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TMP61

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SBOS921C – DECEMBER 2018 – REVISED SEPTEMBER 2019

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Typical Application (continued)

(6)

Figure 17. TMP61 Thermal Compensation Circuit

9.2.1.2.2

Thermal Protection With Comparator

The engineer can use the TMP61, a voltage reference, and a comparator to program the thermal protection. As

shown in Figure 18, the output of the comparator will remain low until the voltage of the thermistor divider, with

comparator signals an overtemperature warning signal. The engineer can also program the hysteresis to prevent

the output from continuously toggling around the temperature threshold when the output returns low. Either a

comparator with built-in hysteresis or feedback resistors may be used.

Figure 18. Temperature Switch Using TMP61 Voltage Divider and a Comparator

9.2.1.2.3

Thermal Foldback

One application that uses the output voltage of the TMP61 in an active control circuit is thermal foldback. This is

performed to reduce, or fold back, the current driving a string of LEDs, for example. At high temperatures, the

LEDs begin to heat up due to environmental conditions and self-heating. Thus, at a certain temperature threshold

based on the LED's safe operating area, the driving current must be reduced to cool down the LEDs and prevent

thermal runaway. The TMP61 voltage output increases with temperature when the output is in the lower position

of the voltage divider, and can provides a response used to fold back the current. Typically, the current is held at

a specified level until a high temperature is reached, known as the knee point, where the current must be rapidly