Thermal Diodes

V

+

GND

LMT88

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SNIS175A – MARCH 2013 – REVISED JANUARY 2015

7 Detailed Description

7.1 Overview

The LMT88 device is a precision analog output CMOS integrated-circuit temperature sensor that operates over a

temperature range of

−55°C to 130°C . The power supply operating range is 2.4 V to 5.5 V. The transfer function

of LMT88 is predominately linear, yet has a slight predictable parabolic curvature. The accuracy of the LMT88

when specified to a parabolic transfer function is typically ±1.5°C at an ambient temperature of 30°C. The

temperature error increases linearly and reaches a maximum of ±5°C at the temperature range extremes. The

temperature range is affected by the power supply voltage. At a power supply voltage of 2.7 V to 5.5 V, the

temperature range extremes are 130°C and

−55°C. Decreasing the power supply voltage to 2.4 V changes the

negative extreme to

−30°C, while the positive remains at 130°C.

The LMT88 quiescent current is less than 10

μA. Therefore, self-heating is less than 0.02°C in still air. Shutdown

capability for the LMT88 is intrinsic because its inherent low power consumption allows it to be powered directly

from the output of many logic gates or does not necessitate shutdown at all.

The temperature sensing element is comprised of a simple base emitter junction that is forward biased by a

current source. The temperature sensing element is then buffered by an amplifier and provided to the OUT pin.

The amplifier has a simple class A output stage thus providing a low impedance output that can source 16 µA

and sink 1 µA.

7.2 Functional Block Diagram

7.3 Feature Description

7.3.1 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.

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