TMP64 datasheet(13/16 Pages) TI1

13 / 16 page

Temperature (qC)

100

125

150

D014

RBias

94 k

5 V

RTMP64

200 k

VOut

10 k

200 k

VTemp

RFB

300 k

VRef

TMP64

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SNIS212 – DECEMBER 2019

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Typical Application (continued)

Figure 11. Thermal Foldback Using TMP64 Voltage Divider and a Rail-to-Rail Op Amp

The op amp remains high as long as the voltage output is below VRef. When the temperature goes above 110 °C,

then the output swings low to the 0-V rail of the op amp. The rate at which the foldback occurs is dependent on

the feedback network, RFB and R1, which varies the gain of the op amp, G, given by Equation 6. This in return

controls the voltage/temperature sensitivity of the circuit. This voltage output is fed into a LED driver IC that

adjusts output current accordingly. The final output voltage used for thermal foldback is VOUT, and is given in

Equation 7. In this example where the knee point is set at 110 °C, the output voltage curve is as shown in

Figure 12.

(5)

(6)

(7)

Figure 12. Thermal Foldback Voltage Output Curve

TMP64 Datasheet(PDF) 13 Page - Texas Instruments