LMT70

Thermal Diodes

TAO

VDD

GND

T_ON

LMT70, LMT70A

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SNIS187A – MARCH 2015 – REVISED JULY 2015

9 Detailed Description

9.1 Overview

The LMT70 is a precision analog output temperature sensor. It includes an output switch that is controlled by the

T_ON digital input. The output switch enables the multiplexing of several devices onto a single ADC input thus

expanding on the ADC input multiplexer capability.

The temperature sensing element is comprised of simply stacked BJT base emitter junctions that are biased by a

current source. The temperature sensing element is then buffered by a precision amplifier before being

connected to the output switch. The output amplifier has a simple class AB push-pull output stage that enables

the device to easily source and sink current.

9.2 Functional Block Diagram

9.3 Feature Description

9.3.1 Temperature Analog Output (TAO)

The TAO push-pull output provides the ability to sink and source current. This is beneficial when, for example,

driving dynamic loads like an input stage on an analog-to-digital converter (ADC). In these applications the

source current is required to quickly charge the input capacitor of the ADC. See the Typical Application section

for more discussion of this topic. The LMT70 is ideal for this and other applications which require strong source

or sink current.

9.3.1.1 LMT70 Output Transfer Function

The LMT70 output voltage transfer function appears to be linear, but upon close inspection it can be seen that it

is truly not linear and can be better described by a second or third order transfer function equation.

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