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LMT88

www.ti.com

SNIS175 – MARCH 2013

TYPICAL PERFORMANCE CHARACTERISTICS

PCB Layouts Used For Thermal Measurements

Figure 4. Layout Used For No Heat Sink Measurements

Figure 5. Layout Used For Measurements With Small Heat Sink

LMT88 TRANSFER FUNCTION

The LMT88 transfer function can be described in different ways with varying levels of precision. A simple linear

transfer function, with good accuracy near 25°C, is

(1)

Over the full operating temperature range of

−55°C to 130°C, best accuracy can be obtained by using the

parabolic transfer function.

(2)

solving for T:

(3)

A linear transfer function can be used over a limited temperature range by calculating a slope and offset that give

best results over that range. A linear transfer function can be calculated from the parabolic transfer function of

the LMT88. The slope of the linear transfer function can be calculated using the following equation:

m =

−7.76 × 10

(4)

where T is the middle of the temperature range of interest and m is in V/°C. For example for the temperature

T = 35°C

(5)

and

m =

−11.77 mV/°C

(6)

The offset of the linear transfer function can be calculated using the following equation:

(7)

where:

Using this procedure the best fit linear transfer function for many popular temperature ranges was calculated in

Table 2. As shown in Table 2 the error that is introduced by the linear transfer function increases with wider

temperature ranges.

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