Temperature level detection circuit

• US 6,225,851 B1
• Filed: 04/19/2000
• Issued: 05/01/2001
• Est. Priority Date: 04/21/1999
• Status: Expired due to Term

• Current Assignee: EM Microelectronic - Marin SA (The Swatch Group AG)
• Original Assignee: EM Microelectronic - Marin SA (The Swatch Group AG)
• Inventors: Descombes, Arthur
• Primary Examiner(s): Callahan, Timothy P.
• Assistant Examiner(s): Nguyen, Hai L.
• Application Number:
  US09/552,248
• Time in Patent Office: 377 Days
• Field of Search: 327/77, 327/82, 327/512, 327/513, 327/574, 327/579, 327/585, 374/163, 374/170, 361/103, 257/53
• US Class Current: 327/512
• CPC Class Codes: G01K 3/005 Circuits arrangements for indicating a predetermined temperature fire detection G08B17/00
• CPC Class Codes: G01K 7/01 using semiconducting elements having PN junctions G01K7/02, G01K7/16, G01K7/30 take precedence

Abstract

The invention concerns a temperature level detection circuit including means (B1, B2, B3, 11, 12, 21, 31, 32) for generating diode voltages (V_BE1 to V_BE5) and calculating means including capacitive elements (51, 52, 53) and switching means (SW1 to SW4) arranged to connect selectively and sequentially, during first and second phases, the capacitive elements (51, 52, 53) to the means generating said diode voltages (V_BE1 to V_BE5). During the second phase, the calculating means generating a temperature signal representative of the temperature level being greater than or less than a determined temperature threshold (T_limit) defined as the temperature value for which the equation α₁(V_BE2−V_BE1)+α₂(V_BE3+α₃ (V_BE5−V_BE4)) becomes zero, where α₁, α₂, and α₃ are first, second and third proportionality coefficients determined by the values of the capacitive elements.

Claims

1. A temperature level detection circuit arranged to generate a temperature signal representative of said temperature level being greater than or less than a determined temperature threshold T_LIMIT, wherein said circuit includes:

means for generating diode voltages; and

calculating means for generating said temperature signal, these calculating means including capacitive elements and switching means arranged to connect selectively and sequentially, during a first and a second phase, said capacitive elements to said means for generating said diode voltages so that said calculating means generate said temperature signal during said second phase, said temperature threshold T_limit being defined as the temperature value for which the equation α

₁(V_BE2−

V_BE1) +α

₂(V_BE3+α

₃(V_BE5−

V_BE4)) becomes zero, where at, α

₂, and α

₃ are first, second and third proportionality coefficients determined by the values of said capacitive elements and V_BE1 to V_BE5 are first, second, third, fourth and fifth diode voltages, the third diode voltage being able to be equal to any one of the other diode voltages.

2. The detection circuit according to claim 1, wherein said calculating means are arranged to generate:

a first signal dependent of the temperature representative of the product by said first proportionality coefficient of the difference between the first and second diode voltages, and

a second signal independent of the temperature representative of the product by said second proportionality coefficient of the sum of said third diode voltage and the product by said third proportionality coefficient of the difference between said fourth and fifth diode voltages.

3. The detection circuit according to claim 2, wherein said calculating means are arranged to generate:

a third signal representative of the product of said third diode voltage by said second proportionality coefficient, and

a fourth signal representative of the product of the difference between said fourth and fifth diode voltages by said second and third proportionality coefficients;

these third and fourth signals being added to generate said second signal.

4. The detection circuit according to claim 3, wherein said calculating means include:

for generating said first signal, a first capacitive element of substantially equal capacitance to said first proportionality coefficient,

for generating said third signal, a second capacitive element of substantially equal capacitance to said second proportionality coefficient, and

for generating said fourth signal, a third capacitive element of substantially equal capacitance to the product of said second and third proportionality coefficients.

5. The detection circuit according to claim 1, wherein said means for generating said diode voltages include bipolar transistors connected in series with current sources and whose base is connected to the collector.

6. The detection circuit according to claim 4, wherein said means for generating said diode voltages include three bipolar transistors whose base is connected to the collector, a first and second of said transistors being each successively connected in series with two current sources, a third of said transistors being connected in series with a current source, the second and third transistor being substantially identical.

7. The detection circuit according to claim 4, wherein said means for generating said diode voltages include two bipolar transistors whose base is connected to the collector, each of said transistors being connected successively in series with two current sources.