TMP708AIDBVT datasheet(7/14 Pages) TI1

7 / 14 page

TMP708

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SBOS585A

– DECEMBER 2011 – REVISED FEBRUARY 2012

APPLICATION INFORMATION

SET-POINT RESISTOR (RSET)

The temperature threshold is set by connecting RSET from the SET pin to GND. The value of RSET can be

determined using either Figure 2 or from Equation 1:

RSET (kΩ) = 0.0012T

2 – 0.9308T + 96.147

Where T = temperature threshold in degree Celsius.

(1)

THERMAL CONSIDERATIONS

The TMP708 quiescent current is typically 40

μA. The device dissipates negligible power when the output drives

a high-impedance load. Thus, the die temperature is the same as the package temperature. In order to maintain

accurate temperature monitoring, a good thermal contact should be provided between the TMP708 package and

the device being monitored. The rise in die temperature as a result of self-heating is given by the following

equation:

ΔTJ = PDISS × θJA

Where:

PDISS = power dissipated by the device.

θJA = package thermal resistance. Typical thermal resistance for SOT-23 package is 217.9°C/W.

(2)

To limit the effects of self-heating, keep the output current at a minimum level.

POWER-SUPPLY FILTERING

Any significant noise on the VCC pin may result in a trip-point error. This noise can be minimized by low-pass

filtering the device supply (VCC) using a 150-Ω resistor and a 0.1-μF capacitor.

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