R1

4.1V

R3

R2

0.1 2F

U3

LM4040

R4

VOUT

V+

VT

VTemp

+

-

U1

LM20

V+

U2

(High = overtemp alarm)

LM7211

LM20

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SNIS106Q – DECEMBER 1999 – REVISED JANUARY 2015

Table 4. Output Voltage vs Temperature

Temperature (T)

Typical VO

130°C

303 mV

100°C

675 mV

80°C

919 mV

30°C

1515 mV

25°C

1574 mV

0°C

1863.9 mV

–30°C

2205 mV

−40°C

2318 mV

−55°C

2485 mV

8.2.1.3 Application Curve

Figure 6. Output Voltage vs Temperature

8.2.2 Centigrade Thermostat

Figure 7. Centigrade Thermostat

8.2.2.1 Design Requirements

A simple thermostat can be created by using a reference (LM4040) and a comparator (LM7211) as shown in

Figure 7.

8.2.2.2 Detailed Design Procedure

The threshold values can be calculated using Equation 12 and Equation 13.

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