Datasheet

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DATASHEET

SMT172

last update

juni 1, 2015

reference

V10.0

page

1/9

Features and Highlights

 World’s most energy efficient temperature sensor

 Wide temperature range: -45 °C to 130 °C

 Extreme low noise: less than 0.001°C

 Low inaccuracy: 0.25°C (-10 °C to 100 °C)

0.1 °C (TO18)

 Ultra low current (60 µA active or 220 nA

average)

 Wide supply voltage range: 2.7 V to 5.5 V

 Excellent long term stability

 Direct interface with Microcontroller (MCU)

 Wide range of package options

Application

 Ultra low power applications: wearable electronics, wireless sensor networks

 Medical applications: body temperature monitoring

 Instrumentation: (Bio)chemical analysis, Precision equipment

 Environmental monitoring (indoor / outdoor)

 Industrial applications: process monitoring / controlling

Introduction

The SMT172 is an ultra-low power, high accuracy temperature sensor that combines the ease of use with

the world’s leading performance over a wide temperature range. Using the most recent advances in the

silicon temperature sensing technology, the SMT172 has applied some really sophisticated IC design

techniques as well as high-precision calibration methods, to achieve an absolute inaccuracy of less than

0.25°C in the range of -10 °C to 100 °C

The SMT172 operates with a supply voltage from 2.7 V to 5.5 V. The typical active current of only 60 µA, the

high speed conversion over 4000 outputs per second (at room temperature) and an extremely low noise

makes this sensor the most energy efficient temperature sensor in the world.

The SMT172 has a pulse width modulated (PWM) output signal, where the duty cycle is proportional to the

measured temperature value. This makes it possible that the sensor can interface directly to a MCU without

using an Analog-to-Digital Converter (ADC). Today, the hardware Timer in a MCU to read our PWM signal

has become available almost universally, fast in speed and low in cost. Therefore it is extremely easy for any

user to get started with this sensor and achieve a very quick time to market.

Summary of content (9 pages)

PAGE 1
last update juni 1, 2015 DATASHEET SMT172 reference V10.0 page 1/9 Features and Highlights World’s most energy efficient temperature sensor Wide temperature range: -45 °C to 130 °C Extreme low noise: less than 0.001°C Low inaccuracy: 0.25°C (-10 °C to 100 °C) 0.1 °C (TO18) Ultra low current (60 µA active or 220 nA average)1 Wide supply voltage range: 2.7 V to 5.
PAGE 2
last update juni 1, 2015 DATASHEET SMT172 reference V10.0 page 2/9 Absolute Maximum Rating TA= 25°C. All voltages are referenced to GND, unless otherwise noted. Power supply voltage -0.5 V to 7 V Output Pin load 50 mA ESD protection (HBM) +2000 V Junction temperature +200 °C Soldering temperature (SOIC, SOT) +260 °C (10 s) Specification TA= -45°C to 130°C, Vcc=2.7 V to 5.5 V, unless otherwise noted. Parameter Min Supply Voltage 2.7 Active current1 Average current Typ Max 5.
PAGE 3
last update juni 1, 2015 DATASHEET SMT172 reference V10.0 page 3/9 Output Signal According to tradition, the Smartec temperature sensors have a duty cycle (PWM) output that can be directly interfaced with a microcontroller without the use of extra components. The output is a square wave with a well-defined temperature-dependent duty cycle. In general, the duty cycle of the output signal is defined by a linear equation: = . + .
PAGE 4
last update juni 1, 2015 DATASHEET SMT172 reference V10.0 page 4/9 Understanding the specifications Sampling Noise From the theory of signal processing it can be derived that there is a fixed ratio between the sensor’s signal frequency, the sampling rate and the sampling noise. The sampling rate limits the measurement accuracy to: tp ,-- = 200 ./ 06.1 .
PAGE 5
last update juni 1, 2015 DATASHEET SMT172 reference V10.0 page 5/9 Typical Performance Characteristics Error (oC) Maximum Error Limits SMT172 SMT172 Maximum Error Limits Vcc (V) Inaccuracy vs. Temperature(TO18) Normalized Error vs. Supply Voltage Supply current vs.
PAGE 6
last update juni 1, 2015 DATASHEET SMT172 reference V10.0 page 6/9 Measurement with improved accuracy This addendum to the datasheet of the SMT172 provides information how a temperature can be measured with a higher accuracy than what is specified in the datasheet. How about There are two reasons why the accuracy of 0.25°C (-10°C>100°C) has been specified in the datasheet of the SMT172: 1. A linear equation, which is compatible with SMT160 has been used for duty cycle versus temperature.
PAGE 7
last update juni 1, 2015 DATASHEET SMT172 reference V10.0 page 7/9 To obtain the inaccuracy given above, a couple of aspects must be taken into account, like the way of measuring, energy efficiency and package induced errors. Please find below an overview. Measuring the duty cycle In general, measuring the duty cycle is relatively simple. The signal is sampled over a certain number of periods, and after that the duty cycle is calculated as the total high time divided by the total time interval.
PAGE 8
last update juni 1, 2015 DATASHEET SMT172 reference V10.0 page 8/9 When measuring temperature of solid or liquid targets, it helps to have a good thermal contact between the sensor and the target. This can be achieved with metals and thermal paste. When measuring air temperatures, it is important to isolate the sensor from the rest of the measurement system, so that the heating from the surrounding circuit components has only a small influence on the sensor temperature.
PAGE 9
last update juni 1, 2015 DATASHEET SMT172 reference V10.0 page 9/9 Packaging SOIC-8L 5.08 TO220 TO92 Pin 1 3.85 6.1 SM172 xxxx Pin Pin Pin Pin 1 2 7 8 SMT172 xxxx Vcc Power Down Gnd Out All sizes in mm Pin 5 0.41 1 2 3 1 3 2 1.27 metal backplate = GND HEC HEC TO18 2 C 1 2 3 2.5 2 3 1 Output + Vcc GND 1 8.