory storing a plurality of temperature values including one temperature value for each of a plurality of gain values; and

wherein said controller is configured to use said gain differential value to retrieve a corresponding temperature value from said memory.

10. The thermal sensor system of claim 1, further comprising:

a memory storing a plurality of temperature values including one temperature value for each of a plurality of gain values;

said controller is configured to retrieve a pair of temperature values and a corresponding pair of gain values from said memory closest to said gain differential value; and

wherein said controller is configured to interpolate a measured temperature value from said at least one temperature value and said at least one corresponding gain value.

11. A method of measuring temperature, comprising:

selecting one of a plurality of temperature subranges;

selecting a reference voltage level and a delta voltage level which correspond with the selected temperature subrange;

applying the selected reference voltage level and the selected delta voltage level to at least one thermal sensor which responsively develops a reference current signal and a delta current signal;

comparing the reference current signal and the delta current signal and providing a comparison metric;

adjusting a gain of the delta current signal until it substantially matches the reference current signal as indicated by the comparison metric and determining a gain differential; and

determining a temperature value based on the gain differential.

12. The method of claim 11, wherein said selecting one of a plurality of temperature subranges comprises selecting from among the plurality of temperature subranges from highest to lowest until a valid gain differential is determined.

13. The method of claim 11, for at least one of the plurality of temperature subranges, further comprising:

applying an initial gain value with application of the selected reference voltage level and determining a reference comparison metric;

wherein said adjusting gain comprises adjusting gain from the initial gain value with application of the selected delta voltage level until an adjusted comparison metric substantially matches the reference comparison metric for determining a final gain value; and

wherein said determining a gain differential comprises determining a difference between the final gain value and the initial gain value.

14. The method of claim 11, further comprising:

selecting a mode gain which corresponds with the selected temperature subrange; and

wherein said adjusting a gain of the delta current signal comprises adjusting a search gain relative to an initial search gain value.

15. The method of claim 11, further comprising selecting a thermal sensor from a plurality of thermal sensors which has a size corresponding with the selected temperature subrange.

16. The method of claim 11, further comprising:

selecting a thermal sensor having a size corresponding with the selected temperature subrange;

selecting a mode gain which corresponds with the selected temperature subrange; and

wherein said adjusting a gain of the delta current signal comprises adjusting a search gain relative to an initial search gain value.

17. The method of claim 11, further comprising:

said selecting one of a plurality of temperature subranges comprises selecting from among the plurality of temperature subranges from highest to lowest until a valid gain differential is determined;

said providing a comparison metric comprising providing an oscillator signal;

detecting whether the oscillator signal is oscillating and providing a frequency sense signal indicative thereof; and

advancing to a next lower temperature subrange when the frequency sense signal indicates non-oscillation of the oscillator signal.

18. The method of claim 11, wherein for at least one of the plurality of temperature subranges, comprising:

said providing a comparison metric comprising providing an oscillator signal;

applying an initial gain value with application of the selected reference voltage level and determining a reference period of the oscillator signal;

wherein said adjusting gain comprises adjusting gain from the initial gain value with application of the selected delta voltage level until an adjusted period of the oscillator signal substantially matches the reference period for determining a final gain value; and

wherein said determining a gain differential comprises determining a difference between the final gain value and the initial gain value.

19. The method of claim 11, wherein said determining a temperature value comprises retrieving a temperature value from a memory that corresponds with the determined gain differential.

20. The method of claim 11, wherein said determining a temperature value comprises retrieving a plurality of temperature values and corresponding gain values from a memory and interpolating a measured temperature value.

21. A thermal sensor system, comprising:

a plurality of different sized thermal sensors;

a controller which is configured to select from among said plurality of different sized thermal sensors to select a thermal sensor having a size which corresponds with a selected one of a plurality of temperature subranges;

a voltage control network which applies a reference voltage level and a corresponding delta voltage level to said selected thermal sensor, wherein said selected thermal sensor responsively develops a reference current signal and a corresponding delta current signal;

a current gain network configured to adjust gain of said delta current signal relative to said reference current signal;

a current compare sensor responsive to said reference current signal and said delta current signal which is configured to provide a comparison metric; and

wherein said controller is further configured to control said current gain network to adjust gain of said delta current signal while monitoring said comparison metric to determine a gain differential value indicative of a current ratio of said reference current signal and said delta current signal, and wherein said controller determines a temperature value based on said gain differential value.